Biology

BIOLOGY

Chapter 2 Cell structure and

organization

Cell

 The basic unit of life

 Extremely small (10 – 20 microns)

 Made up of living material called protoplasm consisting of water, proteins, carbohydrates and fats

 Contains many compartments called organelles

Organelles

 Cellulose cell wall

o Present in plant cells

o Rigid outermost layer of plant cells which provide mechanical support o Prevents plant cell from bursting when absorbing water

o Made up of cellulose, a type of carbohydrate o Fully permeable

o Gives the cell a fixed shape due to its rigidity  Cell surface membrane

o Present in plant and animal cell

o Made up of a double layer of phospholipids with some carbohydrates and proteins o Forms boundary of cell

o Outermost layer in animal cell and is located beneath the cell wall in plant cells o Partially permeable

 Nucleus

o Present in both plant and animal cells o Controls all cellular activities

o Darkly stained, prominent in microscopic slide images

o Most cells have diploid nucleus. Sex cells have haploid nucleus. Red blood cells do not have a nucleus

 Cytoplasm

o Present in plant and animal cells

o Contain organelles such as nucleus and mitochondria and more o Site where most cell activities occur

Nucleus contains

o Nuclear envelope

 separates the contents of the nucleus from the rest of the cytoplasm o Nucleoplasm,

 the dense material within the nucleus o Nucleolus

 plays a part in protein synthesis by producing ribosomes o Chromatin

 a mass of long thin thread-like structure made up of proteins and a compound called deoxyribonucleic acid (DNA)

Cytoplasm contains:

 Endoplasmic reticulum (ER)

o Present in both plant and animal cells

o Involved in lipid synthesis and breakdown of toxins

o System of membranes inside the cell which is continuous with the nuclear membrane

o Divided into 2 components – rough ER (RER) and smooth ER (SER)  RER

 A sheet-like structure with surface studded with ribosomes  Involved in protein synthesis and modifications

 SER

 Tube-like structure and its surface does not have ribosomes  Synthesises fats and steroids

 Converts harmful substances into harmless substances in a process called detoxification

o Sheet-like and tube-like structures of RER and SER increases its surface area to volume ratio to carry out their functions more efficiently

 Ribosomes

o Present in both plant and animal cells

o Made up of proteins and ribonucleic acid (RNA)

o Small, spherical and numerous. Mainly concentrated on the RER surface, but some lie freely in the cytoplasm

o Make polypeptides from amino acids which eventually form proteins o Make proteins used within the cytoplasm of the cell

o RER transports proteins made by ribosomes to the golgi apparatus for secretion out of the cell

o Present in both plants and animal cells

o Made up of several stacks of curved flattened membranes arragned in sacs called cisternae

o Membranes are usually surrounded by spherical bodies called vesicles o Vesicles transport immature proteins made in RER to Golgi body for further

processing

o Chemically modifies substances made in ER

o Stores and packages these substances in vesicles for secretion out of the cell o Set of membranes that make up Golgi body is not continuous with nuclear

membrane or ER

 Vesicles get pinched off RER, fuses with Golgi body, and substances in vesicles released into golgi body

 Golgi apparatus may modify these substances

 Secretory vesicles containing this modified substances pinched off Golgi apparatus and fuse with cell surface membrane to be released out of the cell  Mitochondria (singular mitochondrion)

o Present in both plant and animal cells

o Small oval shaped organelle which are the powerhouse of the cell

o Aerobic respiration occurs in mitochondria, food substances are oxidised to release energy in the form of adenosine triphosphate (ATP)

o ATP used by cell to perform cell activities such as growth and reproduction o Has 2 layers of membrane, inner membrane highly folded into structures called

cristae

o Cells that require more energy usually have more mitochondria  Chloroplasts

o Present only in plant cells

o Contain a green pigment called chlorophyll, which is essential for photosynthesis o Cells in the leaves of the plant usually has highest concentration of chloroplasts  Vacuoles

o Present in both plants and animal cells o Fluid-filled space enclosed by a membrane

o Animal cells contain numerous small vacuoles that contain water and food substances t

o These vacuoles exist temporarily

o Plant cells have a large central vacuole containing water and a liquid called cell sap o Cell sap contains dissolve substances such as sugars, mineral salts and amino acids o This large vacuole is enclosed by a partially permeable membrane called tonoplast Specialised cells, tissues, organs and systems

 Red blood cell (RBC)

o Most abundant cell type in blood (45 % of total vol. of blood)

o Contains haemoglobin which binds reversibly to oxygen and transport it to other parts of the body

o Absence of nucleus allows RBC to carry more haemoglobin

o Biconcave shape increases surface area to volume ratio to absorb oxygen at a faster rate

o Flexible enough to squeeze through blood capillaries  Root hair cell

o Lines the outer surface of plant roots

o Has a long finger-like projection along its length to increase its surface area to volume ratio for faster rate of water and mineral absorption

o Central vacuole contains concentrated cell sap, decreasing vacuole’s water

potential. More water can be absorbed by osmosis, as water moves from a region of higher water potential (the soil) to a region of lower concentration (the root cell) o Does not contain chloroplasts as it is usually not exposed to sunlight, hence does

not need to photosynthesise  Xylem vessel

o Transports water and dissolved minerals from plant roots to leaves o Made up of dead cells with thick walls

o Narrow and have no cross walls to obstruct water flow through the lumen o No protoplasm to offer resistance to water flow

o Walls are thickened with lignin to prevent collapse of the vessel o Xylem vessel provides mechanical support for plants

Cells, tissues, organs and systems

 Group of similar cells working together to perform a specific function is a tissue

 Simple tissues are made up of cells of the same type. Complex tissues are made up of more than one type of cell

 Different tissues combine to form an organ

 Organs work together in organ systems. A multi-cellular organism is made up of many organ systems working together

Chapter 3 Movement of substances

 Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient

 Occurs passively, no external energy needed

 Takes place as long as a concentration gradient is present, even through a partially permeable membrane

 Rate of diffusion depends on concentration gradient, size of diffusing substance and temperature

o Higher concentration gradient, faster diffusion rate o Bigger particle, lower diffusion rate

o Higher temperature, higher diffusion rate

 E.g. of diffusion

o Movement of oxygen and carbon dioxide between alveoli and blood capillaries in lungs

Osmosis

 Osmosis is the net movement of water particles from a region of higher water potential to a region of lower water potential down a water potential gradient across a partially permeable membrane

 Occurs passively

 Takes place only through a partially permeable membrane

Terminology Description

Isotonic 2 solutions are isotonic with respect to each other if they have equal water potential

Hypertonic A solution is hypertonic with respect to the other if it has lower water potential (lower water potential) Hypotonic A solution is hypotonic with respect

to the other if it is less concentrated (higher water potential)

 A solution that contains more dissolved substances has a lower water potential than a solution with less dissolved substances

Hypotonic solution

Isotonic solution Hypertonic solution

into cell. Cell eventually ruptures cell. Cell becomes crenated Plant cell Entry of water

into the cell. Cell becomes turgid

No change Water exits the cell.

