PURE BIOLOGY FOR SCIENCES BIOLOGY TEXTBOOK
Dunce Name: ______________________ Dummy Index No.: ___________ CHAPTER 1: Cells: The Building Blocks of Life
1.1 CELL STRUCTURE AND ORGANIZATIONS cell – is a unit of life.
protoplasm – a complex jelly-like substance in which endless chemical reactions are carried out. Consisted inside cells, 70 – 90% is water.
Protoplasm exists in 2 forms: - sol (liquid) state
- gel (semi-solid state) state
Scientists can’t make protoplasm, while the components are known... - The exact nature is not fully known
- The environmental conditions is not suitable Protoplasm has 3 parts:
- Nucleus - Cytoplasm - Cell membrane
- consists of a small spherical mass denser than protoplasm, the nucleoplasm. - Embedded inside cytoplasm.
- Control normal cell activities Consists of:
- A long thread structures called chromatin which will condense and become highly coiled structures called chromosomes. It contain heredetary materials and control cell activities.
- Spherical structures called nucleoli to build up proteins.
- A nuclear envelope to seperate nuclear content from surrounding cytoplasm.
- for cell reproduction,
- continuous life of the cell, and - repair worn-out parts.
Without nucleus, i.e. red blood cell, the cell has short lifespan and cannot reproduce. CYTOPLASM
is part of protoplasm surrounding the nucleus.
Role: forms the larger part of the cell and the occurance of life processes.
Organelles in it:
- small spherical/rod-shaped organelles called mitochondria to release energy from food during respiration.
- Adonesine Triphosphate (ATP) to temporarily store energy in small molecules. When needed, it can be broken down for energy.
SPECIAL ORGANELLE IN PLANT
Chloroplast – sites where plant make food by combining carbon dioxide, water and sunlight to make sugar.
Vacuoles – contain cell sap which has dissolved substance like sugars, mineral salts and amino acids, enclosed by special membrane tonoplast.
CELL SURFACE MEMBRANE
is a partially permeable membrane surrounding cytoplasm, controlling substances which enter/leave cell. In plants, it surround vacuoles.
CELLULOSE CELL WALL
Only exist in plant, made of cellulose.
1.2 SPECIALIZED CELLS, TISSUES, ORGANS AND SYSTEMS
Modification of Cell Structure for Specific Functions
The change and development of a new cell produced into new tissues is called differentiation.
EXAMPLES OF SPECIALIZED CELLS
Cell Structure Adaptation to Function
Root hair cell
long and narrow root hair increases surface area : volume ratio for absorption of water mineral and salts.
Red blood cell
contain red pigment - haemoglobin to enable cell transport oxygen from lungs to all parts of body.
circular, biconcave shape increases surface area : volume ratio for higher diffusion rate of oxygen.
The xylem vessel is a narrow, cylindrical tube enclosing a continuous space called lumen. Vessel is dead as there’s no protoplasm. Deposited on the wall is hard substance known as lignin.
transport water and mineral salts from roots to stem and leaves. absence of cross walls allow water move easily through lumen.
lignin strengthens wall and prevent collapse of vessel.
xylem and lignin, bundled together provide mechanical support for plant.
Tissues, Organs and Systems.
Tissue is a group of cells which have common origin and similar structures, enabling them perform a particular function.
Example:epithelium – cell sheets covering internal&external body surfaces
Animals: Muscle tissue, Glandular tissue, Nervous tissue, Bone tissue, etc Plants: Xylem, Pholoem, Cambium, Cork, etc
N/B – tissues that connect different parts of organs together are called complex tissues.
Organ is a structure made up of different tissues working together for specific function.
Example: Stomach – glandular tissue, muscular tissue, connective tissue,
Leaves, Roots, Stems, Flowers, etc.
Organ system is a system made up of several organ working together to perform a special function.
Example: Digestive system, Respiratory system, Nervous system, etc
END OF CHAPTER 1 chmsabee94/5090/06/09 SPECIAL ORGANELLE IN ANIMAL CELL
Centrioles – pair of tiny structures close to nucleus for cell division. Vacuoles – many but small, contain water and food substances
CHAPTER 2:DIFFUSION, OSMOSIS, SURFACE AREA:VOLUME RATIO 2.1 DIFFUSION
Difusion is the net movement of molecules/ions from a region of higher concentration to a region of lower concentration. (or simply: movement of particles down the concentration gradient.)
The movement of particles when there is no net change of movement is known as dynamic equilibrium.
Rule of concentration gradient:
The steeper the concentration gradient for a substance, the faster the rate of diffusion for that substance.
Diffusion and Cells
Substances enter cells mainly from diffusion.
Example:cell membrane is partially permeable,so allowing CO2&O2 to pass amoeba takes in water by diffusion
The particles are passing through permeable membrane from both sides and would be equally blue when the concentrations are equal.
A membrane that allow some substances to pass through but not others is called partially permeable membrane.
The passage of water from a dilute solution to a more concentrated solution across a partially permeable membrane is called osmosis.
Diagrammatic explanation of osmosis:
5% sucrose solution would move to 10% sucrose solution by osmosis through a partially permeable membrane. Water molecules, being smaller, move to limb A and sucrose molecules are too large to pass through. The solution in limb A continues to rise and vice versa for limb B. The solution level stop changing if both have equal concentration of water molecules.
Water potential is a measure of tendency of water to move from one place to another.
Water move from higher water potential to lower water potential ∴ with the relationship of water potential, we can say:
the movement of water molecules from a solution of higher water potential to solution of lower water potential through partially permeable membrane.
Osmosis in Living Organisms
Cell has cell surface membrane works like partially permeable membrane. When put in dilute solution, i.e. 5% sucrose solution, water molecules will enter cell, having lower water potential and sucrose molecules can’t enter due to its larger size.
The U-tube has dilute sucrose solution on arm B and more concentrated sucrose solution in arm A. Arm B has more water molecules. So, we say:
- Solution in arm A is hypertonic to arm B. - Solution in arm B is hypotonic to arm A.
Whilst when we have same solution concentration, i.e. both 5%, we say: - Solutions in arm A and B are isotonic.
From above, we find out that the term:
Hypotonic – the solution has higher water potential than the other one. Hypertonic – the solution has lower water potential than the other one. Isotonic – both the solutions have same water potential.
Cell in a Solution of High Water Potential
Cell sap has lower water potential if placed in a solution of high water potential. Thus, water enter through osmosis.
When water molecules enter in plant/animal cell, so: IN PLANT CELL:
Vacuole size increases, push all contents towards cellulose cell wall, which exerts opposing pressure preventing more water to enter. The cell is turgid.
Turgor: turgidity of cell with water.
Turgor pressure: pressure exerted by water on cell wall.
IN ANIMAL CELL:
Without cell wall to oppose the pressure, the cell will swell and may burst.
Cell in a Solution of Low Water Potential
Cell sap has higher water potential if placed in a solution of low water potential. Water still enter through osmosis, but water move out from cell.
IN PLANT CELL:
Vacuole size decreases, shrinking cytoplasm from cellulose cell wall. The cell is plasmolysed but can return to original state by putting in high water potential solution.
Plasmolysis – shrinkage of cytoplasm from cell wall when immersed in solution of low water potential.
