This document contains sample questions and plans of topics you can talk about in your essay. This can be used for practice purposes for Paper 3 in Biology A-level 7401/7402.
Hope this helps.
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 (Blue-
green 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
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