Cell becomes flaccid, then plasmolysed

Active transport

 Movement of substances from a region of lower concentration to a region of higher concentration against a concentration gradient

 Requires energy from respiration, in the form of ATP (adenosine triphospate)

 Rate of active transport depends on the availability of energy

 More energy, higher rate of active transport

 Active transport is important because it allows cells to obtain nutrients that are in low concentrations outside the cell

Chapter 4 Biological Molecules

 Provides energy for vital activities

 Food provides raw material to make new protoplasm; needed for growth and repair of worn out tissues

 Keeps organism healthy Water

 Solvent for chemical reactions

 Water is needed for many chemical reactions taking placing in living things

 Key component in tissues

 Controlling body temperature

 Via perspiration

 Medium for transporting dissolved substances

 E.g. digested food products and waste products Carbohydrates

 Carbohydrates are organic molecules made up of the elements carbon,

hydrogen and oxygen. Hydrogen and oxygen are present in the ratio 2:1

 Made up of primary units called monosaccharides (simple sugars)  Cannot be further digested into simpler molecules

 E.g. glucose, fructose, galactose. Same formula C6H12O6, but arranged

differently within the molecule

 2 monosaccharides combine chemically to form disaccharides, which are complex sugars

 E.g. maltose, sucrose, lactose. Same formula of C12H22O11, but arranged

differently within the molecule

 Multiple monosaccharides combine chemically to form polysaccharides, which are complex macromolecules

 E.g. starch, glycogen, cellulose

 Condensation reaction is a chemical reaction in which 2 simple molecules are joined together to form a larger molecule with the removal of 1 molecule of water

 Glucose + Glucose Maltose + water

 Hydrolysis or hydrolytic reaction is a reaction in which a water molecules is needed to break up a complex molecule into a smaller one

 Maltose + water Glucose + Glucose ` Polysaccharid e Disaccharide Monosacchari de Condensati on reaction Maltase Hydrolytic

Test for starch

Procedure Results Conclusion

Add a few drops of iodine solution into sample

Iodine remains yellowish-brown

Starch is absent Iodine turns dark blue Starch is present Test for reducing sugar

Procedure Results Conclusion

Add an equal volume of Benedict’s solution to the sample in a test tube. Place test tube into hot water bath for a few minutes

Solution remains blue Reducing sugars are absent Green/orange precipitate

forms

Low concentration of reducing sugars present

Brick red precipitate forms High concentration of reducing sugars present  Just remember color of rainbow. Brick red is high conc., blue is low

 Glycogen and starch are stores of glucose  Plants store glucose as starch

 Animals store glucose as glycogen

 Glycogen and starch are suitable storage materials because

 They are insoluble in water, thus does not change the water potential in cells  They are large molecules which are unable to diffuse through cell membranes, so

they will not be lost from cell

 They can be easily hydrolysed to glucose when needed

 Their molecules have compact shape so they occupy less space than all the individual glucose molecules that make up a starch or glycogen molecule Hydrolysis of starch

Part of a starch molecule amylase

maltase

Glucose molecules

Functions of carbohydrates

 Substrate for respiration, provide energy for all activities  Form supporting structures (e.g. cell walls in plants)  Formation of nucleic acid (DNA)

 Synthesise lubricants (mucus)

 Converted into other organic compounds such as amino acids and fats Fats

 Fats are organic molecules made up of the elements carbon, hydrogen,

oxygen. Unlike carbohydrates, fats contain much less oxygen in proportion to hydrogen

 Fats are made up of 1 molecule glycerol and 3 molecules of fatty acids  Serve as storage of energy and heat insulation

 Used to synthesise the lipid bilayer component of cell membranes

 Fat + water Glycerol + fatty acid  Sources of fats

 Butter  Cheese  Nuts Test for fats

Procedure Results Conclusion

Add an equal volume of ethanol to the sample in a test tube. Mix thoroughly and add an excess of water

Contents of test tube remain clear

Fats are absent A cloudy white emulsion

formed

Fats are present

Proteins

 Proteins are organic molecules made up of elements carbon, hydrogen,

oxygen and nitrogen. Another element, sulfur, may also be present

 Made up of primary units called amino acids which have (-NH2), a (-COOH), an R

group and a hydrogen atom attached to a central carbon atom  Many amino acids are linked by peptide bonds to form polypeptides  Polypeptides are further modified to form proteins

` + 3H2O Fat molecule 3 fatty acid + glycerol lipase lipas Acid group Amino NH 2 COOH R C

Test for proteins

Procedure Results Conclusion

Add an equal volume of NaOH solution to the sample in a test tube. Add a few drops of 1% CuSO4

solution. Shake and mix well

Solution remains blue Proteins are absent Solution turns violet Proteins are present

 Proteins are found in

 Milk, seafood, meat such as chicken

 Plants foods such as soya beans, nuts, grains  Functions of proteins

 Synthesis of new protoplasm, for growth and repair of worn-out body cells  Synthesis of enzymes and some hormones

Chapter 5 Enzyme

 Enzymes are biological catalysts, which speed up the rate of

chemical reactions without themselves being chemically changed at the end of the reaction

 Since enzymes are not consumed by the reaction they catalyse, they can continue to catalyse more reactions after a reaction is complete

 Enzymes are protein in nature

 Work by lowering the activation energy of reactions they catalyse

 Contain active sites which are the reactive portions of the enzyme and act on specific substrates

 Enzymes can catalyse reversible reactions

o From complex molecules to simpler molecules and vice versa

 Almost all reactions are catalysed by enzymes

 Without enzymes, reactions in the body will be too slow to sustain life

 Enzymes are classified as

o Carbohydrases digest carbohydrates o Proteases that digest proteins

o Lipase that digest lipids (fats) Characteristics of enzymes

 Enzymes speed up chemical reactions

o Enzymes speed up the rate of chemical reactions that occur in the cell by lowering the activation energy needed to start a reaction

 Enzymes are required in minute amounts

o Because they remain unchanged at the end of the reaction

o Same enzyme can be used over and over again to catalyse a large amount of chemical reactions

 Enzymes are specific in action

o Highly specific in nature. E.g. amylase on acts on starch, not proteins or fats. o Specific due to its 3-D shape. ‘Lock and key’ hypothesis explains how the

shape of an enzyme affects the way it functions Energy

1. Activation energy with enzyme

2. Activation energy without enzyme

3 2 1

 Enzymes catalyse reversible reactions o E.g. CO2 + H2O ⇌ H2CO3

‘Lock-and-key’ hypothesis

 Substances which substrates act on are called ‘substrates’

 Active sites are depressions on the surface of an enzyme molecule into which the substrate molecule can fit – like a lock-and-key (Enzyme is lock, substrate is key)

o Enzyme has specific 3-D shape, and a specific active site

o Only a specific substrate which is complementary to the active site can fit into the enzyme. This results in the formation of an enzyme-substrate complex

o While substrate is attached to the active site, chemical reactions occur. Substrate is converted into products and later leaves the active site. Enzyme remains

unchanged  General equation is

E + S ⇌ ES ⇌ E + P

Where E = enzyme, s = substrate(s), P = product(s) Factors affecting enzymes

 Temperature

o Every enzyme has an optimum temperature at which it is most active. (Usually 40-45o_C)

o Enzymes are inactive at low temperatures. The kinetic energy is low, hence chances of substrate molecule colliding with enzyme is low

o As temperature increase, frequency of collisions increases, resulting in higher rate of reaction

o Enzymes become denatured at very high temperatures, resulting in little or no catalysis, hence rate of reaction decreases

Denaturation is the change of 3D structure of an enzyme or any other soluble proteins, caused by heat or chemicals such as acids or alkalis

