Biology 0610 Biological Processes

All the processes that require long answer

Describe diffusion

1. Location A has lower concentration of particles; Location B has higher concentration

2. More particles will diffuse from a region of high concentration to a region of low concentration

3. Particles diffuses from B to A, down the concentration gradient

Describe osmosis

1. Location A has low water potention; Location B has high water potential

2. Water molecules will move from a region of higher water potential to region of lower water potential

3. Water diffuses from B to A through partially permeable membrane by osmosis

Describe active transport

1. Location A has lower concentration of particles; Location B has higher concentration

2. Particles move through protein carriers on cell membrane,

3. from a region of low concentration to a region of high concentration,

4. using energy from respiration

5. Particles move from A to B, against the concentration gradient

Describe enzyme action

1. Enzyme is a biological catalyst that speeds up the chemical reaction

2. Substrate will bind to the active site of the enzyme, forming enzyme-substrate complex

3. the shape of the active site of enzyme is complementary to the substrate

4. the specificity of enzymes to substrate is like a lock and key

5. product will form from the enzyme-substrate complete after the reaction is completed

6. Enzyme will remain the same after the reaction

Describe the digestion of food through the alimentary canal

1. Food is ingested at mouth

2. Teeth break down food mechanically via chewing & crushing

3. Saliva contains amylase which helps to digest starch to maltose

4. Peritalsis push food bolus down the oesophagus

5. Stomach churning will break food further

6. Protease & pepsin breaks down protein to amino acids

7. In small intestines, trypsin breaksdown protein,

8. Bile emulsify fats & oils to increase surface area for chemical digestion

9. Lipase breaks down fats & oils to glycerol and fatty acids

10. Maltase breaks down maltose to glucose

11. Digested nutrient will be absorbed from intestines into blood

12. Large intestines further absorb water from undigested mass

13. Absorbed nutrients will assimilate and use by cells

14. Undigested food will be removed via egestion as faeces

Outline the pathway taken by water through the root, stem and leaf

1. Water & mineral ions absorbed through root hair cells

2. Water enter via osmosis

3. Mineral ions enter via active transport

4. Water then pass through root cortex cells into xylem

5. Water moves upwards in the xylem due to transpiration pulls

6. Transpiration pulls draw up a column of water molecules held together by forces of attraction between the molecules

7. Water in the xylem enter mesophyll cells for photosynthesis

Describe the functioning of the heart

1. Deoxygenated blood enters the right atrium via the vena cava

2. Atrium muscles contract, blood moves through the atrio-ventricular valve into the right ventricle

3. The right ventricle muscles contract and blood leaves via the pulmonary artery, towards the lungs

4. Oxygenated blood enters the left atrium via the pulmonary vein

5. The muscles of the left atrium contract and it moves through the atrio-ventricular valve into the left ventricle

6. The left ventricle muscles contract and blood then leaves the heart via the aorta, where it goes to the rest of the body to supply oxygen