IN ANIMAL CELL:
Cell crenates and dehydrated, thus may die eventually.
Crenation – the process when membrane forms spikes as water is lost and cell shrinks.
Importance of Turgor in Plants
- Maintain shape of soft tissues, i.e. young stems/leaves remain firm due to turgor pressure.
- To move certain plant parts, i.e. change in turgor of guard cell cause opening/closing of stomata.
EXTRA INFO: Why shouldn’t we put too much fertilizers?
Fertilizers make soil more concentrated, causing plant flaccid. To overcome, dilute the soil to prevent wilting and dying.
2.3 ACTIVE TRANSPORT
Is the process in which energy is used to move the particles of a substance from lower concentration region to higher concentration.
- Is occuring when tissue respire releasing energy. - Occur only in living cells as only living cells respire. Examples of active transport:
Absorption of dissolved mineral salts by root hairs
glucose & amino acids absorption by cells in human small intestine 2.4 SURFACE AREA:VOLUME RATIO IN RELATION TO CELLS
CHAPTER 3: ENZYMES 3.1 WHAT ARE ENZYMES?
Enzymes are biological catalyst made of protein which speed up/alter chemical reactions without themselves being changed at the end reaction.
DIGESTION: An Enzyme-Catalysed Process
Enzyme convert complex food molecules into simpler ones to be digested.
Digestion is the process by which large, insoluble food molecules into smaller, soluble food molecules.
3.2 CLASSIFICATION OF ENZYMES
Enzymes can break down in molecules hydrolysis, which is the process of breaking down complex molecule into simpler molecule in which water molecules are needed. Enzyme that break down molecules by hydrolysis are hydrolases.
Carbohydrase – digests carbohydrate Amylase hydrolyse starch
Cellulase hydrolyse cellulose (only plants) Protease, i.e. stomach pepsin – digests protein Lipase, i.e. pancreatic juice steapsin – digests fats
DO YOU KNOW???
- Detergents may contain enzymes to digest organic stains.
- Unripe pineapples and papayas can tenderize meat with their enzymes. But Also Note!!!
- Fruits tenderize meat by covering it on meat before cooking as cooking fire may denature enzyme when heated in high temperatures. (see 4.3)
3.3 CHARACTERISTICS OF ENZYMES
- Enzymes speed up chemical reactions
- Enzymes are required in small(minute) amounts
Enzyme remain unchanged during chemical reaction, so it can be used over and over again on a substrate
- Enzymes are substrate specific
Each enzyme would only react with a praticular substrate, i.e. protease for proteins, lipase for fats. The specificity of enzyme is related to its surface configuration. It’s represented by lock and key specific shown below.
- Temperature affects enzyme activity
Enzymes have optimum working temperature but not always close to that at which they usually function.
From graph, we know:
- Enzymes are least active at low temperatures
- Enzyme reactions speed up as temperature rises. (2x per 10oC) - Enzyme reaches optimum temperature between 40-45 oC at K - Enzyme starts to denature at temperatures beyond K until D
Denaturation is the three-dimensional structural change produced by proteins by heat/pH values which make them coagulate.
Why do Enzymes Denature?
When heated at high temperatures, enzymes undergoes changes in shape, protein become less soluble and coagulates.
Hence, when the three-dimensional structure is altered, enzymes lose their active sites, making them useless now.
- pH affects enzymes
enzyme denatures in extreme changes in acidity/alkalinity. M
In the above graph is rate of reaction of pepsin with pH. • The optimum pH is pH 7
• As solution gets acidic/alkaline, the reaction slows down • At pH 4 or 9, enzyme completely denatures
- Substrate and enzyme concentration affect enzyme reactions
In (i), rate of reaction increases until point X is reached.
• This is because enzyme molecule is saturated, so amount of products formed per time is same.
If an enzyme act on 10 substrates and produce 10 products per second, when there’s 50 enzyme, it’ll react on 500 substrate and make 500 products.
In (ii), the rate of reaction increases as concentration increased, but constant after point Y.
The concentration is now a limiting factor.
Limiting factor is a factor that directly affect the rate at which a process occur if its quantity change.
- Enzymes need coenzymes for activity
Coenzyme is another compound to be bound to enzyme before they catalyse. Mostly they’re non-protein but organic compound.
Examples of coenzymes: vitamin B complex
- Enzymes catalyse reversible reactions A + B C + D
Since most reactions in living cells are reversible, enzymes catalyse reversible reactions too.
The process is usually proceed in forward direction, i.e. A + B to C + D, because the products (C + D) are not allowed to build up but are used up/removed from cell as soon they are formed.
END OF CHAPTER 2 & 3
CHAPTER 4: NUTRITION 4.1 THE NEED FOR FOOD Organisms need food to:
- Provide energy for vital activities of the body
- To synthesize new protoplasm for growth and repair of worn out parts of body and for reproduction
- To maintain good health
* Green plants make use of sun energy for photosynthesis to make food. So, this stored energy in food is potential chemical energy.
Energy is not created/destroyed, but converted from one form to another. With this there’s still a loss of energy even when resting.
Example: muscle cells convert potential chemical energy to kinetic energy to move
4.2 NUTRIENTS IN FOOD
Nutrients are chemical substances in food to nourish the body.
Types of Nutrients:
ORGANIC (Obtained from living organisms): - Carbohydrates - Fats - Proteins - Vitamins - Dietary Fibre INORGANIC: - Water - Mineral Salts Carbohydrates
Carbohydrates are organic compounds made of carbon, hydrogen and oxygen. The ratio of hydrogen to oxygen is same as water, i.e. 2:1
- Comes from mainly plants.
- Are good source of energy for the body.
THREE MAIN GROUPS OF CARBOHYDRATES
Glucose is the simplest carbohyrate sugars. The formula is CnH2mOm, as if n = 6 and m = n, the formula is C6H12O6.
Functions of Carbohydrates - Source of energy
- To form supporting structures, i.e. cellulose cell wall
- To be converted to other organic compounds, i.e. amino acids, fats - For formation of Deoxyribonucleic Acid (DNA)
- To synthesize lubricants, i.e. mucus, made of carbohydrates and proteins to trap dust particles in respiratory system
- Make nectar in flower. The sugary nectar attract pollinating agent Types of sugar
Sugar are sweet crystalline compounds which readily dissolves in solvent.
- Glucose - Fructose - Galactose
Glucose are found in small quantities in all organisms. Fructose is common in animals.
Galactose is a component of milk sugar, lactose. They both rare in organisms like mammals.
Complex sugars are called as the molecule is made of 2 molecules of simple sugars. Also called disaccharides.
- Sucrose - Lactose - Maltose Sucrose
- Is available in sugarcane stems and certain storage roots, i.e. beetroots and carrots.
- Consists of glucose and fructose combined together. - Not found in mammals
C6H12O6(glucose) + C6H12O6(fructose)→C12H22O11(sucrose) + H2O(water)
- Available in milk of all mammals
- Formed by glucose and galactose combined together.
C6H12O6(glucose) + C6H12O6(galactose)→C12H22O11(sucrose) + H2O(water)
- Available in malted cereals and sprouting grains. - Formed during partial digestion of starch
- Consists of two molecules of glucose.