 Denaturation results in loss or alteration of the enzyme’s active site. Substrate no longer fits into enzyme active site and no reaction will occur

 pH

o Each enzyme can only operate within a narrow range of pH

 E.g. pepsin in stomach can only work in acidic environment

o Beyond the optimum pH range, enzymes become denatured, resulting in little or no catalysis

o Highest rate of activity of an enzyme is at its optimum pH

` Carbonic anhydrase Rate of enzyme activity temperature Optimum temperature Rate of enzyme activity Optimum pH

Chapter 6 Nutrition in Humans

Nutrition is the process by which organisms obtain food and energy for growth, repair and maintenance of the body

Alimentary canal

 Consists of mouth, oesophagus, stomach, duodenum, small intestine (ileum, jejunum, duodenum), large intestine (colon) and anus

 Includes salivary gland, pancreas, gall bladder and liver as accessory organs

 Breaks down food from large portions into smaller soluble substances that can be carried in the bloodstream

 Digestion : Process of breaking down food

 Assimilation : Process of making new molecules from simple substances absorbed by the body

o Liver plays a major role in the assembly of biological molecules using substances absorbed via alimentary canal

 Egestion : Process of removing waste products

anus Rectu m colon ileum jejunum duodenu m epiglottis oesophagu s pancreas Bile duct Pyloric sphincter Gall stomach pancreas toungue Salivary gland Mouth cavity

Mouth

 Breaks up food by chewing to increase surface area to volume ratio for faster rate of digestion

 Saliva lubricates food particles to move through oesophagus  Tongue mixes food with saliva and rolls food into a bolus  Salivary glands produce salivary amylase

 Amylase turns starch into maltose Oesophagus

 Food is pushed through oesophagus by rhythmic contractions along its length

 Peristalsis is the rhythmic, wave-like contractions in the wall of the alimentary canal  Oesophagus has 2 layers of muscles

o Longitudinal muscles (outer layer) o Circular muscles (inner layer)

 Longitudinal and circular muscles are antagonistic

o When circular muscles contract, longitudinal muscles relax. Oesophagus constricts, becoming narrower and longer

o When longitudinal muscles contract, circular muscles relax. Oesophagus dilates, becoming wider

Stomach

Circular muscles Longitudinal muscles

Circular muscles relax Longitudinal muscles contract

Circular muscles contract

 Distensible muscular bag which can hold food for a long period of time to allow digestion to take place

 Strong muscles contract rhythmically to churn and break down food

 Secretes high concentration of HCl(aq) acid which kills microorganisms that enter the digestive system

 Also secretes pepsin which are activated and work optimally at low pH

 Secretes mucus, which lines the inner walls of the stomach and protects it from acid and digestive juices

 Pyloric sphincter opens periodically to allow food into the duodenum  Partially digested food that leaves stomach is called chyme

Small intestine

 Consists of duodenum, jejunum and ileum o Duodenum

 Connects stomach to small intestine

 Entry of food controlled by pyloric sphincter

 Site of entry of pancreatic juice and bile from bile duct

 Alkaline environment neutralises acid from stomach and denatures stomach enzymes, preventing damage to duodenum wall

 Bulk of digestion takes place in small intestine (ileum and jejunum)

 Secretes intestinal juice which contains digestive enzymes such as lipase and maltase  Pancreatic and intestinal enzymes work optimally in alkaline pH

 Most food substances are fully digested into simple substances and absorbed into the bloodstream

 Intestinal wall is highly folded with villi and microvilli to increase surface area to volume ratio for more efficient absorption

 Well supplied by blood and lymphatic capillaries to transport away absorbed substances Intestinal villi (singular villi)

 On the surface of the small intestinal wall, there is a high density of finger-like projections called villi

 Epithelial cells on each villus also have projections that are called microvilli

 Villi and microvilli greatly increase surface area to volume ratio for more efficient absorption of digested food substances

 Each villus has a dense network of blood capillaries and a lacteal

 Blood capillaries carry glucose, amino acids and minerals from the small intestine  Lacteals carry fatty acids, glycerol and fat-soluble vitamins from the small intestine  Blood capillaries from the villi of the intestine eventually combine and form the hepatic

portal vein

 Epithelium only one cell thick Large intestine

 Receives undigested food from the small intestine  No digestion takes place in the large intestine

 Prevents excessive loss of water and mineral salts through the faeces by reabsorbing them  Leads to rectum where faeces are expelled through anus

Part Description

Hepatic portal vein  Connects capillaries from small intestine to the liver

 Carries blood rich in absorbed glucose, amino acids and minerals for processing and storage in the liver

 Harmful microorganisms and toxins might cross the intestinal walls to the bloodstream but are eliminated when they reach the liver  Blood that leaves liver has fairly constant concentration of glucose

despite large fluctuations in the hepatic portal vein, especially after a starchy meal

Pancreas  Secretes pancreatic juice containing digestive enzymes such as trypsin, amylase and lipase

 Pancreatic juice is released into the duodenum via bile duct  Secretes hormones such as insulin and glucagon which regulate

blood glucose levels

Gall bladder  Bile is stored temporarily in the gall bladder

 When gall bladder contracts, bile flows into duodenum via bile duct Liver  Receives nutrient-rich blood from the small intestine via hepatic

portal vein

 Produces bile which is necessary to emulsify fats

o Bile is stored temporarily in gall bladder and released into duodenum

 Regulates blood glucose concentration

o Too much glucose makes liver secrete insulin, converting glucose into glycogen for storage

o Too little glucose causes liver to secrete glucagon, converting glycogen into glucose

 Iron storage

o Breaks down haemoglobin from worn-out RBC and stores the iron that is released

 Protein synthesis

o E.g. prothrombin and fibrinogen  Deamination of amino acids

o Deamination is the process by which amino groups are removed from amino acids and converted into urea  Detoxification

o Converting harmful substances into harmless substances

Alcohol

 Harmful to digestive system

o Alcohol stimulates acid secretion in stomach. Excess stomach acid increases the risk of gastric ulcers

Hepatic portal vein Hepatic

vein

Smalll intestine

o Prolonged alcohol abuse leads to cirrhosis of liver – liver cells get destroyed and replaced with fibrous tissue, making liver function less efficiently

 Harmful effects on the nervous system

o Depressant. Slows down some brain functions. Varies from person to person o Reduced self-control

o Effect on reaction time. Slowed reaction time, poor vision, slurred speech, slower reflex actions

Enzyme Produced by Substrate Products

Salivary amylase Mouth Starch Maltose

Pepsin Stomach Proteins Polypeptides

Pancreatic amylase Pancreas Starch Maltose

Pancreatic lipase Pancreas Lipids Glycerol and fatty

acids

Trypsin Pancreas Proteins Polypeptides

Intestinal lipase Small intestine Lipids Glycerol and fatty

acids

Maltase Small intestine Maltose glucose

Peptidase Small intestine Polypeptides Amino acids

Big fat droplets are broken up into smaller fat droplets by the process of emulsification, which increases the surface area to volume ratio of the fats, speeding up their digestion by lipase

Chapter 7 Nutrition in plants

Photosynthesis is the process in which light energy absorbed by chlorophyll is transformed into chemical energy. The chemical energy is used to synthesise

carbohydrates from water and carbon dioxide. Water and carbon dioxide is released during the process

