Biology Essay Questions

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1. The process of diffusion and its importance in living organisms Definition
Fick’s Law
Types of diffusion e.g. Facilitated diffusion, osmosis
Gas exchange in unicells, fish, mammals and plants
Digestion and absorption of products
Exchange of materials between blood in capillaries and tissues e.g. placenta Transpiration, root pressure, water and ion uptake by roots
Translocation and mass flow hypothesis
Osmoregulation by blood and kidney, unicells e.g. Amoeba
Action potentials
Synaptic transmission
Muscle action
Intracellular diffusion e.g. mitochondria, chloroplasts, enzyme action, DNA replication and protein synthesis
2. The different ways in which organisms use ATP OR ATP and its roles in living organisms The nature/structure of ATP and its importance as energy currency. Production and use of ATP in cytoplasm by glycolysis

Production of ATP by mitochondria in Krebs cycle and ETS – aerobic respiration. Anaerobic respiration.
Role of chloroplasts in ATP production via light independent reaction Uses e.g. Active transport (carrier protein shape changes), Nerve action (maintaining resting potentials via Na+/K+ pump and resynthesis of ACh), selective reabsorption by nephron, absorption by gut, Calvin cycle, muscle contraction (cross bridge formation), Biosynthesis of organic compounds, Contractile vacuoles, Translocation (loading of phloem), cell division (movement of chromosomes via spindle), CP formation in muscles, Nitrogen fixation (Bluegreen algae), Kidney function, movement of sperm, secretion of digestive enzymes in saprophytic fungi, cilia and flagella action

3. The movement of substances within living organisms (Jan 2003) OR Transport mechanisms in living organisms
Diffusion e.g. Ion movement in Roots, Synapse, within a cell, O2/CO2 in lungs and gills, factors affecting rate
Facilitated diffusion e.g. Glucose uptake, action potentials Osmosis e.g. Turgidity, uptake of water in plant roots, Kidney function Active Transport e.g. Na+/K+ pump, Cl- in RBC, Glucose uptake in intestine, mineral ions in plant roots, neurotransmitters into presynaptic membranes, carrier proteins, mechanism Endocytosis / exocytosis / Pinocytosis / phagocytosis e.g. Feeding in Amoeba Mass flow e.g. Phloem, Xylem, Peristalsis, Ventilation in lungs, gills and insect tracheoles, Bloodstream, Excretion, Cilia

Unusual ideas e.g. Chromosome movement during cell division, organelle movement in cells, Sliding filament theory, reproductive cells

4. Mutation and its consequences
Definition.
Types of mutation – addition, deletion, substitution.
Causes e.g. spontaneous, radiation, mutagenic chemicals.
Effect of mutation on protein synthesis.
A change in base sequence may result in a change in amino acid sequence of a polypeptide, which affects the protein structure and its function.
Metabolic blocks as a result e.g. PKU.
Mutation in CFTR gene in cystic fibrosis.
Haemophilia.
Somatic mutations e.g. cancer and germ line mutations e.g. colour blindness. Introns and exons – mutation may be removed by post-transcriptional modifications. Diploid carriers e.g. sickle cell anaemia.

The role of mutation in evolution e.g. sickle cell anaemia.
Mutation as a source of genotypic variation e.g. bacteria and antibiotics. Natural selection leading to changes in populations, changes within a species e.g. peppered moth, formation of a new species.

5. The properties of enzymes and their importance in living organisms OR The role of enzymes in living organisms
What is an enzyme?
How do enzymes work – lock and key theory/induced fit and lowering activation energy/enzyme substrate complexes.
Enzymes as proteins.
Effects of extremes of temperature and pH – optimums – graphs. Inhibition – competitive and non-competitive.
Activators, substrate concs.
Extra-cellular digestion - Fungal feeding.
Digestion in animals e.g. proteases, lipases, carbohydrases. Enzymes in chemical processes e.g....
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