Aiming for top grades in A-level Biology? Do you want to know the areas where students frequently lose marks, so you can avoid it happening to you? Tighten up on terminology and you’ll see your grades soar! In this blog article we’ll be looking at common mistakes A-level students make during their AS studies.

• Always take measurements for magnification calculations in mm NOT cm, then carry out any conversions before inserting into the formula.
• Test for starch uses iodine in potassium iodide NOT iodine solution.
• Protein denaturation involves hydrogen and ionic bonds being broken NOT peptide bonds.
• Take care when using the term active site, this is only a term used when referring to an enzyme. Binding site should be used for antigens and antibodies, receptors and hormones. 
• Don’t confuse the source and the sink in the theory of translocation. The source is where the sucrose is produced and actively loaded into the sieve tube element. The sink is where the sucrose is used, usually a growing region, such as a shoot tip. 
• Understand the difference between tissue fluid and lymph. Tissue fluid is the fluid that surrounds cells in tissues. It is composed of small molecules that can leave the blood plasma such as glucose, oxygen and water. Whereas lymph is the excess tissue fluid that drains into the lymph vessels to be returned to the circulatory system. 
• Don’t confuse channel and carrier proteins. Channel proteins form a pore in a cell membrane and allow facilitated diffusion of charged particles; they do not change shape. Carrier proteins allow facilitated diffusion of large molecules and change shape to allow this movement. 
• What is the difference between a gene and an allele? A gene is a length of DNA coding for a polypeptide. An allele is an alternative form of a gene e.g. A (dominant) or a (recessive).  
• When you are explaining osmosis remember at A-level it is necessary to refer to water potential not concentration. Hence, osmosis is the diffusion of water molecules across a partially permeable membrane from an area of higher water potential to an area of lower potential.
• Know the difference between mitosis and meiosis. Mitosis is the process where a parent cell divides to produce 2 genetically identical daughter cells. Meiosis is where a parent cell divides to produce 4 genetically different haploid cells. 

Nicky Tweedle, 19/9/2019