Conditions for photosynthesis  Sunlight

 Carbon dioxide  Chlorophyll

Stages of photosynthesis

 There are 2 stages for photosynthesis: Light dependent stage and Light independent stage

1. Light dependent stage

o Light energy is absorbed by chlorophyll and then converted into chemical energy Light energy Chemical energy

o Light energy is used to split H2O molecules into hydrogen and oxygen molecules in

the process called photolysis 2. Light independent stage

o Hydrogen produced in photolysis is used to reduce carbon dioxide into

carbohydrates such as glucose. Energy required from this process is taken from the light dependent stage

o Enzymes play a part in both light dependent and light independent stages Overall equation for photosynthesis

 6 CO2 + 12 H2O C6H12O6 + 6 O2 + 6 H20

 6 CO2 + 6 H2O C6H12O6 + 6 O2 (simplified equation)

 Carbon dioxide + water  glucose + oxygen Limiting factors for photosynthesis

 Light intensity

 Concentration of CO2

 Temperature

O – A : Light intensity/CO2 concentration is the limiting factor

chloroph yll Light energy Chlorophyl CO2 concentration B A O Rate of B A O Light intensity Rate of

A – B : Light intensity/CO2 concentration is no longer the limiting factor, because other factors are

limiting the rate of photosynthesis

 At low temperature, rate of photosynthesis is low

 As temperature increase, rate of photosynthesis increase

 At high temperature, rate of photosynthesis decreases rapidly due to denaturation of enzymes and proteins involved in reactions

Fates of glucose after photosynthesis 1. Used immediately

 For cellular respiration to provide energy for cellular activities

2. a) In daylight, rate of photosynthesis is high, amount of glucose produced is faster than amount of glucose used. Excess glucose is converted into starch

b)In darkness, photosynthesis stops. Starch converts back into glucose 3. Converted into sucrose

 Transported to other parts of plant or to storage organs such as seeds, stem tubers, root tubers via phloem

 Converted into starch or other forms of storage compounds at storage organs, depending on plant

 Might be converted back into glucose

4. Reacts with nitrates and other mineral salts absorbed in soil  To form amino acids in leaves

i. Used to form proteins for synthesis of new protoplasm in leaves

ii. Excess is transported to other parts of plants for synthesis of new protoplasm or for storage as proteins

 Forms fats

i. For storage

ii. Used in cellular respiration iii. For synthesis of new protoplasm Photosynthesis is important because:

 Makes chemical energy available to animals and other organisms  Removes CO2 and provides O2

 Energy is stored as fossil fuels through photosynthesis

Temperature Rate of

Internal structure of lamina

Upper epidermis  One cell thick

 Covered by a waterproof waxy layer called the cuticle which prevents water loss Mesophyll layer

 Consists of 2 layers : Palisade mesophyll and Spongy mesophyll o Palisade mesophyll

 Consists of one or two layers of closely packed enlongated cynlindrical cells  Higher concentration of chloroplasts than in spongy mesophyll as it is more

exposed to sunlight o Spongy mesophyll

 Cells are irregular in shape  Packed loosely

 Numerous large intercellular air spaces among the cells allows for diffusion of CO2 and O2 within the leaf

cuticle Lower epidermal layer Spongy mesophyll layer phloem xylem Palisade mesophyll layer Upper epidermal layer Stomatal pore

 Lower concentration of chloroplasts than palisade mesophyll  Cells covered with a thin film of moisture

 Contains the transport tissues, xylem and phloem. These are grouped to form vascular bundles

Lower epidermis

 Like the upper epidermis, one-cell thick and covered by an outer layer of cuticle which reduces water loss through the epidermal cell

Stomata (singular : stoma)

 Lower epidermis contains numerous stomata  Regulates exchange of gases

 Each stoma surrounded by 2 guard cells which control opening and closing of stoma  Guard cell contain chlorophyll and can photosynthesise, unlike the rest of the epidermal

layer

Adaptations of leaf for photosynthesis

Adaptation Function

Petiole (leaf stalk) Holds leaf in position to absorb maximum light energy

Thin broad lamina Thin lamina provides short diffusion distance for gases and enable light to reach all

mesophyll cells

Broad lamina provides large surface area for max absorption of light

Waxy cuticle on upper and lower epidermis layer

Reduces water loss through evaporation from the leaf

Transparent to allow light to enter leaf Stomata present in epidermal layer Open in presence of light, allowing CO2 to

diffuse in and O2 to diffuse out of the leaf

Chloroplasts containing chlorophyll found in all mesophyll cells

Chlorophyll absorbs and transforms light energy to chemical energy used in manufacturing of sugars

More chloroplasts in upper palisade tissue More light energy can be absorbed near the leaf surface

Interconnecting system of air spaces in spongy mesophyll

Allows rapid diffusion of CO2 and O2 in and out

of mesophyll cells Veins containing xylem and phloem situated

close to mesophyll cells

Xylem transports water and mineral salts to mesophyll cells

Phloem transports sugars away from leaf Vascular bundle

 Consists of xylem and phloem

o Xylem carries water and mineral salts from the roots to the leaves

o Phloem carries sucrose manufactured from the leaves to the other parts of the plants

CO2 enters leaf through stomata

1. In daylight, when photosynthesis occurs, the CO2 ion the leaf is quickly used up

a. CO2 concentration in leaf becomes lower than atmosphere

b. CO2 diffuses from surrounding air through stomata into the air spaces of the leaf

2. Surface of mesophyll cell surrounded by a thin film of water to allow CO2 to dissolve in

it

3. Dissolved CO2 diffuses into the cells

Xylem transports water and mineral salts to the leaf

1. Xylem transports water and dissolved mineral salts to the leaf from the roots (Chpt 9) 2. Once out of veins, water and mineral salts move from cell to cell right through the

mesophyll of the leaf 4.

phloem Xylem

Chapter 8 Transport in humans

c vein Hepatic _artery

Deoxygena

ted blood _Oxygenated

blood Aorta Pulmonary vein Heart Vena Cava Pulmonary artery

: represents flow of blood Blood

 Contains red blood cells (RBC), white blood cells (WBC), and platelets suspended in plasma  Transports nutrients, dissolved gases and waste products around the whole body

 Protective function against infections by immune system and prevents blood loss by clotting

RBC (Erythrocytes)

 Produced by bone marrow  Most abundant cell type in blood

 Contains haemoglobin, which combines reversibly with oxygen. This enables RBC to transport oxygen from the lungs to the rest of the body

 Contains enzymes which catalyse the rate at which CO2 dissolves in plasma

 Flexible enough to squeeze through lumen of narrow capillaries

 No cell nucleus, which allows cell to carry more haemoglobin and transport oxygen more efficiently

 Biconcave in shape, increasing surface area to volume ratio to absorb and release oxygen at a faster rate

WBC (Leucocyte)

 Produced by bone marrow and lymph gland  Takes up 1% of total vol. of blood

 Clolorless and does not contain haemoglobin  Irregular in shape and contains a nucleus

 Can move, change shape and squeeze through thin capillary walls  2 kinds of WBC

o Lymphocytes

 Large, rounded nucleus  Nearly round in shape

 Produces antibodies that help deactivate toxins and harmful microorganisms o Phagocytes

 Has a lobed nucleus and irregular in shape

 Break down and remove foreign pathogens by engulfing them and ingesting them in a process called phagocytosis

Platelets (Thrombocytes)

