How to Revise Biological molecules — OCR A-Level Biology
Biological molecules is a topic in the OCR A-Level Biology specification. This guide covers learning objectives, examiner tips, common mistakes, and key terminology to help you revise effectively.
Examiner Tips for Biological molecules
- Ensure you can draw and label the general structure of an amino acid.
- Practice calculating Rf values and interpreting colorimeter data.
- Be prepared to explain how the structure of a molecule (e.g., cellulose) directly enables its function (e.g., structural support).
- Memorize the specific chemical elements present in each class of biological molecule.
- Use the correct terminology for chemical tests (e.g., 'reducing sugar' vs 'non-reducing sugar').
Common Mistakes in Biological molecules
- Confusing condensation and hydrolysis reactions.
- Incorrectly identifying the structural differences between alpha and beta glucose.
- Failing to link the specific properties of molecules (e.g., cellulose, glycogen) to their biological functions.
- Misinterpreting Rf values or failing to label axes correctly in chromatography experiments.
- Confusing the roles of different types of bonds (glycosidic, ester, peptide, hydrogen, disulfide, ionic) in different molecules.
Key Marking Points
- Hydrogen bonding in water and its roles as a solvent, transport medium, and coolant.
- Monomer and polymer concepts, including condensation and hydrolysis reactions.
- Chemical elements (C, H, O, N, S, P) in biological molecules.
- Structure of glucose (alpha/beta), ribose, and formation of glycosidic bonds in disaccharides and polysaccharides.
- Structure of starch (amylose/amylopectin), glycogen, and cellulose related to their functions.
- Structure of triglycerides and phospholipids (ester bonds, hydrophobic/hydrophilic regions).