C6H12O6(glucose) + C6H12O6(glucose)→C12H22O11(sucrose) + H2O(water)
These reactions use the process condensation reaction.
Condensation Reaction is a chemical reaction where 2 simple molecules joined together to form bigger molecule with removal of 1 water molecule.
These sugars can return to original compositions by hydrolytic reaction.
Hydrolytic Reaction is when 1 water molecule is added to split up complex molecule into its component units.
ENZYMES TO HYDROLYSE COMPLEX SUGARS: Sucrase – Sucrose + Water → Glucose + Fructose Lactase – Lactose + Water → Glucose + Galactose Maltase – Maltose + Water → Glucose + Glucose
Is made up of many monosaccharides molecules joined together by polymerization, a process of condensing many similar molecules to form a large molecule.
Polysaccharides from condensation of many glucose molecules: - Starch
- Cellulose - Glycogen
Starch is made up of large number of glucose molecules condensed together as bonds. It can broken down by hydrolysing with acid.
Starch is digested with amylase enzyme to form maltose which is digested again with maltase enzyme to form glucose.
FACTS ABOUT STARCH:
- Important source of carbohydrate
- Available in vegetable foods, i.e. cereals, potatoes,etc.
Test for starch:
Iodine Test: Put few drops of iodine onto sample and it will produce blue-black colour.
Glycogen is formed when numerous glucose molecules condense and form highly branches chained of glucose units.
IT IS USED AS:
- Carbohydrate storage in animals and fungi. - In mammals is stored mainly in liver and muscles WHY GLYCOGEN AS STORAGE MATERIAL?
- Insoluble in water, so they don’t change osmotic pressure in cells. - Large molecules; unable to diffuse through cell membrane. - Easy to be hydrolysed to glucose when needed.
Fun Fact: Do You Know Atheletes Take in Bananas Before Sporting?
This is because bananas contain glucose which can be converted to glycogen to be stored and used whenever needed during the sport.
Cellulose is the carbohydrate that forms the greater part of plant cell walls. FEATURE:
- Inactive; very few organisms can digest it.
- Man cannot digest it, but it forms fibre which is important for the functioning of the large intestine.
SIMILARITY AND DIFFERENCE WITH STARCH:
Similar: Consists of glucose linked together to form straight chains. Difference: The way cellulose is linked is different from that of starch.
Fats are organic elements made up of Carbon, Hydrogen and Oxygen, with the proportion of oxygen much less to hydrogen. (C57H110O6)
- It provides energy.
- Used as food stores by animals. Fats can be hydrolysed with lipase enzyme.
C57H110O6 + 3(H2O) → C3H5(OH)3 + 3(C17H35COOH)
(Tristearin) (Water) lipase Glycerol Stearic Acid (Fatty acids) 3 mol 3 mol
FATS AND OILS
fats are solid but oils are liquid at room temperature.
APPLIANCES OF FATS
- As source and storage of energy.
- Insulating material, that is preventing excessive heat loss.
- As a solvent for fat-soluble vitamins and other vital substances like sex hormones and related hormones.
- For protoplasm constituent, especially in protoplasmic membranes.
- butter, cheese, fatty meat, olives, nuts, castor oil seeds, palm oil - saturated fats are fats ocurring in animal bodies.
- unsaturated fats are harmless fats occuring in plants, i.e. vegetable fats. - cholesterol come with saturated fats and can be deposited in arteries which
could cause heart disease.
Test for fats:
Ethanol emulsion – add 2cm3 of ethanol into crushed food substance in a test-tube and shake thoroughly. A temporary emulsion is observed. Add water to turn it into a permanent emulsion.
Are very complex organic substances containing carbon, hydrogen, oxygen and nitrogen. Sulphur and phosphorus are also found.
- always present in protoplasm
- most complex and largest food molecule substances. - Made up of amino acids.
Amino acids linked up to form protein and one water molecule is removed. The bond between 2 amino acids is strong and known as peptides. If there are more than 2 amino acids bonded is known as polypeptides or peptones, and protein molecule is made up with one or more of this chain.
NOTE: The chain of acids in protein is coiled up and weak, so it is easily broken by heat, acids and alkalis, which leads to enzyme denaturation.
Since protein molecule is large, it is broken down to polypeptides and into amino acids to be digested.
PROTEIN DEFICIENCY: When protein is lack (less than 100g), children may suffer deficiency disease called kwashiorkor, which results to make children have swollen abdomens, scaly and cracking skins.
FUNCTIONS OF PROTEINS:
- Synthesizing protolasm for growth & repair of worn-out body cells. - For synthesis of enzymes and some hormones.
- For formation of antibodies to combat diseases. - Source of energy.
Test for Proteins:
BIURET TEST: Add 2 cm3 of egg white and add equal volume of biuret solution. Shake thoroughly and expect a purple colour change.
Vitamins are a group of chemically unrelated organic compounds required in human diet in very small amounts for normal health and development.
fat-soluble vitamins can be stored in fats in the body while water-soluble vitamins cannot be stored, but to be supplied in daily diet.
Vitamins Sources Functions
Vitamin D (fat-soluble)
- fish liver-oils - egg yolk - margarine
- UV rays from sunlight.
Vitamin D is resistant to
heat and oxidation.
- Absorption of calcium and phosphorus from intestines.
- Formation of teeth and bone.
Rickets – poor teeth and soft bones,
causing bowed legs and knock knees.
Osteomalacia – adults; bone softening EXCESS:
Bone demineralization with multiple fractures and calcification of soft tissues. Vitamin C (water-soluble) - citrus fruits - green vegetables - fruit juices Vitamin D is easily destroyed by heat.
- Formation of intercellular substances. - Maintain healthy epitelial tissues.
Scurvy – swollen bleeding gums and
loosening of teeth.
Haemorrhages – internal bleeding in
muscles and skin.
Poor healing and swollen joints. EXCESS:
Excreted by the body
Vitamins Sources Functions
Vitamin B Complex - yeast - liver - bran
Coenzymes in cellular respiration.
Beri-beri, pellagra, pernicious anaemia. Vitamin A - dairy products
- fish liver-oils - green vegetables
- Formation of light sensitive pigment in the retina
- maintain healthy epithelial tissues.
Important because essential constituent of protoplasm. It is also solvent for inorganic salts and other inorganic compounds.
- as medium which various chemical reactions of organism occur
- transporting agent for: digested food substances from intestines to other body parts; excretory products from tissue cells to excretory organs for removal; and hormones from their places of origin to body regions which require them. - a major component of blood, digestive juices and lubricant found in joints. - for hydrolytic reactions during digestion
- reactant in photosynthetic process in green plants
- regulate body temperature by evaporating sweat from skin surface
Minerals are inorganic elements which do not provide energy but are indispensable to readily functions. Examples are:
- calcium - iron
minerals are obtained from plants or animals. Mammals need large quantities of Calcium, Phosphorus, Sodium, Chlorine, Potassium, and Iron.