 Fragments of cytoplasm from bone marrow cells  Not true cells

Biconcave surface nucleus granule s Lobed nucleu s

 Damaged platelets release an enzyme called thrombokinase which intiates the clotting process

Plasma

 Pale, yellowish liquid, consisting of 90% water and complex mixture of various dissolved substances such as fibrinogen, prothrombin and antibodies

 Functions as a transport medium

 Contain dissolved mineral salts such as chlorides, sulfates and phosphates of calcium, sodium, potassium. All these occur as ions in plasma

 Contains food substances such as glucose, amino acids, fats, vitamins  Contains excretory products such as urea, uric acid, creatinine

 Contains hormones such as insulin Blood groups

 Surface of RBC contain special proteins called antigens  Blood plasma contains antibodies

 Natural antibodies will not react with your own antigens, but may react with others, causing clumping of blood (agglutination)

 People can be classified into blood groups according to the antibodies and antigens present

 The 4 blood groups are A, B, AB, O. Named after antigens present

Blood group A B AB O

Antigen present A B A and B No antigens

Antibody present b a No antibodies a and b

A antigen reacts with a antibody, causing agglutination B antigen reacts with b antibody, causing agglutination Recipient Donor O A B AB O - + + + A - - + + B - + - + AB - - - -+ : agglutination - : no agglutination

O is a universal donor, while AB is a universal recipient. Functions of blood

 Transport function

Substances transported Carried from To

Digested food

- Glucose, amino acids, mineral salts, fats, vitamins

Intestines Other parts of the body

Excess mineral salts transported to kidney for excretion

Excretory products –

Nitrogenous wastes : Urea, uric acid, creatinine

All parts of the body

Carbon dioxide : carried as hydrogen carbonate ions (HCO3- in plasma)

To lungs, where HCO3- is

converted to CO2 to be

expelled

Hormones Glands Target organs

Heat Respiring body tissues (E.g.

muscles)

All parts of the body to maintain a uniform body temperature

Oxygen (transported by haemoglobin in RBC)

Lungs All parts of the body for

cellular respiration How oxygen is transported to the cells of the body

 Haemoglobin in RBC binds reversibly to form oxyhaemoglobin Protective functions of the blood:

 Blood clotting  Phagocytosis

 Antibody production Clotting/coagulation of blood

Phagocytosis is the process of engulfing or ingesting foreign particles, such as bacteria, by the WBC

Tissue rejection is caused by the patient’s lymphocyte responding to the transplant by producing antibodies to destroy the transplant

Prevention of tissue rejection –  Immunosuppressive drugs

o Inhibits the responses of the recipient’s immune system

o However, the recipient would have lower resistance to many kinds of infection o Recipient has to continue taking the drugs for life

Circulatory system  Heart

o A muscular pump

o When relaxing, heart fills up with blood o When contracting, heart forces out blood o Blood circulates around the whole body  Arteries

o Carry blood away from the heart  Arterioles

o Arteries branch again to form arterioles  Capillaries

o Arterioles branch out to form capillaries

Calcium + thrombokinase (thrombokinase produced by damaged tissue and blood platelets) (Inactive) _Thrombin (active) (insoluble) Fibrin threads thrombin (soluble) Fibrinogen

o Microscopic blood vessels made up of a single layer of flattened cells called endothelium

o Endothelium is partially permeable. Enables substances to diffuse through quickly o Capillaries branch repeatedly, forming a large surface area for exchange of

substances between blood and tissue cells  Venules

o Capillaries unite to form venules  Veins

o Venules unite to form veins o Carries blood back to the heart

Arteries Veins Capillaries

Structure Thick elastic muscular walls help to

withstand high blood pressure exerted by the heart  Elasticity helps artery wall to stretch and recoil. Helps to push blood in spurts along the artery, giving rise to a pulse Thinner elastic muscular layer than arteries because blood moves more smoothly in veins, less pressure needed to withstand

One-cell thick walls, no muscular/elastic tissue allows diffusion of substances

between blood and tissue fluid

Small lumen relative to diameter

Large lumen relative to diameter

Large lumen relative to its diameter Semi-lunar valves absent Semi-lunar valves present to prevent backflow of blood Semi-lunar valves absent

Function Carry blood away

from the heart

Carry blood towards the heart

Links arteries and veins Carry oxygenated blood (except pulmonary arteries) Carry deoxygenated blood (except pulmonary vein)

Blood changes from oxygenated in arterioles to deoxygenated at venule

Flow Blood under high

pressure

Blood under low pressure

Blood pressure reduced as blood flows from arteriole to venule end

Blood moves in pulses, reflecting the rhythmic pumping action of the heart

Blood flows rapidly Blood flows slowly Blood flows slowly Transfer of materials between capillaries and tissue fluids

1. When blood enters capillaries from arteries, it is at relatively high pressure

2. Some blood plasma, excluding blood plasma proteins, is forced out of the capillary into the tissue surrounding it

3. Fluid that escapes from capillaries is called tissue fluid, and bathes every cell in that tissue 4. At the end of the capillary, blood pressure is relatively low, fluid enters from the back into

the capillaries where it forms blood plasma

5. This way, freshly supplied tissue fluids containing nutrients and dissolved oxygen constantly replaces tissue fluid containing dissolved wastes

 Mammals go through double circulation, unlike other animals which only go through single circulation

 In double circulation, blood flows through the heart twice in one circuit

 Mammals have a double circulation consisting of pulmonary and systemic circulations o Pulmonary circulation: blood pumped from heart to lungs and back

o Systemic circulation: blood flows from heart to rest of the body and back

 2 upper chambers called atria (singular : atrium)

o Comparatively thin muscular walls since they only need to force blood into ventricles, does not require high pressure

 2 lower larger chambers called ventricles

o Comparatively thick muscular walls, especially the left ventricle, since it has to pump blood to the rest of the body, requiring high pressure

Median septum Semi-lunar valves Aorta Bicuspid valve Tricuspid valve Pulmoary veins Pulmonar y arteries Superior vena cava Inferior vena cava Left atriu Left ventricl e Right ventricl e Right atriu

o Right ventricle has thinner walls than left as it only has to pump blood to the lungs which is close to the heart and requires less pressure, compared to the left ventricle having to pump blood to the rest of the body

 Right and left sides of the heart separated by a muscular wall called median septum, runs down the middle of the heart

o Median septum prevents mixing of deoxygenated blood in the right side with oxygenated blood in its left side

o Mixing of deoxygenated blood with oxygenated blood reduces the amount of oxygen transported to the tissue cells

Cardiac cycle

1. Begins with relaxation of the atria, resulting in blood flowing from the vena cava into the right atrium and from the pulmonary vein into the left atrium

2. Atria contraction increases pressure and forces blood to flow into their respective ventricles

3. Atria relaxation and ventricular contraction cause the closure of the bicuspid and tricuspid valves resulting in the ‘lub’ sound

4. Closure of the bicuspid and tricuspid valves prevent the backflow of blood from the ventricles back to the atria

5. Blood from the right ventricle enters the pulmonary artery 6. Blood from the left ventricle enters the aorta

7. Relaxation of the ventricles causes the closure of the semi-lunar valves, resulting in ‘dub’ sound

8. Closure of semi-lunar valves prevent backflow of blood from the arteries to ventricles when ventricles relax

9. Each cardiac cycle consists of an atrial and ventricular contraction Contraction of ventricles is called ventricular systole

