October 21, 2019 / by ntweedle

Common Mistakes in A-level Biology

common mistakes in A-level Biology

Common mistakes A-level Biology students make during their Year 13 studies


If you’re hoping for the best grades possible for A-level Biology, it’s essential to avoid these common mistakes. So if you’re aspiring to study at a top red brick university, read on while ensuring that you tighten up on terminology and you’ll see your grades soar!


    • ATP isn’t energy, ATP releases energy in small, manageable amounts.
    • ATP synthase is the enzyme required during oxidative phosphorylation NOT ATPase. ATP synthase is embedded in the mitochondrial membrane and allows protons to move down their electrochemical gradient across the inner mitochondrial membrane and into the mitochondrial matrix. This movement drives the synthesis of ATP from ADP and Pi. 
    • During both respiration and photosynthesis, redox reactions take place. You must be able to incorporate the terms oxidation, dehydrogenation and reduction into your examination answers correctly. If a molecule is reduced, such as NADP to reduced NADP, it gains electrons, so may have gained hydrogen or lost oxygen. If a molecule is oxidised or dehydrogenated, such as reduced NAD to NAD, it has lost electrons so may have lost hydrogen or gained oxygen. 
    • When discussing nervous communication, take care with referring to nerve impulse transmission or action potentials, DO NOT use the terms messages or signals.
    • If you are discussing a process be as specific as possible with the level of detail you include, for example, name the stage and the location. In the kidneys, selective reabsorption takes place as glomerular filtrate flows along the proximal convoluted tubule of the nephron. 
    • Glycogen and glucagon are terms that frequently get muddled. Glycogen is the storage polysaccharide in mammals formed during glycogenesis from glucose in both the liver and muscle cells. This action is triggered by the secretion of insulin by Beta cells in the Islets of Langerhans located in the pancreas, lowering blood glucose concentration.  Glucagon is a hormone released by alpha cells in the Islets of Langerhans when blood glucose levels are low. Glucagon triggers glycogenolysis by binding to receptors on the cell surface membrane of liver and muscles cells activating enzymes that break down glycogen into glucose. Glucagon also activates enzymes that will trigger the formation of glucose from glycerol and amino acids. This process is known as gluconeogenesis. 


  • Dihybrid crosses whether they involve epistasis, linkage or neither, will always involve writing out the possible gametes. If we are considering the inheritance of 2 characteristics controlled by 2 different genes i.e. a genotype may be AaBb (diploid-4 alleles involved), then the gametes (haploid-2 alleles involved) will contain half the genetic material so AB, Ab, aB, ab are the 4 possible combinations. 1 allele must be present from each characteristic so you CANNOT have AA, BB, aa, bb. 


Nicky Tweedle, 22/09/2019


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