Sources Requirements Functions
Calcium milk eggs cheese
small fish with bones eaten
cereals soya beans
dark green vegetables
Children: 1 g /day
Adult: lesser, more
during the period pregnancy/lactation
- building bones&teeth - for normal muscle functioning -blood clotting LACK: - Rickets Iron Liver Red meat Egg yolk Bread Flour
Dark green vegetables
Adult: 0.02 g / day Pregnant women: more
For formation of the: - Haemoglobin Red coloured pigment transporting oxygen in the body
Protein in muscle cells that stores oxygen for muscular contraction. - certain enzymes for
Lowering level of the haemoglobin in blood causing anaemia, can be seen by tiredness/ breathelessness.
Dietary Fibre or Roughage
Roughage are indigestable fibrous materials which provides bulk to the intestinal contents and helps peristalsis. Sources are:
- Fruits and vegetables - Bran
- Wholemeal bread - Cereals
Peristalsis – a series of wavelike, muscular movements of walls of digestive tract to enable food mixed with digestive juices.
Constipation – is the absence of proper peristaltic movements resulting in undigested matter in large intestine cannot be moved and too much water absorbed making faeces hard and dry, and removing waste difficult.
To overcome: Take roughage, drink enough water and exercise regularly.
4.3 FOOD VALUES AND DIET A Balanced Diet and Food Values
Balance diet contains right amount of the seven nutrients to meet daily body requirements.
Energy used to carry on vital life processes of body while resting is called the basal metablolism.
The basal metabolic rate depends on these factors: - Climate - Body size - Age - Sex - Health - Occupation Climate
Living in cold country release more heat energy than in tropic country. Thus, basal metabolic rate is higher in cold country.
Bigger build need more energy for basal metabolism than smaller build.
Growing children need more energy for growth than adult. Therefore, children have higher basal metabolic rate.
Men have produce heat more than women due to less fatty tissue. So, men have higher basal metabolic rate.
Thyroid gland produce thyroxine hormone to control metabolic rate. A person with under-active thyroid gland have lower metabolic rate while a person with over-active thyroid gland have higher metabolic rate.
The more active and heavy your work is, the more energy is required, thus the higher basal metabolic rate.
If you need 12 000 kJ of energy daily:
- Eating less than that results in underweight - Eating more than that results in overweight During weight reducing programme:
- Only intake of carbohydrate/fats should be lowered. High protein intake:
- Cause excessive nitrogen in body, to be removed as urea. - Liver and kidney overwork, and may be damaged.
It is advised to:
- Take less fats and cholesterol - Eat more fruits and vegetables - Consume less salts
- Maintain healthy weight
Problems of World Food Supplies
Starvation, Malnutrition, Over-nutrition
Starvation – insufficient energy in mammals or animals.
To meet metabolic rate, body uses stored glycogen and fats. Whe finished, body used proteins from skeletal or heart muscles leading heart weakening
Malnutrition – dietary imbalance due to deficiency or excess nutrients intake over a period of time.
Lack of protein – kwashiorkor. Lack of roughage – constipation. Why starvation and malnutrition?
- Increasing population growth - Unequal food distribution
- Growing cash crops rather foods in developing countries Over-nutrition – intake of more energy than what a person needs.
Results in obesity and coronary heart disease, which forces heart to work harder to pump blood around the body.
Why dietary imbalance?
- Economic constraints, i.e. prefer cheap foods - Poor eating habits – lacking of nutritional knowledge - Unwilling to follow national guidelines
END OF CHAPTER 4
CHAPTER 5: NUTRITION IN MAMMALS 5.1 HOLOZOIC NUTRITION
Nutrition – intake of food ans process to convert food substances into living matter, i.e. cells
Nutrition comprises of:
FEEDING – intake of food into body
DIGESTION – the process whereby large food molecules broken down into soluble and diffusable molecules to be absorbed into cells
ABSORPTION – the process whereby digested taken into cells
ASSIMILATION – the process whereby absorbed food materials are converted into new protoplasm/used to provide energy
Holozoic nutrition – the taking in of ready-made complex organic matter for animals and involving nutritional steps.
5.2 MAMMALIAN DIGESTIVE SYSTEM Consists of gut and glands associated to it Gut consists of:
- Mouth and buccal cavity - Pharynx - Oesophagus - Stomach - Small intestine - Large intestine - Anus Intestines SMALL INTESTINES:
Comprises of duodenum, jejunum and ileum. LARGE INTESTINES:
Made up of caecum, colon and rectum.
Gland is a cell, tissue or organs that secrete chemical substance. Example: salivary gland secrete saliva.
Mouth and Buccal Cavity
Food enters via mouth which leads to buccal cavity. In front of the cavity are moving lower jaws and fixed upper jaws. Food are broken with the teeth. Salivary glands produce saliva into buccal cavity.
The part of the gut from mouth to oesophagus and trachea by way of larynx or voice-box. Larynx has slit-like opening called glottis. To prevent food mass enter wind pipe, a flap-like cartilage epiglottis moves up to cover the trachea.
If food masses or water enter trachea, the person would cough violently to let the food out.
It’s a narrow, muscular tube continuing from pharynx through plorax and diaphragm to stomach. It has 4 layers: - Serous coat
outermost layer, a thin membrane that is moist and slippery to reduce friction between organs.
- Smooth mucsles
muscle layers next to serous coat, outer: longitudinal muscle, inner: circular muscle. Slow and sustained contractions.
- Submucous coat
outer part next to smooth muscles, layer of blood vessels and connective tissues
- Mucous coat
innermost layer, folded extensively and contain gland cells secreting slimy mucus to lubricate food for smooth moving along the gut.
Is the wave-like contractions of the wall of the gut caused by the two layers of smooth muscles.
When circular muscle contracts, longitudinal muscle relaxes, the wall of gut constricts (become narrower and longer) and pushes bolus forward.
When circular muscle relaxes, longitudinal muscle contricts, the wall of gut dilates (wider and shorter) to allow bolus pass through widened lumen.
Is distensible muscular bag with well developed muscular walls. Location: beneath diaphragm to the left side, partly covered by liver. Structure:
- mucous coat of stomach has pits connected to gastric glands secreting gastric juices.
- has muscular valve (pyloric sphincter) which connects to small intestine (valve contracts, entrance closed; when relaxes, entrance open-food pass)
The Small Intestine
Consists of: U-shaped duodenum, jejunum and ileum. Length: 6 metres Function: Wall lining secrete digestive enzymes.
Organs and Glands Associated with the Gut
The Liver and Gall Bladder
Liver: largest gland in body.
Structure: dark-red, made up of five lobes, 3 on the right and 2 on the left. Has 3
blood vessels: hepatic portal vein, hepatic vein, hepatic artery.
Position: below diaphragm, to the right. Upper part touch diaphragm, lower part touch
stomach and small intestine.
Function: secrete bile (alkaline greenish-yellow liquid) containing bile salts and
pigments to help fat digestion. Waste product as faeces.
Gall Bladder: greenish-yellow bag attached to liver which stores bile.
Transporting bile to gall bladder:
Bile duct let bile flow into duodenum when bile duct contracts
Location: lies in the loop of duodenum. Connected to it by pancreatic duct. Function: - produces pancreatic juice having digestive enzymes
- secrete insulin hormone to control blood sugar level and carbohydrate utilization.
