CHAPTER 2: CELL STRUCTURE AND CELL ORGANISATION
UNICELLULAR
(Amoeba sp.)
Amoeba live in freshwater
Constantly changing shape in response to stimuli
Use pseudopodium (false feet) for movement and feeding
Cytoplasm is 2 layers, inner (endoplasm) and outer (ectoplasm)
Pseudopodia also used for eating, surrounding food (phagocytosis), packaging it in a food vacuole and digests it with lysozyme (lysosomeenzyme)
Exchange of substances through plasma membrane by diffusion
Water goes into the cell by osmosis and fills the contractile vacuole, when full, blows out the water from time to time(osmoregulation)
Amoeba sp. reproduces by binary fission, but produces spores when cannot do binary fission MULTICELLULAR1.
Cells grow, change shape and differentiate in multicellular organisms.2.
Mature cells carry out different functions, like different medical specialists are experts in their field, like a cardiologist in the heart, the neurologist in the brain, etc.3.
They undergo specialization to carry out their functions more efficiently.4.
Organisation is in this form:C EL L C O M P O N EN TS Plasma membrane ⇝ semi-permeable
⇝ regulates the movement of substance Cytoplasm biochemical reactions and living process
occurs
Cell wall mechanical strength and support plant cells
Vacuoles plant elongation
Nucleus controls the activities of the cell Mitochondria release energy and sites for cellular
respiration Ribosomes sites for protein synthesis
Endoplasmic reticulum Smooth ER ⇝synthesize lipids Rough ER ⇝ transport proteins Golgi apparatus processing, packaging and transport centre
Lysosomes digestive compartments in a cell Centrioles (animal
cell) cell division
Chloroplasts captures energy for photosynthesis
Os moregul a ti on – Regul a te wa ter
n
o
n
-o
rg
an
ell
es
5.
Cells that carry out a function are grouped into tissues.6.
Different tissues that carry out a function are grouped into an organ.7.
Several organs that contribute to one section of an organism’s functions (circulatory, muscular) are grouped into a system.8.
Several systems make up an organism. ANIMALSThere are 4 main types of tissue in an animal:
Tissues work together to perform a specific function. These are called organs. Examples are lungs, heart, kidneys, brain etc.
Example: The skin:
Consists of various tissues joined together 2 main layers, the epidermis and the dermis
Epidermis is made of epithelial tissue, which constantly divides Dermis is made of connective, nerve, epithelial and muscle tissue Blood is supplied through blood capillary network
Nerve endings are scattered throughout the skin, transmit impulses to nervous system
Epithelial cells produce hair follicles, sweat glands and oil glands
PLANTS
Two main types of tissue in plants: Meristematic tissue
o Consists of small cells with thin walls, large nuclei, dense cytoplasm and no vacuoles
o Young, actively dividing cells, undifferentiated, located at root tips and shoot buds
Permanent tissue
o Differentiated/partly differentiated mature tissues o Three types of permanent tissue:
Epidermal tissue
Ground tissue (parenchyma, collenchyma, sclerenchyma) Vascular tissue ( xylem tissue, phloem tissue)
Organs in plants are leaf, stem, root and flower. Systems are root and shoot systems.
o Root system – all plant roots.
o Shoot system – stem, leaf, bud, flower and fruit. Stem, branch for support system.
Leaf for photosynthesis. Flowers for pollination.
Internal environment consists of blood plasma, interstitial fluid and lymph. Physical factors include temperature, blood pressure and osmotic pressure. Chemical factors include pH, salt and sugar content.
Homeostasis is maintenance of constant internal environment for optimal cell performance.
Any change in the internal environment will cause homeostasis to kick in and work to cancel the change. This is governed by the negative feedback mechanism.
Cell Tissue Organ System Multicellular
Organism Tissues in animals Epithelial tissues protection, secretion and absorption Muscle tissues (movement) ⇝Smooth muscle (intestine, blood vessels, urinary and
reproductive tract) ⇝ Skeletal muscle (arms and legs) ⇝ Cardiac muscle
(heart walls)
Connective tissues (bind structure, provide support and
protection) - Tendons -Ligaments - Cartilage - Bones - Blood Fat cells Nerve tissues (transmit nerve impulses, control and coordiante body activities) - neurons →dendrites and axons
CHAPTER 3: MOVEMENT OF SUBSTANCE ACROSS THE PLASMA MEMBRANE
The structure of the plasma membrane (fluid mosaic model) Function: regulates the exchange of
substance between the content of a cell and the external environment
A polar head is attracted to water
A pair of non- fatty acid tails is repelled by water
Molecules that can move freely across the plasma membrane by simple
diffusion
Molecules that cannot move freely across the plasma membrane and require
the aid of transport protein (pore proteins and carrier protein) Lipid-soluble molecules (A,D,E,K,
glycerol)
Water-soluble molecules (glucose, amino acids)
Water Inorganic ions ( K+, Na+, Ca2+) Small uncharged molecules (O2 and CO2)
Movement of substance across the plasma membrane
Differences between Passive Transport and Active Transport PT (osmosis, facilitated and simple
diffusion)
AT
Does not require energy Require energy from cell respiration Substances move with concentration
gradient
Substances move against concentration gradient
Will continue until an equilibrium is reached
Process leads to accumulation or elimination of the substance from the
cell
Osmosis
The movement of water
molecules from region of their
higher concentration to a
region of their lower
concentration through a
semi-permeable membrane.
Simple diffusionThe movement of particles (molecules or solutes) within a gas or a liquid from a region of high concentration to a region of lower concentration.