7. Finally, it returns again to the heart via the vena cava, and the cycle continues.

Describe the process of clotting

1. The is a cut in blood vessel

2. Platelets coagulate at cut and form a temporary plug

3. Platelet release enzyme, turning soluble fibrinogen into insoluble fibrin

4. Fibrin forms a mesh over the cut

5. Red blood cells & platelets are trapped by the mesh, and form a clot

6. Clot dried and becomes a scab

Outline the process of vaccination

1. Weakened pathogens or their antigens are injected into the body

2. The antigens stimulate an immune response by lymphocytes which produce antibodies

3. Memory cells are produced, this gives long-term immunity

4. Active immunity is gained

5. Vaccination helps control spread of diseases

Describe cholera as a disease

1. Cholera bacterium is transmissted in contaminated water

2. Cholera produces a toxin that causes secretion of chloride ions into the small intestines

3. This cause water potential of small intestines to lower

4. Water moves from nearby cells into the gut via osmosis

5. Faeces becomes watery

6. Causing diarrhoea, dehydration, loss of ions in the blood

Explain the link between physical activity and rate and depth of breathing

1. Physical activity use energy

2. Rate of respiration increases to provide energy

3. The increase of carbon dioxide concentration in the blood is detected by brain

4. Due to negative feedback, this leads to an increased rate and greater depth of breathing

5. Rate of gas exchange increased at alveoli

6. Excess carbon dioxide is removed, and more oxygen enters the blood

Outline how the oxygen debt is removed after exercise

1. During vigorous exercise, oxygen is used up and anaerobic respiration occurs

2. Lactic acid builds up in muscles and blood causing oxygen debt

3. After exercise, heart rate remains fast to transport lactic acid in the blood and muscles to the liver

4. Deeper and faster breathing continues on to supply oxygen for aerobic respiration of lactic acid in liver

Explain excretion in kidney

1. Blood is filtered in the glomerulus

2. Large molecules is filtered, while small molecules pass through and return to blood

3. Ultrafiltration removes water, glucose, urea, and ions into the Bowman’s capsule.

4. Reabsorption of all glucose, most water and some ions occurs in the nephron

5. Molecules are reabsorbed via active transport

6. Remaining substances form urine (contains urea, excess ions, and water).

7. Urine travels down the ureter to the bladder, then is excreted via the urethra.

Describe a simple reflex arc

1. Receptor detects a stimulus and generates an electrical impulse.

2. Sensory neurone carries the impulse from the receptor to the spinal cord

3. Relay neurone (in the spinal cord) transfers the impulse from the sensory neurone to the motor neurone

4. Motor neurone carries the impulse from the spinal cord to the effector (muscle or gland).

5. Effector carries out the response

Describe the events at a synapse

1. An impulse stimulates the release of neurotransmitter molecules from vesicles of pre-synaptic neurone into the synaptic gap

2. Neurotransmitter molecules diffuse across the gap

3. Neurotransmitter molecules bind with receptor protein on post-synaptic neurone

4. Recetor protein is complementary to the neurotransmitter molecules

5. An impulse is then stimulated in post-synaptic neurone

Explain accommodation to view near and distant objects

To view a near object,

1. Ciliary muscles contract.

2. Suspensory ligaments slacken.

3. Lens becomes thicker (more convex).

4. This increases the lens’s refractive power to focus light from a near object onto the retina.

To view a distant object,

1. Ciliary muscles relax.

2. Suspensory ligaments tighten.

3. Lens becomes thinner (less convex).

4. This reduces the refractive power to focus light from a distant object onto the retina.

Describe the control of blood glucose concentration by the liver and the roles of insulin

1. After meal, blood glucose becomes high

2. Glucose receptors (chemoreceptors) in islets of Langerhans in pancreas detect changes in blood glucose concentration

3. Pancreas secretes insulin

4. Insulin stimulates the liver and muscle cells take up glucose from blood

5. Insulin stimulates the liver and muscle cells to convert glucose into glycogen

6. This lowers the blood glucose concentration back to normal.

Describe the control of blood glucose concentration by the liver and the roles of glucagon

1. After fasting, blood glucose becomes low

2. Glucose receptors (chemoreceptors) in islets of Langerhans in pancreas detect changes in blood glucose concentration

3. Pancreas secretes glucagon.

4. Glucagon stimulates the liver to break down glycogen into glucose, and release glucose into the blood

5. This raises the blood glucose concentration back to normal

Describe the maintenance of a constant internal body temperature in mammals when hot

1. Human maintains stable body temperature through a process called thermoregulation

2. When body is too hot, hypothalamus in the brain detects temperature changes

3. Hypothalamus sends nerve impulses to effectors (sweat glands, muscles, blood vessels) to correct the change.

4. Sweat glands secrete sweat onto the skin.

5. Sweat evaporates, removing heat and cooling the body.

6. Muscles move as we move to seek shade, reducing activity and drinking fluids.

7. Vasodilation occurs

Describe the maintenance of a constant internal body temperature in mammals when cold

1. Human maintains stable body temperature through a process called thermoregulation

2. When body is too cold, hypothalamus in the brain detects temperature changes

3. Hypothalamus sends nerve impulses to effectors (sweat glands, muscles, blood vessels) to correct the change.

4. Muscles contract rapidly to increase respiration, which releases heat to warm the body.

5. Fatty tissue under the skin acts as an insulator, reducing heat loss.

6. Hair erector muscles contract, making the hair stand to provide further insulation.

7. Vasoconstriction occurs

Describe the maintenance of a constant body temperature in mammals' skin in hot weather

1. When the environment is too hot, thermoreceptor in the skin detects temperature changes

2. Receptor sends a nerve impulse through sensory to the hypothalamus

3. Hypothalamus sends nerve impulses to effectors (sweat glands, muscles, blood vessels) to correct the change.

4. Shunt vessels constrict, so more blood flows through skin surface capillaries.

5. Vasodilation occurs, the arterioles supplying skin capillaries widen,

6. More blood flows near the skin surface

7. More heat is loss by radiation to cool the body

Describe the maintenance of a constant body temperature in mammals' skin in cold weather