The Large Intestine
Structure: shorter but broader than small intestine. Connected to small intestine. At
junction is caecum and appendix which don’t play part in digestion but may cause appendicitis when inflamed. It’s 1.5 metres length.
- Caecum and appendix
- Ascending colon runs upwards at right side of abdominal cavity - Horizontal tranverse colon
- Descending colon runs downwards at left side of abdominal cavity joining rectum.
Function: absorb water and mineral from undigested food matter and remove bacteria
RECTUM: stores faeced temporarily. When contracts, faeces expelled through anus.
5.3 DIGESTION IN HUMANS
In the Mouth
Function: stimulating salivary gland to secrete saliva to mix with food.
- The mucin in saliva soften food
- Chewing increase surface food area, break it into smaller pieces - The enzyme salivary amylase in saliva digest starch to maltose
- Tongue roll the food into small and slippery spherical masses called bolus which later enter oesophagus via pharynx
In the Oesophagus
- Moves bolus down with help of gravity and peristaltic movement
In the Stomach
Food stimulates gastric glands secrete gastric juices and mixes with it by peristalsis. GASTRIC JUICE: dilute hydrochloric acid solution having 2 enzymes, rennin and pepsin. Dilute hydrochloric acid:
- Stops salivary amylase action
- Changes inactive enzymes in gastric juice to be active
- Provide suitable slightly acidic medium for gastric enzyme action - Kill germs and parasites
The enzymes are produced inactively in the form of: - Pepsinogen
They are later converted by acid to be rennin and pepsin.
PEPSIN: Digests proteins to polypeptides/peptones. It’s inactive as it will digest cells
which consist of mainly proteins.
RENNIN: Curdles milk protein by converting soluble milk protein (caseinogen) into
insoluble one (casein) and later digested by pepsin.
* If not converted to casein, it wouldn’t be digested and get to duodenum.
In the Small Intestine
The chyme (liquefied food) will stimulate:
- Intestinal gland to secrete intestinal juice
- Pancreas to secrete pancreatic juice which passes pancreatic duct to duodenum
- Gall bladder to release bile. Bile passes bile duct to duodenum
Note: Bile, Pancreatic juice and Intestinal juice are alkaline to neutralize acidic chyme from stomach and provide alkaline for enzyme action.
The enzymes in intestine:
- pancreatic amylase, pancreatic lipase and trypsinogen(all protease)
Enzymes in intestine:
- enterokinase, erepsin(all peptidase), maltase, sucrase, lactase and intestinal
Carbohydrate digestion in small intestine:
- Food enters mouth. Salivary amylase digest partial starch into maltose. - Boli enter stomach. No carbohydrate digestion occurs.
- Boli enter small intestine. Starch digested to maltose. - Cellulose carbohydrate is not digested.
- End products are simple sugars
Fat digestion in small intestine:
- Bile emulsifies fats so fats are simplified and sufrace area enlarged - Emulsified fats are digested by lipase
- End products are glycerol and fatty acids
Protein digestion in small intestine:
- Protein partially digested in stomach
- In intestine, inactive trypsinogen converted to active trypsin enzyme by intestinal enterokinase.
- Protein further digested in small intestine to polypeptides by trypsin - Polypeptides are digested by intestinal erepsin in intestinal juice - End products are amino acids
Summary of digestion in human gut
Simple sugars, amino acids, fatty acids and glycerol are absorbed by the villi of small intestine especially of the jejunum and ileum.
Adaptations of the Small Intestine for Absorbed Digested Food Products
- Inner walls of small intestines are thrown into numerous transverse folds and furrows.
- Small intestines has numerous finger-like projections called villi to increase surface area for efficient absorption.
- Epithelial cells in villi bear microvilli
- Between villi are small opening of intestinal gland to produce intestinal juice. - Intestinal wall and villi are supplied with blood vessel and lympathic vessel to
carry away food substances.
- Lympathic capillary transport fats away from small intestine - Blood capillary transport sugars and amino acids away
Process of Absorption
Carbohydrate, protein and other substances absorption
- Simple sugars, amino acids, mineral salts and vitamins pass through walls of villi into blood capillaries.
- Blood transports them to other body parts.
- Glycerol diffuse into epithelium (dissolves in water).
- Fatty acids react with bile salts, forming soluble soaps, and diffuse into epithelium.
- In epithelium, the soaps and glycerol combine to form fat globules and absorbed in lympathic capillary.
In the large intestines
- Water and mineral salts absorbed here.
- Undigested/unabsorbed matter are stored temporarily in rectum and egested.
Egestion is removal of undigested matter from the body.
Assimilation – transport and utilization of absorbed food
- The blood capillaries rich of simple sugars from small intestines unite to form larger blood vessel which forms hepatic portal vein to transport sugar to liver.
- In liver, most absorbed sugars are stored as glycogen. Sometimes glucose bypass liver.
Glucose processing in liver and pancreas:
- glucose oxidation during tissue respiration release energy for vital activities of the cell.
- pancreas produces hormone insulin used to convert excess glucose as glycogen.
Glycogen is converted back to glucose in liver when needed for energy.
- are passed through hepatic portal vein with sugars.
Are used for:
- enter cells to be converted to new protoplasm - used for growth and repair of worn-out tissues - formation of enzymes and hormones
- Lymphatic capillaries contain colourless liquid – lymph.
- When fats are absorbed into these capillaries, they mix with lymph to produce milky fluid – chyle.
- Lymphatic capillaries join to form larger lymphatic vessels to discharge chyle into bloodstream and carries fats to all body parts.
But before fats are used:
- They are brought to liver - converted to oxidizable/storable forms. But when there are enough glucose, fats are not oxidized.
Use of fats:
- Build protoplasm in cell membranes.
- Excess stored in adipose tissues which are fat storage and insulating tissues found beneath skin, around heart and kidneys.
The Liver: Functions Associated with Digestion and Assimilation
Production of Bile
Bile - produced by liver to emulsify fats, stored temporarily in gall bladder.
Regulation of Blood Glucose Concentration
Liver keeps amount of glucose in blood constant of 70-90mg/100cm3 blood
After heavy meal:
- Glucose in blood rises, excess glucose converted to glycogen by liver and stored, leaving blood having fair amount of glucose.
When need glucose:
- Glucose in blood drops, glycogen converted back to glucose by liver.
- Glucose in blood drops, brain send impulses to empty stomach and give hunger sensations
After fasting and eating:
- Blood glucose rises, brain send impulses to stomach, hunger stopped
This deposition and mobilization of glycogen are controlled by the hormones
insulin and adrenaline.
Other Important Functions of The Liver
his Information Might be Helpful!
Liver produce plasma proteins such as albumins and globulins from amino acids for blood clotting with fibrinogen.
Worn-out red blood cells are destroyed in spleen and the haemoglobin are brought to liver to break haemoglobin down and store iron that’s released in the process. Bile pigments are produced too.
Harmful substances such as benzoic acid, picric acid, alcohol and chloroform may be absorbed in gut. These are converted to harmless substances by liver – process is detoxication.
Heat can be produced during chemical activities in liver. The heat is distributed by blood to other body parts to regulate body temperature. Heat Production
CHAPTER 6: NUTRITION IN PLANTS 6.1 PHOTOSYNTHESIS
Photosynthesis – the process whereby light energy is absorbed by the chlorophyll and transformed into chemical energy used in synthesis of carbohydrates from water and carbon dioxide and produces oxygen.