Hydrophilic head
Hydrophobic tails
Wa ter s oluble s ubstances such as gl ucose and amino a cids and ions need to aid by ca rrier protein. Wa ter molecules can move across pl a sma membrane.
The pl asma membrane is generally described as s emi-permeable or selectively permeable because it only l ets certa i n substances through.
Facilitated diffusion
The movement of hydrophilic molecules or ions across the plasma membrane with the help of transport proteins.
Active transport
The movement of particles across the plasma membrane against the concentration gradient, that is from a region of low
concentration to a region of high concentration.
ANIMAL CELLS
Solutions Observation Discussion Condition
Hypotonic
⇝ water diffuses into the cell by osmosis ⇝the cell swell up and eventually burst
Haemolysis
Isotonic
⇝ water diffuses into and out of the cell at equal rate ⇝ no net movement of water Normal cell shape Hypertonic
⇝ water diffuses out of the cell by osmosis
⇝ the cell shrinks Crenation
PLANT CELLS
Hypotonic
⇝ Water diffuses into the large central vacuole by osmosis. ⇝ The large central vacuole expands, causing the cell to swell.
Turgid
Isotonic
⇝ Water diffuses into and out of the cell at equal rates.
Normal cell shape
Hypertonic
⇝ Water diffuses out of the large central vacuole by osmosis. ⇝ Both the vacuole and cytoplasm lose water to
surroundings and shrink.
⇝ The plasma membrane pulls away from the cell
⇝Plasmolysis.
⇝The plant
cell becomes
flaccid and
less turgid.
Isotonic •Solutions with equalsolute concentration Hypertonic •Solution with a higher solute concentration Hypotonic •Solution with lower
The Effects and Applications Of Osmosis In Everyday Life 1. Wilting of plants
Problems can arise if chemical fertilisers are added in excess to the soil. The soil solution becomes hypertonic to the cell sap of the root hair cells. Water moves out of the plant by osmosis.
When flaccidity spreads throughout the plant, wilting occurs. 2. Preservation of foods
Food can be preserved by using salt or sugar.
When salt or sugar is added to the food, it creates a hypotonic condition for the microorganisms that spoil the food.
Water passes out from the microorganisms into the concentrated solution. This results in slower growth of the microorganisms or even death.
CHAPTER 4: CHEMICAL COMPOSITION OF THE CELL
ORGANIC COMPOUNDS Carbohydrates
(C,H,O)
1. Primary source of energy
2. Monosaccharides (Glucose, Fructose, Galactose) a. Reducing sugars
3. Disaccharides ( Maltose, Sucrose, Lactose) a. Joined together through condensation b. Break down by adding water (hydrolysis) c. Maltose & lactose ( reducing sugar) CHEMICAL COMPOSITION OF THE CELL Elements
(one atom)
Chemical compounds (more than two elements) Inorganic (x carbon) (eg: water) Organic (√ Carbon and hydrogen) Carbohydrates Monosaccharides Disaccharides Polysaccharides Lipids Fats Oils Waxes Phospholipids Steroids Proteins Enzymes Nucleic acid
Sucrose (non-reducing sugar) 4. Polysaccharides ( Starch, Cellulose, Glycogen) Lipids (C,H,O) 1. Fats and Oils
a. 1 glycerol: 3 fatty acids (saturated or unsaturated) 2. Waxes
3. Phospholipids (plasma membrane) 4. Steroids
a. Include cholesterol and hormones (progesterone, testosterone, oestrogen)
Proteins (C,H,O,N) 1. Made up of one or more polypeptides (monomers: amino acids – Essential and non-essential)
2. Broken down into amino acids by hydrolysis
3. Protein structures: Primary, Secondary, Tertiary, Quaternary Nucleic acids (DNA
and RNA)
1. Store genetic information) 2. Basic units ( nucleotides)
a. Nitrogenous base b. Pentose sugar c. Phosphate group INORGANIC COMPOUNDS Water 1. A polar molecule
2. Functions:
a. Medium for biochemical reactions b. Solvent
c. Transport medium
d. Providing support and moisture e. Maintain body temperature f. Lubrication
g. Maintaining osmotic balance and turgidity h. High surface tension and cohesion ENZYMES:
∆ Metabolism (anabolism and catabolism) ∆ Consists of intracellular and extracellular ∆ Biological catalysts ∆ Proteins ∆ Naming: -ase ∆ Uses: o Food processing o Tenderising meat o Detergent manufacturing General
charateristic Bind with substrate to produce product Not changed or destroyed
Highly specific
Needed in small amounts Metabolic reactions: Reversible
The activities can be slowed down or inhibited Require cofactors to function
Mechanism (Lock and Key)
Factors affecting the activity of enzymes
pH
⇝ Optimum pH (enzymatic reaction rate is the fastest) ⇝ Changing in pH, changing the charges on active site causing reducing the ability of both molecules to bind
Temperature, ° C ⇝ Low ° C, slow reaction
⇝ ↑the temperature every 10° C, the reaction is doubled until the optimum temperature is reached
⇝ Max ° C will causing the enzyme to denatured Substrate concentration, [subs]
⇝ Low [subs], rate of reaction increases with the [subs] ⇝ Increase [subs], more products are formed, increase rate of reaction
⇝ Constant rate, enzyme is saturated, all active sites are filled up Enzyme concentration, [enzyme]
⇝ reaction rate is directyly proportion to the [enzyme] until maximum rate is achieved