Relaxation of ventricles is called ventricular diastole

1 cardiac cycle

Main arteries of the body:

 The arteries leaving the heart are

o Pulmonary artery from the right ventricle o Aorta from the left ventricle

 From the aortic arch

o Arteries to the head, neck, arm

o Aortic arch curls backwards towards the left side of the heart and continues downwards as the dorsal aorta

 Dorsal aorta distributes blood to regions of the body below the heart. It supplies oxygenated blood through

o Hepatic artery to the liver

o Arteries to the stomach, intestines o Renal arteries, one to each kidney Main veins of the body

 Blood is returned to the heart by

o Pulmonary vein brings blood from the lungs to the left atrium

o Superior vena cava returns blood from the head, neck and arns to the right atrium o Inferior vena cava runs upwards parallel to the dorsal aorta and brings blood to the

right atrium

 Inferior vena cava collects blood from o Renal veins from the kidneys o Hepatic vein from the liver

o Veins from the gut do not open directly into the inferior vena cava. Instead, leads to the hepatic portal vein which leads into liver

Coronary heart disease

 Coronary arteries supply oxygenated blood to the heart muscles  Narrowed lumen of coronary arteries caused by fatty deposits causes

o Atherosclerosis

o This results in an increase of blood pressure

o Such affected arteries develop rough inner surface, increasing the risk of a blood clot trapped in the artery

o A blood clot formed in an artery is called a thrombosis

o When it occurs in the coronary artery, supply of oxygen to heart muscles is reduced or cut off completely

o Without oxygen, heart muscle cells may be damaged, heart attack occurs  Stress, smoking, alcohol and fatty diets increase the risk of developing heart diseases  Leading a smoke-free, healthy lifestyle with regular exercise decreases the risk of

Chapter 9 Transport in plants

Xylem

 Transports water and mineral salts from the roots to the leaves of the plant

 Provides mechanical support to the stem

 Empty lumen with no cross walls or cytoplasm reduces resistance to water flowing through the xylem

 Walls thickened with lignin to prevent collapse of the vessel Phloem

 Transports manufactured food such as sucrose and amino acids from the leaves to the other parts of the plant

 Consists of sieve tube cells and companion cells

o Sieve tube cells only have a thin layer of cytoplasm with perforated cross walls

o Companion cells rich in mitochondria, which provide energy to keep sieve tubes alive for active transport

 Transport of substances occurs by diffusion and active transport

 Holes in sieve plates allow for rapid flow of manufactured food substances through the sieve tubes

phloem xylem

Root hair cells

 Form the epidermal layer of roots

 Have a long and narrow projection which increase surface area to volume ratio for more efficient water absorption

 Central vacuole contains concentrated cell sap, which helps to draw water into the cell from the soil by osmosis

 Have the ability to transport minerals via active transport since they are living cells Translocation

 Transport of manufactured food substances such as sugars and amino acids in plants

 Occurs in phloem vessels which are made up of living cells

 Involves active transport and diffusion Translocation studies

 Using aphids in translocation studies

o Aphids penetrates leaf or stem and feed on phloem

o Anaesthetising the aphid with CO2 and cutting off the body, leaving the

feeding stylet, and examining the liquid that exudes from the cut end of the proboscis shows that it is inserted into the phloem sieve tube, and the liquid is sucrose and amino acids

o This shows that translocation of sugars and amino acids occurs in the phloem

 Using carbon-14 isotopes

o Plant is provided with CO2 containing radioactive carbon, 14C

o When photosynthesis occurs, the sugars formed contain the radioactive carbon. Stem is cut out and exposed onto an X-ray photographic film. o Radioactive substances are present in the phloem, showing that

Entry of water into a plant

 Each root hair cell is a fine tubular outgrowth of an epidermal cell

 Sap in root hair cell is a relatively concentrated solution of sugars and various salts. Water enters root hair cell by osmosis, moving from a region of higher water potential (from soil) to region of lower water potential (root hair cell)

 Water drawn into the root hair cell by osmosis creates a pushing force called root pressure

 Narrow xylem vessels allow water to creep upwards via capillary action

 Water loss through the stomata of leaves creates a suction force to pull water upwards resulting in transpiration pull

1. Water enters the root hair cell by osmosis

2. Because there is a higher water potential in the root hair cell than the neighbouring cells, water moves to it by osmosis

3. This repeats until the water enters the xylem vessels and moves up the plant 3

2 1

Root hair cells absorb ions or mineral salts by active transport

 When the concentration of ions in the soil is lower than in the cell sap, it moves into the cell by active transport, using energy from cellular respiration in the root hair cell

Capillary action

 Water tends to move up very narrow tubes due to interactions between molecules of water and surfaces of the tube

Transpiration pull

 Transpiration is the loss of water vapor from a plant, mainly through the stomata of the leaf

 Spongy mesophyll cells have a thin layer of moisture around them for gases to dissolve and diffuse into the cell

 Evaporation causes water surrounding the cells to be lost as water vapor through the stomata of the leaves when the stomata is opened

 Therefore, loss of water in plant via transpiration is a consequence of gaseous exchange in plants

 Loss of water causes water potential to decrease due to an increase in concentration of dissolved solutes in the cell

 Water then moves from neighbouring cells by osmosis and eventually creates a suction force at the xylem vessels called transpiration pull

 Transpiration is important because it also helps to cool the leaves on the plant Factors affecting rate of transpiration

 Air movement (Wind removes saturated air filled with water vapor) o Increased air movement  increased transpiration rate

 Humidity (Humid air has high concentration of water vapor) o Increased humidity  decreased transpiration rate

 Light intensity (increasing light intensity causes stomata to open) o Increased light intensity  increased transpiration rate

 Temperature (Temperature increase increases rate of evaporation) o Increased temperature  increased transpiration rate

Wilting

 Occurs due to excessive transpiration and insufficient water uptake, resulting in net loss of water from the plant

 Cells of plants become flaccid, resulting in wilting

 Flaccid guard cells close stomata, preventing further water loss from leaves

Chapter 10 Respiration in Humans

 Respiration is the breakdown (oxidation) of food substances with the release of energy in living cells

2 forms of respiration:

 Aerobic respiration

 Anaerobic respiration Aerobic respiration

 Aerobic respiration is the breakdown (or oxidation) of glucose in the presence of oxygen with the release of a large amount of energy. Carbon dioxide and water are released as waste products

 C6H12O6 + 6O2  6CO2 + 6 H2O + Large amount of energy

 Occurs primarily in mitochondria of cells Anaerobic respiration

 Anaerobic respiration is the breakdown of glucose in the absence of oxygen. Anaerobic respiration releases less energy than anaerobic respiration

 Occurs when there is a lack of oxygen/energy provided for muscles by blood to respire, such as vigorous exercise

 C6H12O6  2C3H6O3 + Small amounts of energy

 Glucose  lactic acid + small amount of energy

 Occurs primarily in the cytoplasm of cells

 Accumulation of lactic acid in muscle cells results in muscle pains and fatigue

 Lactic acid is gradually removed from the muscles and transported to the liver o In the liver, some lactic acid is oxidised to release energy, which converts the

Respiratory tract

 Air enters from the nose to the nasal cavity, where nostril hairs help remove large dust particles

 Mucus glands along trachea and bronchi produces mucus which helps trap dust and microorganisms