Knowledge Required for Doing Photosynthetic Experiments
- Since simplest carbohydrates are sugars, to prove photosynthesis took place,
sugars must first be formed from carbon dioxide.
- Sugars are formed faster than being used up, so it’s changed to starch to prevent excess for storage. (THIS ISN’T PART OF PHOTOSYNTHESIS!) - In darkness, photosynthesis stops, enzymes in leaves changed starch to
sugars and transported to other plant parts.
Conditions Essential for Photosynthesis
- Sunlight - Carbon dioxide - Chlorophyll
- Temperature (for enzyme in chloroplasts) - Water
Photosynthesis occur in 2 stages:
- Light-dependent stage - Light-independent stage
Light energy is absorbed by chlorophyll to: - Convert it into chemical energy.
- Split water molecules into hydrogen and oxygen – photolysis.
means the stage where light is not required for the activity.
- Hydrogen produced reduces carbon dioxide to glucose by using chemical energy provided during light-dependent stage.
Simplified diagram to relate light-dependent and light-independent stage:
- Active energy of light converted and stored as carbohydrate molecule that is glucose.
- 12 water molecules splits up to all 6 oxygen molecules and 24 hydrogen atoms. - The hydrogen reduce 6 carbon dioxide molecules to form a glucose molecule and
6 water molecules.
Combining these steps, we get:
From graph, we know not all wavelength are absorbed. - Only red and blue are most effectively absorbed.
- Green is hardly absorbed, therefore chlorophyll are green as it reflects most green lights.
The higher the wavelength absorption, the higher the photosynthesis rate LIGHT AND PHOTOSYNTHESIS
- Light is absorbed by chlorophyll.
- Light moves in waves, energy is contained in pockets called photons.
- Photon is inversely proportional to light wavelength; the longer wavelength, the less energy per photon.
Sunlight has spectrum of light, which red (longest wavelength) and blue (shortest wavelength) are most effective for photosynthesis
- Carbon dioxide concentration - Light intensity
GRAPH 1 AND 2
- as light intensity increases, photosynthesis rate increases to A and then remain constant. A is limiting factor of light. Beyond that is not
- as temperature increases with same CO2 concentration, the rate doesn’t increase appreciably so temperature isn’t so limiting factor
GRAPH 3 AND 4
- CO2 concentration increased, rate increased. CO2 is limiting factor - at E, limiting factor is temperature as difference is appreciable
The fate of glucose in leaves
First, CO2 and H2O produce glucose in leaf by photosynthesis. It’s used: - By cells during tissue respiration to provide energy.
- To make cellulose cell walls.
- Excess glucose converted to sucrose transported to storage organs to be stored as starch or other forms.
- During day, sugars are formed faster and these are accumulated in leaf to be converted to starch for temporary storage in leaf. At night, photosynthesis stops, leaf enzymes reconvert it to glucose.
- To react with nitrates and other mineral salts brought to the leaf to form amino acids to form proteins which is converted into new protoplasm within the cells. o Excess amino acids are stored as proteins in the leaves or carried to growing
regions of plant to build new protoplasm or stored as proteins. - To reach storage organs & convert to fats – stored within these organs.
Digestion and Utilization of Stored Food in Plants
Stored fats, proteins and starch in storage organs can be digested to soluble and diffusable substances by the enzymes produced by storage organs when needed diastase maltase
Digestion of Stored Food
pepsin and erepsin
2. proteins polypeptides and amino acids
3. fats fatty acids and glycerol
Digested food are carried to all plant parts, especially growing zones.
Utilization of Stored Food
- Sugars and digested fats for energy production. - Amino acids assimilated to form new protoplasm.
The Importance of Photosynthesis
- During photosynthesis, carbohydrates are formed which further forms fats, proteins and other organic compounds which become food to animals directly or indirectly.
- Sunlight energy is converted to chemical enery which is stored within carbohydrates molecules, which is fed to animals and the energy stored is passed to them.
- Coal from trees has energy from sunlight through photosynthesis. When burnt, energy produced is used to cook, machine works, etc.
- Photosynthesis purifies air by removing carbon dioxide andproduce oxygen for animal respiration.
6.2 THE LEAF: NATURE’S FOOD MAKING FACTORY
A green leaf is equipped with lamina, petiole and leaf base for functioning
Holds lamina away from stem so lamina obtain sufficient sunlight and air.
- Has large surface area:volume ratio for maximum sunlight absorption. - Thin expanded lamina- carbon dioxide reach rapidly the inner laef cells.
Vein networks and Vein branches
Carry water and mineral salts to cells in lamina and carry manufactured foods to other parts of the plant.
Main vein that gives off branches and form a network of fine veins.
Internal Structure of the Lamina
The lamina on either side of mid-rib has upper epidermis.
- consists of single layer closely packed cells covered with cuticle outside
- Prevents excessive evapiration of water - Focuses light into mesophyll layers
Lies below upper epidermis. - Main site of photosynthesis
- Has 2 regions – palisade tissue & spongy tissue
Palisade Cells Tissue
Consists of 1 or 2 layers of closely packed, long cylindrical cells with axes at right angles to the epidermis.
- Cells has numerous chloroplasts for maximum sunlight absorption for photosynthesis process.
Chloroplast – oval-shaped structures which contain chlorophyll
Spongy Mesophyll Tissue
Has irregular shaped cells, containing chloroplasts too, which are loosely arranged to provide large intercellular air spaces among them.
Lies below mesophyll, consists of 1 layer of closely packed, covered by outer cuticle layer. Has small openings called stomata, and bounded with 2 guard cells.
Differences between guard cells and epidermal cells:
GUARD CELLS EPIDERMAL CELLS
Bean-shaped in surface view Irregular shape
Contain chloroplasts-photosynthesis Doesn’t contain chloroplasts
Can make sugar Cannot make sugar
Prevent water loss by closing stoma Do not regulate water amount
How guard cells work:
Potassium concentration increases in guard cells and with sugars formed, water potential in guard cell lowers so water from outer cells enter guard cells by osmosis making it turgid. As guard cell have thicker cellulose cell wall on one side of cell, guard cell swollen and curved, pulling stoma open.
During the day
Sugar is used up, water leaves guard cell so it turn flaccid. Stoma closes.
During the night
The entry of carbon dioxide into the leaf
During daylight, photosynthesis occurs, so carbon dioxide in leaf used up. Carbon dioxide concentration in leaf is lower than outside so carbon dioxide from outer enviroment diffuse into air spaces leaf and dissolves in thin film of water which covers mesophyll cells.
The entry of water and mineral salts inro the leaf
Veins in leaf form branches which end among mesophyll cell, containing xylem and
Xylem – brings water and mineral salts to leaf from soil via roots. When out of veins,
these materials diffuse cell to cell throgh leaf mesophyll.
Phloem - transport sugars produced by green leaf from the raw materials to all plant
How Is Leaf Adapted to Photosynthesis?
6.3 MINERAL NUTRITION IN PLANTS Essential elements:
Oxygen non-metallic Calcium metallic
These elements occur in traces of plant and human body.
