This is an summary of past synoptic essay titles for AQA A level Biology, along with some ideas of subjects that could be included in each essay. The first few essay titles are discussed in more depth, and later ones have bullet pointed subject ideas
Quaternary structure, 4 polypeptide chains, haem groups, co-operative binding – link to partial
pressure of oxygen in alveoli and lungs
Oxygen is the final electron acceptor in oxidative phosphorylation, this enables the electron chain to
continue and produce lots of ATP for metabolism and active transport
COHESION-TENSION THEORY (transport of water)
Transpiration of water from stomata creates a negative pressure, pulls the water column up, draws
the xylem narrower. Adhesion and cohesion occurs due to hydrogen bonds within the water
molecule.
Water is a reactant in photosynthesis, therefore needed by all cells containing chloroplasts. In
photolysis light splits water into electron, hydrogen ion and O2. The H+ and e- are used to produce
ATP and NADPH needed for the Calvin cycle for TP to then make hexose sugars
ABSORPTION (Glucose)
Co-transport of glucose. Na+ actively transported out of epithelial cell into blood to create a
concentration gradient from ileum to cell. Glucose and Na+ then bind to a co-transport protein and
diffuse into epithelial cell. Glucose moves into capillary by facilitated diffusion
Glucose is a reactant in aerobic and anaerobic respiration during glycolysis to produce pyruvate.
Results in ATP production for metabolism
ACTION POTENTIALS (Na+/K+)
Stimulus provides the energy to open sodium channels allowing Na+ to diffuse in. When a threshold
of +40mv is reached inside the axon, the sodium channels close and the potassium ion channels
open, so the axon becomes hyperpolarised. The action potential travels the length of the axon and
causes release of neurotransmitter into the synapse. This allows the neuron to communicate with
other neurons
This allows the flow of information along the cells of the nervous system and allows us to respond
to stimuli
TISSUE FLUID
High hydrostatic pressure at arteriole end so small molecules are forced out. This allows tissue fluid
to bathe the cells. Large proteins remain which causes a lower water potential. This means water is
reabsorbed by osmosis, and any remaining goes into the lymph system.
This allows all the cells to receive glucose and oxygen for respiration to produce ATP for metabolism.
It also means waste can be removed such as CO2 to prevent acidic conditions which may denature
enzymes
Importance of nitrogen in biological molecules eg ATP in metabolism
PATHOGENS (Immunity)
Humoral response – B lymphocytes, T helper cells, clonal expansion, memory cells and plasma cells
Knowledge of primary and secondary response has been used to create vaccines, so if re-infected
with the same pathogen then large quantities of antibodies can be created rapidly to provide
immunity.
GENETIC MODIFICATIONS (insulin production)
The vector (plasmid) comes from bacteria, and bacteria are the host to grow the insulin
This enables genetically modified products to be produced, such as insulin, which is used to treat
Type 1 diabetes. This is an improvement on previous methods of creating insulin which were
unethical as it used animals such as pigs. It also enables it to be made in larger quantities, and as it is
human insulin it has less side effects and shouldn’t be rejected by the body.
NATURAL SELECTION (antibiotic resistance)
Describe the process of natural selection. Directional selection – when one of extreme trait is
favoured and those alleles become more common. Antibiotic resistance in bacteria is an example of
this
Whilst not beneficial to humans, antibiotic resistance has enabled the bacteria populations to
become adapted to their environment and survive despite exposure to antibiotics
STUDYING DNA REPLICATION
PCR (thermophilic bacteria)
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