 Ciliated cells on the inner surface of trachea and bronchi sweep upwards to remove mucus

 Mucus also helps warm and moisten air before entering lungs Alveoli

 Forms a very large exchange surface for gases in the lungs

 Surrounded by a dense capillary network for efficient gaseous exchange

Continuous blood flows from pulmonary To pulmonary vein Alveola r cavity Thin film of moisture

1. Deoxygenated blood from pulmonary arteries enter the lungs and into the capillaries at alveoli

2. Concentration of O2 alveoli is higher than in capillary, thus O2 diffuses into

capillaries and binds to haemoglobin in the RBC to be carried back into the heart 3. At the same time, CO2 concentration in the capillary is higher than alveoli, thus CO2

diffuses out of the capillary into the alveoli to be exhaled

 Alveoli is one-cell thick to minimise distance for diffusion

 Surface of alveoli in contact with air is lined with a layer of moisture to allow gases to dissolve and diffuse across

Breathing

Action Ribs Lungs Diaphragm External

intercostal muscle Internal intercostal muscle Inhaling Moves upwards and outwards Volume increase Contracts and moves downwards Contract Relax Exhaling Moves downwards and inwards Volume decrease Relaxes and moves outwards Relax Contract Removal of CO2

 CO2 is a waste product of cellular respiration

 Carbonic anhydrase is an enzyme found in RBC which catalyses the conversion of CO2 and H2O into H+ and HCO3- ions

 CO2 + H2O ⇌ HCO3- + H+

 These ions are water soluble, carried by blood plasma

 When ions reaches the lungs, ions move back into RBC and are converted back into CO2, which leaves the lungs as a gas during exhalation

HCO3 -HCO3 -CO2 CO2 CO2 + H2O ⇌ H2CO3 ⇌ HCO3- + H+

Smoking and respiratory diseases

Chemicals Properties Effects

Nicotine Addictive

Makes blood clot easily

Increased blood pressure Increase risk of blood clots Increases risk of coronary heart disease

Carbon monoxide Combines with

haemoglobin to form carboxyhaemoglobin Increased rate of fatty deposits on arterial wall

Lowered supply of O2 in the

body

Increased blood pressure Tar and irritants Causes uncontrolled cell

division

Paralyses cilia lining

Increases risk of cancer in lungs Tar accumulates in respiratory airways, obstructing it Diseases caused  Chronic bronchitis

o Epithelium lining on airways inflamed o Excessive mucus secreted

o Cilia and epithelium paralysed. Mucus and dust particles unable to be removed

o Obstructed air passages, making breathing difficult o Persistent coughing to clear air passage

 Emphysema (by violent coughing due to bronchitis)

o Partition wall in alveoli break down due to coughing o Decreased surface area for gaseous exchange o Lungs lose elasticity and become inflamed with air

o Difficulty in breathing – wheezing and severe breathlessness results

 Lung cancer

Chapter 11 Excretion in humans

 Excretion is the process by which metabolic waste products and toxic substances are removed from the body of an organism

The sum of all chemical reactions within the body of an organism is known as catabolism

 Metabolism = Catabolism + Anabolism Human urinary system

 Contains: o Kidneys o Ureters o Urinary bladder o Urethra Ureter

 Narrow tube which connects the kidney to the urinary bladder, and where urine passes through

Urinary bladder

 An elastic muscular bag located in front of the rectum

 Stores urine Urethra

 A duct which urine passes from bladder to outside of body Sphincter muscles

 Located at bottom of bladder, controls urination by contraction and relaxation Kidney

 Cortex

o Contains many malphigian corpuscles

 Malphigian corpuscle is a single nephron o Outer dark red region, granular texture

o Covered by fibrous capsule

 Medulla (pyramids)

o Inner pale red region

o Renal pyramids located in this region

o Striated (Striped) texture containing many tubules

 Renal pyramids

o Conical structure in the medulla o Human kidney has 12-16 pyramids

o Redial stripes on medulla pyramids indicate numerous kidney tubules called nephrons

 Urine is formed in nephrons

 Renal pelvis

o Renal pyramids project into a funnel-like shape called renal pelvis o The enlarged portion of the ureter inside the kidney

Structure of a nephron

 Bowman’s capsule

o Each nephron begins in the cortex as a cup like structure called the Bowman’s capsule

 Proximal convoluted tubule

o Bowman’s capsule leads into a short, convoluted tubule which straightens out as it passes into the medulla

 Loop of Henle

o In the medulla, tubule extends into the renal pyramid and U-turns back into the cortex

o Consists of both the ascending and descending loop of Henle

 Distal convoluted tubule

o The part of the tubule after the loop of henle which is convoluted again

 Collecting duct

o Tubule opens into a collecting duct that runs straight through the medulla to the renal pelvis

Ultrafiltration

 Occurs at the Malphigian corpuscle of each nephron

 Blood enters kidneys by renal artery, branching into many arterioles

 Each afferent arteriole branches into a small ball of capillaries called the glomerulus

 Blood enters glomerulus at high hydrostatic forces (high blood pressure) and most of the blood plasma, excluding proteins and large molecules are filtered out of the capillary

o All blood cells are too large to pass through the basement membrane and are retained in the capillaries. Presence of blood in urine may indicate kidney problems

 The filtrate passes into the Bowman’s capsule and travels in another set of tubules. Filtrate contains water and small molecules (such as glucose and amino acids, mineral salts and nitrogenous waste products). Blood cells, platelets and large molecules such as proteins and fats retained in glomerular capillary

 Filtered blood leaves the glomerulus by an efferent arteriole instead if a vein Reabsorption

 Most of the mineral salts and all of the glucose and amino acids reabsorbed through the walls of the proximal convoluted tubule into the surrounding blood capillaries

o These solutes are reabsorbed by diffusion and active transport. This

reabsorption is highly selective, only the substances required by the body would be reabsorbed

o Water in the filtrate is reabsorbed by osmosis

 Water is reabsorbed at the loop of henle

 At the distal convoluted tubule, some water and mineral salts are reabsorbed

 At the collecting duct, some water is reabsorbed

o Excess water, excess salts and metabolic waste products (e.g. urea, uric acid, creatinine) pass out of the collecting duct into the renal pelvis as a mixture called urine

Osmoregulation is the control of water and solute concentration in the blood to maintain a constant water potential in the body

Amount of water in blood plasma is controlled by anti-diuretic hormone (ADH), produced by hypothalamus, released by the pituitary gland

1. Lower water potential than normal of blood plasma detected by hypothalamus and stimulates pituitary gland to release ADH

2. ADH released into bloodstream causes constriction of blood vessels, increasing blood pressure

3. Reaches the kidney and causes more water to be reabsorbed, hence conserving water and increasing water potential of blood

a. Regulation of water potential is important to prevent dehydration or cells bursting

Kidney failures

 Kidney failure results in the inability of the kidney to remove wastes from the blood or to reabsorb useful substances effectively

 Commonly caused by high blood pressure, damaging the glomerular filtration membranes or caused by diabetes mellitus, which results in excess glucose being filtered and not reabsorbed by the kidney

 Patient is usually treated by dialysis, where a machine takes over the kidney’s job of removing wastes from blood

Drinking more water Drinking less water

Increase Water potential Decrease

Stimulates hypothalamus

Less ADH secreted Pituitary gland secretes More ADH secreted Increased Reabsorption of water Decreased