- Hydrogen and Oxygen are needed for building of carbohydrates which are starting blocks in which all other glands in plants are made. They can be obtained from water that plant take in.
- Carbon Dioxide is needed for photosynthesis. - Water is essential for healthy growth of plant.
END OF CHAPTER 6
CHAPTER 7: TRANSPORT IN ANIMALS
7.1 THE NEED FOR A TRANSPORT SYSTEM To carry substances from one body part to another: Blood System: having the fluid blood
Lymphatic System: having the fluid lymph
STRUCTURE AND COMPOSITION OF BLOOD 55% plasma (fluid part of blood), 45% platelets Plasma
Red blood cells (erythrocytes) BLOOD Blood Cells
White blood cells (leucocytes) Platelets
Pale yellowish in colour
90% water containing various dissolved substances:
- Soluble protein: serum albumin, serum globulin, antibodies
fibrinogen, prothrombin. Fibrinogen & Prothrombin: Clotting of blood;
Antibodies: Fighting diseases
- Dissolved mineral salt: Ions of chloride, bicarbonate (HCO3), NaSOX,
NaPOX, KNOX, KPOX, Calcium. Calcium: blood clot
- Food substances: Glucose, Amino Acids, Fats, Vitamins - Excretory products: urea, uric acid, creatinine
- CO2, present as HCO3 ions - Hormones
Red Blood Cells (Erythrocytes)
Shape: circular, flattened, biconcave disc – centre of cell thinner than edge Characteristics:
- No nucleus
- Diameter less than 0.01 mm
- Can squeeze through capillaries smaller than its diameter - Produced in bone marrow
- Lifespan 3 – 4 months
- When worn out, it’s destroyed in spleen and liver Content of RBC:
HAEMOGLOBIN: a red coloured pigment protein containing iron.
- Lets blood cells transport oxygen from lungs to all body cells
White Blood Cells (Leucocytes):
Shape: Irregular, can change shape to squeeze among blood capillaries and between tissue cell spaces.
Characteristics: - Has nucleus
- Colourless and no haemoglobin - Fewer than RBC (Ratio: 700:1) - Keep body healthy by fighting disease - Lifespan: Few days
Types of WBC: - Lymphocytes
- Produced in lymph glands/lymph nodes
- Has large rounded nucleus, few non-granular cytoplasm - Almost round shaped, rarely move
- Produced in bone marrow
- Ingests foreign particles, e.g bacteria (phagocytosis) - 2 kinds: monocytes – bean-shaped nucleus
polymorphs – many lobed-nucleus, granular cytoplasm
Phagocytes Platelets (Thrombocytes):
- Cytoplasm fragments of bone marrow, for blood clotting. FUNCTIONS OF BLOOD
- Medium to carry various substances from one body part to another - Protects body against disease-carrying organisms (pathogens)
Transport function of blood
Blood transports the following:
- Digested food substances from the intestines to all parts of body
- Excretory products from tissues to respective excretory organs for removal. o Nitrogenous wastes (urea, uric acid, etc) removed by kidneys.
o CO2 in cells enter blood as HCO3 ions in blood plasma. As blood passes lungs, HCO3 ions dissociate to release CO2 into lung cavities by diffusion which then expelled during expiration.
- Hormones from producing glands to requiring body parts.
- Fat produced in respiring body tissues (i.e. muscle, liver) to body parts to maintain stable body temperature.
- Oxygen, combined with haemoglobin from lungs to all body parts.
Oxygen is carried in RBC. Haemoglobin greatly affinates with oxygen.
- As blood passes through lungs, oxygen diffuses from lung cavities into cells. It’ll then combine with haemoglobin, forming a new bright red coloured compound called oxyhaemoglobin.
Oxyhaemoglobin releases oxygen when encountering tissues lacking of it.
- Oxygen released diffuse in solution into tissue cells to give adequate oxygen supply.
Haemoglobin w/o oxygen → purplish red ∴ arteries are seen red, veins are seen bluish.
Carbon Monoxide (CO) Poisoning
CO combines more readily than oxygen with haemoglobin to form bright pink compound carboxyhaemoglobin. The compound does not readily release CO, so they are useless.
Acclimazation to high altitudes
High altitudes → more RBC
- Oxygen concentration low → haemoglobin & RBC must increase to allow more oxygen transported to tissue cells per unit time.
Protective function of blood
- Engulfing and ingesting foreign particles, i.e. bacteria by WBC
- Some phagocytes may die in the process. They mix with dead bacteria forming pus.
The need for phagocytosis:
- One celled organisms, i.e. Amoeba, engulf food and ingest in food vacuole. The digested products are absorbed and assimilated directly in cytoplasm. - Dead cells in humans are phagocytosed to prevent inflammatory reactions by
body’s immune system. - As immunity against bacteria.
Production of antibodies
- Disease causing germs may produce poisonous substance toxin which also induce production of antibodies by the lymphocytes and can be found freely in the plasma.
- Act as antitoxin to neutralize poisonous effects of toxins. - Kill bacteria in blood.
- Agglutinate (clump) bacteria together before phagocytosed. Clotting or coagulation of blood
Blood exposed to air will soon clot to seal the wound. - To prevent excessive loss of blood
- To prevent foreign particles entering the blood stream
Is hereditary disease which impair normal blood-clotting system. Sufferer may die due to excessive bleeding or internal bleeding.
THE CLOTTING PROCESS:
- Blood vessels damaged → damaged tissues & blood platelets release enzyme → thrombokinase
- Prothrombin in blood plasma activated by thrombokinase + calcium ions → thrombin
- Thrombin catalyses fibrinogen (soluble) → fibrin (insoluble threads) - Fibrin threads entangle blood cells, they form clot.
Blood in undamaged blood vessels don’t clot as heparin from liver → anticlotting substance.
- Thrombokinase released → neutralise heparin → clot takes place
- Blood clot → serum (yellowish liquid with same composition of plasma but more anticlotting subtituent) left behind
Organ transplant and tissue rejection
Means: Replacement of damaged/diseased organs/tissue with healthy one
Tissue may be rejected by recipient’s immune system as:
Organ from another person = foreign body. Lymphocytes may destroy it.
Tissue may not be rejected when:
The tissue transplanted is from the same person.
Tissue match (donor’s & recipient’s tissue must be as close as possible, i.e. brothers, sisters, parents)
To prevent tissue rejection:
Usage of immuno-suppressive drugs → inhibit immune system activity Bad: Recepient prone to infections & to continue treatment forever
X-Ray radiation to bone marrow & lymphoid tissue to inhibit blood cells production. Hence, slows down rejection.
7.3 THE CIRCULATORY SYSTEM
Blood Circulation – The transportation of blood carrying various substances from one part part of the body to another by flowing continuously around the body through a closed system of blood vessel.