1. When the environment is too cold, thermoreceptor in the skin detects temperature change

2. Receptor sends a nerve impulse through sensory to the hypothalamus

3. Hypothalamus sends nerve impulses to effectors (sweat glands, muscles, blood vessels) to correct the change.

4. Shunt vessels dilate, so blood is diverted away from skin surface capillaries.

5. Vasoconstriction occurs, the arterioles supplying skin capillaries constrict

6. Less blood flow to the skin surface

7. This minimises heat loss, to conserve body temperature.

Explain the role of auxin in controlling shoot growth

1. Auxin is made in the shoot tip

2. Auxin diffuses through the plant from the tip

3. Auxin accumulates on the shaded side of the shoot.

4. This causes cells on the shaded side to elongate more, making the shoot bend towards the light.

5. Plant shoot shows positive phototropism

6. Auxin accumulates on the lower side of the horizontal shoot due to gravity.

7. More elongation occurs on the lower side, causing the shoot to bend upwards.

8. Plant shoot shows negative gravitropism

Explain the role of auxin in controlling root growth

1. Auxin is made in the shoot tip

2. Auxin diffuses through the plant from the shoot tip

3. Auxins collect on the lower side of the root due to gravity.

4. In roots, high auxin levels inhibit cell elongation, so the root bends downward.

5. Plant root shows positive gravitropism

6. Auxin moves to the shaded side, but in roots it inhibits cell elongation.

7. The cells on the brighter side grow more, so the root bends away from light.

8. Plant root shows negative phototropism

Describe the growth of the pollen tube and its entry into the ovule followed by fertilisation

1. After pollination, a pollen grain lands on the stigma.

2. It grows a pollen tube down through the style toward the ovary.

3. The pollen tube carries the male nucleus from the pollen grain.

4. The tube enters the ovule through a small opening called the micropyle.

5. The male nucleus fuses with the female nucleus (in the ovule); this is fertilisation.

6. A zygote is formed, which will develop into an embryo/seed

Explain how a protein is made

1. The gene that codes for the protein is found in the nucleus and does not leave it.

2. A messenger RNA (mRNA) molecule is made as a copy of the gene.

3. The mRNA is made in the nucleus, then moves into the cytoplasm.

4. In the cytoplasm, the mRNA passes through a ribosome.

5. The ribosome assembles amino acids into a protein molecule.

6. The sequence of amino acids in the protein is determined by the sequence of bases in the mRNA.

Explain how to use test cross to identify an unknown genoype

1. A test cross is used to determine whether an organism showing a dominant trait is homozygous dominant (e.g. TT) or heterozygous (e.g. Tt).

2. The organism with the unknown genotype is crossed with a homozygous recessive individual (e.g. tt).

3. If all offspring show the dominant trait, the unknown genotype is likely homozygous dominant (TT).

4. If some offspring show the recessive trait, the unknown genotype is heterozygous (Tt).

Describe natural selection

1. There is genetic variation within a population

2. The variation may be caused by mutation

3. Individuals within the population competes for resources

4. Individuals with advantageous features adapt better to the environment and survive

5. Survived individuals have more chance to reproduce

6. These individuals pass on their alleles to the next generation

7. Over time, this alleles become more common within population

Describe the development of strains of antibiotic resistant bacteria

1. Random mutations occur in the DNA of some bacteria, resulting in genetic variation, causing some bacteria are resistant to antibiotics.

2. Antibiotics (selection pressure) kill non-resistant bacteria, but resistant ones survive.

3. Resistant bacteria reproduce, passing on the resistance gene.

4. Over time, most of the population becomes resistant.

5. This is evolution by natural selection—the resistant trait becomes common.

6. New antibiotics are needed as resistant strains spread.

7. This process can repeat, leading to multi-drug resistant bacteria (e.g., MRSA).

Describe selective breeding

1. Humans select individuals with desirable features

2. Selected individuals are crossed (bred) together to produce the next generation.

3. Offspring showing the desirable features are selected and bred again.

4. Repeat the process over many generations.

5. Over generation, the desired allele becomes common

Explain the process of eutrophication

1. Excess fertiliser is washed into the waterway

2. This causes an increased availability of nitrate and other ions

3. Nitrate ions are needed for plant growth

4. Algae bloom occurs

5. Algae covers the surface of the water, blocking sunlight from underwater plants

6. Plants cannot photosynthesise to produce energy so they die.

7. The dead plants are broken down by decomposers

8. The increased aerobic respiration by decomposers used up the oxygen in the water

9. Dissolved oxygen in water is drastically reduced

10. This causes the death of organisms requiring dissolved oxygen in water

Outline the process of genetic modification

1. The DNA making up the desired human gene is isolated using restriction enzymes

2. This forms sticky ends on the cut out gene

3. A bacterial plasmid DNA is cut with the same restriction enzymes, forming complementary sticky ends

4. Human DNA is inserted into bacterial plasmid DNA using DNA ligase to form a recombinant plasmid

5. Recombinant plasmids are inserted back into bacteria

6. Bacteria containing recombinant plasmids multiply

7. The human gene in the bacteria is expessed to make human protein