More Urine Less

Dialysis

 Blood from patient passes through partially permeable tubes inside the dialyser

 Tubes are bathed in dialysis fluid containing salts and glucose in approximately equal concentrations with that of blood

Unwante d material Selective reabsorption Ultrafiltration occurs

 Only urea and unwanted wastes will diffuse across the membrane into the dialysis fluid to be removed

 Blood and dialysis fluid flow in opposite directions to maintain a high concentration gradient for the diffusion of wastes

o This is known as counter-current flow

 Useful substances, proteins and blood cells, remain in the tubes and are pumped back to the patients

Chapter 12 Homeostasis

 Homeostasis is the maintenance of a constant internal body environment, which is essential for survival

 Important parameters include body temperature and blood pH

 Huge fluctuations in these parameters affect enzymatic activities, which affect many of the body’s chemical reactions

 Homeostasis involves

o Thermoregulation – maintenance of a constant body temperature

o Osmoregulation – the maintenance of a constant water potential and pH Corrective mechanism

 Changes in the internal environment of the body are detected by receptors as a stimulus

 Receptors send information regarding the stimulus to a processor which is usually part of the brain

 The processor then sends signals to the effectors which initiate changes in the body to counter the stimulus

 Receptors continue to monitor the internal environment and send information to the processor until the stimulus is removed

 The process of correcting the internal environment through this corrective mechanism is known as negative feedback

Effectors _(Implements corrective

Receptor (Detect

Stimul us

As condition returns to normal, negative feedback is sent to receptor to continue

Regulating blood glucose concentration Response (Condition starts to return to Normal condition Corrective mechanism

Islets of Langerhans secrete insulin  Insulin is transported to liver and

muscle cells

 Insulin increases permeability of cell surface membrane to glucose. Glucose absorbed more quickly  Insulin causes liver and muscles to

convert excess glucose to glycogen, Receptor Islets of Langerhans in pancreas Stimulus Blood glucose concentrati on above

As blood glucose levels decreases, negative feedback is sent to islets of Langerhans to continue

monitoring stimulus until normal

condition is achieved _{Blood glucose}

concentration decreases. Normal condition Stimulus Blood glucose concentration below normal Blood glucose concentration increases As blood glucose levels increases,

negative feedback is sent to islets of Langerhans to continue

monitoring stimulus until normal

condition is achieved _{Corrective mechanism}

Islets of Langerhans secrete glucagon  Glucagon transported to liver

and muscle cells

 Glucagon causes the conversion of stored glycogen to glucose  From liver, glucose enters

bloodstream Receptor

Islets of

Langerhans in pancreas

Regulating blood water potential

Corrective mechanism

 Less ADH released by pituitary gland into bloodstream

 Less ADH transported to kidney  Cells in walls of collecting duct

become less permeable to water  Less water reabsorbed into

bloodstream

 More water excreted  Urine is more diluted  More urine produced Receptor Hypothalamus stimulated Stimulus Water potential increases

As water potential decreases, negative feedback is sent hypothalamus to continue

monitoring stimulus until normal

condition is achieved _{Water potential}

decreases. Normal condition Stimulus Water potential below normal Water potential increases

As water potential increases, negative feedback is sent to hypothalamus to continue

monitoring stimulus until normal

condition is achieved Corrective mechanism

 More ADH secreted by pituitary gland into bloodstream

 More ADH transported to kidneys

 Cells in walls of collecting duct become more permeable to water

 More water reabsorbed into bloodstream

 Less water excreted Receptor

hypothalamus stimulated

Skin

 Functions

o Protect the body from foreign organisms and UV rays from sunlight o Prevent excessive water and heat loss

o Have nerve receptors which contribute to the sense of touch o Production of Vitamin D in the presence of sunlight

Component Organ Function

Receptor Thermoreceptor in skin Detect rise in temperature of skin and sends signals to hypothalamus

Processor Hypothalamus Detects rise in temperature and sends signals to

effectors

Effectors Arterioles in skin Vasodilation occurs to allow more blood to reach the skin and lose more heat Sweat glands Produce sweat which will

take away heat when it evaporates from the skin Thyroid glands Decrease in metabolic rate

of the body to reduce heat production

Hair erector muscles Relax to make hair lay flat to lose more heat

Component Organ Function

Receptor Thermoreceptor in skin Detect fall in temperature of skin and sends signals to hypothalamus

Processor Hypothalamus Detects fall in temperature and sends signals to

effectors

Effectors Arterioles in skin Vasoconstriction occurs to allow more blood to reach the skin and lose more heat Muscles in body Shivering occurs to produce

more heat

Thyroid glands Increase in metabolic rate of the body to increase heat production

Hair erector muscle Contracts to allow hair to stand, trapping air and reducing heat loss (air is a poor conductor of heat)

Chapter 13 Coordination and

response in humans

 Human nervous system consists of

o Central nervous system (CNS) containing the brain and the spinal cord

o Peripheral nervous system (PNS) consisting of nerves connecting the central nervous system and the rest of the body. Function of PNS is to conduct

sensory and motor signals between the CNS and the limbs and organs (receptors and effectors)

 Stimulus is a change in the environment that causes an organism to react. Detected by sensory neurons

 Response is a change in the body as a result of the stimulus. Effectors cells are muscle cells or gland cells which carry out the response to the stimuli

 Receptors collect information from the external and internal environments and send information to the CNS via sensory neurones

 Nerve impulses from the CNS reach the muscles via motor neurons Nervous tissue

 Nerve impulses are transmitted by nerves, which are bundles of neurones wrapped in connective issue

 A neurone is a nerve cell

o Neurones have a cell body, an axon, and a dendron o Cell body contains nucleus and cytoplasm

 3 main types of neurones

o Sensory neurones – transmit nerve impulses from the receptors to the relay neuron in the central nervous system

o Relay neurones – transmit nerve impulses from the sensory neurones to the motor neurones. Found within CNS

o Motor neurones – transmit nerve impulses from relay neurone to effectors muscle cells or gland cells

How impulses are transmitted around the body 1. Stimulus detected by receptors

2. Information is converted into nerve impulses

3. Sensory neurones transmits nerve impulses from sensory neurones to relay neurones in the CNS

4. Brain processes nerve impulses

5. Brain sends other nerve impulses based on the received information from relay neurones to motor neurones

6. Motor neurones sends nerve impulses to effectors 7. Effectors carry out intended action

Structure of neurones Effectors Sensory neurone Relay neuron Motor neurone Central nervous system Nerve impulse receptor

 Dendrons are nerve fibres that transmit nerve impulses towards the cell body

 Dendrites of dendrons receive nerve impulses from other neurones

 Axons are nerve fibres that carry nerve impulses away from the cell body

 Dendrites of axon transmit nerve impulses to other neurones

 Myelin shaft is a layer of fatty substance that shields and insulates the nerve fibre. Myelin sheath is surrounded by a thin membrane known as the neurilemma

 Nodes of Ranvier are regions where the myelin shaft is absent. They speed up transmission by allowing impulses to jump from node to node

 Motor end plates (in motor neurone) is the junction between the dendrite and muscle fibre

Sensory neurone

 Smooth and circular cell body

 Long dendron, short axon

 Transmits impulses from receptor to CNS Motor neurone Nodes of Ranvier Myelin shaft Dendrite of Dendrite of Cell body axon dendron