- Blood is kept flowing by muscular pump of the heart
o Heart relaxes → filled with blood; heart contract → squeeze blood out Large arteries leaving left side of heart – aorta
- Branches to form smaller arteries and branch again to form tinier arteries called arterioles and arterioles divide to form even tinier blood vessels –
Capillaries – microscopic blood vessels found between most tissue cells
- Walls made of single layer of greatly flattened cells – endothelium - Endothelium enables certain substances to diffuse quickly
- Branches repeatedly → more branches → large surface area → exchange of substances between blood and tissue cells
- Before leaving organ/tissue, they unite - form small veins - venules When arterioles branches to capillaries, total cross-section area increases
- Lowers blood pressure of capillaries → slows blood → more time for exchange of substances
- Have thick, muscular and elastic walls withstand pressure when pumped out of the heart (the great arteries near heart is thicker)
- Thick elastic walls to maintain high blood pressure in artery - Wall elasticity permit stretching and recoiling of wall, to push blood - When artery constricts, lumen narrower, less blood flows through - When artery dilates, vice versa
- Have thinner walls as the blood pressure is low. - Less elastic tissues.
- Have internal valves to prevent backflow of blood. The valves are folds of the inner walls, shaped half-moon – semilunar valves
- Movement of blood assisted – skeletal muscle action
o Muscular excercise increases pressure exerted on veins and moves blood along quickly.
7.4 DOUBLE CIRCULATION
This means blood passes the heart twice in one complete circuit. It consists of SYSTEMIC CIRCULATION and PULMONARY CIRCULATION
- In pulmonary circulation, deoxygenated blood is carried to lungs via pulmonary artery and oxygenated blood is returned to heart via pulmonary vein.
- In systemic circulation, oxygenated blood is carried to all body parts from left side of heart via aorta and deoxygenated blood returned to heart via vena cava. The deoxygenated blood undergo pulmonary circulation & again systemic circulation.
Double Circulation is Important Because:
- Oxygenated blood is separated from deoxygenated blood: Median septum in heart ensures complete separation and oxygenated blood flows through left side of heart while deoxygenated blood flows through right side of heart.
- Blood pressure in systemic circulation is kept higher than pulmonary circulation as left ventricle, with thicker wall to withstand high pressure, pumps blood to all body parts under high pressure for faster delivery of oxygenated blood to body cells in systemic circulation while right ventricle, with thinner wall, pumps blood to lungs under low pressure to prevent lung damage.
Right Auricle Left Auricle
Main Blood Vessels of Body Coronary Blood Vessels:
Coronary Arteries – branch from aorta to provide blood for heart muscles.
Coronary Veins – they converge into main vein to transport deoxygenated blood from heart muscle tissues to right atrium
Liver Blood Vessels:
Hepatic Artery – brings blood to liver from heart Hepatic Vein – brings blood from liver to heart
Hepatic Portal Vein – brings blood from gut to liver and breaks up into many capillaries before they converge into hepatic vein. It’s called portal vein as it carries blood from one capillary network to another.
Kidney Blood Vessels:
Renal Artery – brings blood to kidneys from heart Renal Vein – brings blood from kidneys to heart
7.5 OUR HEART, OUR PUMP
The heart is located in thoracic cavity between two lungs. It is protected by sternum and rib cage and surrounded by two-layered membrane called pericardium on which between these two membranes contains pericardial fluid to reduce friction when the heart is beating.
Median septum separates the left side of heart from the right side of heart.
The chambers types are namely atria on the upper chambers having thin wall, and ventricles on the lower chambers, having thick walls. Atria have thin walls as it only have to force blood into ventricles with low force but ventricles need thick walls as it needs pressure force to transport blood to other body parts.
The 4 chambers in heart are:
Right Atrium: Upper chamber of the right side of heart. Blood from other body parts are returned via anterior and posterior vena cavae. When the atrium contracts, blood flows from right atrium into right ventricle through tricuspid valve, consisting of 3 flaps, which opens downwards.
Right Ventricle: Lower chamber of right side of heart. When it contracts, blood pressure forces the flaps to close, preventing backflow of blood into right atrium after receiving blood from it. Blood then leaves the ventricle via pulmonary arch into pulmonary arteries, one to each lung, with backflow of blood prevented by semilunar valves. Left Atrium: Upper chamber of left side of heart. Oxygenated blood returned to heart
via pulmonary veins which opens here. When left atrium contracts, blood enters left ventricle via bicuspid valve, consisting of 2 flaps. Left Ventricle: Lower chamber of left side of heart. When it contracts, flaps close and
blood leaves ventricle via aoric arch under high pressure to all over the body and backflow is prevented by semilunar valves in aortic arch. Chordinae Tendinae attaches the bicupid and tricuspid valves to ventricle walls and prevents blood pressure from forcing the valves to open upwards into atria.
Coronary contraction is termed systole while coronary relaxation is called diastole. The bicuspid and tricuspid valves are atrioventricular valves of a heart.
Systole and diastole make up one heartbeat. An average person average heartbeat is 70 beats per minute (BPM).
CHAPTER 8: TRANSPORT OF MATERIALS IN FLOWERING PLANTS 8.1 FLOWERING PLANT STRUCTURE IN RELATION TO TRANSPORT
TRANSPORT (VASCULAR) TISSUES
Consists of xylem and phloem; for transporting materials in flowering plants
- Conducts water with mineral salts from roots to stems & leaves - Provides mechanical support within the plant
Xylem consists of mainly vessels.
Vessel – long hollow tube fetching from root to leaf.
- have a continuous hollow space (lumen).
- is a dead structure.
- wall strengthened by a deposited substance, lignin, deposited in the form of rings (annular), spirals or pitted.
- lumen without partition to hinder passage of water & mineral salts. - lignified walls prevent collapse of vessel.
Conduct manufactured food from green parts of plant to other parts of plant Consists of: sieve tubes; companion cells
Consists of a row of elongated, thin-walled living cells – sieve tube cells
Cross walls seperating the cells perforated by minute pores – sieve plates
Mature sieve tube – no central vacule & nucleus, but thin cytoplasm layer
Transport of food – through sieve tube cells & sieve plates cytoplasm by diffusion and active transport
Companion cells – to keep the tubes alive & to assist transportation of food
INTERNAL STRUCTURE OF PLANT ORGANS Internal Structure of Dicotyledonous Stem
Phloem & Xylem together – vascular bundles
Vascular bundles arranged around a central region, pith. Xylem & phloem lie along same radius.
Phloem outside xylem, with tissue, cambium in between.
- Cambium cells divide to form new xylem and phloem tissue – thicken stem
Covering layer of cells – epidermis
Epidermal cells protected from evaporation from stem by cuticle. Region between vascular bundles & epidermis – cortex
Cortex & pith – store food substances
Internal Structure of Young Dicotyledonous Root
Xylem & phloem lie on different radii, alternating with each other.
Cortex – storage tissue
Epidermis of root bearing hair – piliferous
Root hair – tubular outgrowth of epidermal cell.
Cuticle absent in piliferous layer
Translocation of Organic Food Substances
Translocation: Transport of food manufactured substances (e.g. sugars, amino acid)
1. Anaesthesize feeding aphid on plant stem and remove the body from its proboscis. A liquid oozes out from the end of proboscis when the proboscis is attached to the sieve tube of a plant. This liquid contains sugars and amino acid, which proves that translocaion of these substances occurs in sieve tubes of phloem.
2. Expose plant to CO2 radioactive carbon-14 for photosynthesis. The sugars formed contain the radioactive carbon-14 which can be detected by photographic film. It is found that the traces of this carbon occurs in phloem.