AQA GCSE Biology Paper 1 - Revision Questions And Answers

How is the real size of a magnified image calculated? - Real size = Image size ÷ Total magnification. What is a eukaryotic cell? - A cell with DNA inside a membrane bound nucleus. Prokaryotic cells do not have a nucleus. Name two differences between a plant cell and a bacterial cell? - Plant cells have a nucleus / plant cells have mitochondria / plant cells have chloroplasts / plant cells have a cellulose cell wall whereas bacteria do not contain any of these structures. Bacteria have chromosomal DNA not in a nucleus and have DNA plasmids whereas plant cells do not contain these structures. How can the rate of diffusion be increased? - Higher temperature, Steeper concentration gradient, Shorter diffusion distance Why are stem cells used in medicine? - Treatment with stem cells may be able to help conditions such as diabetes and paralysis. What is the lock and key model of enzyme action? - The active site of an enzyme is a specific shape, which is complimentary to its substrate - they fit together like a lock and key to form an enzyme- substrate complex. What happens when an enzyme is denatured? - The active site changes shape and can no longer bind with the substrate. The enzyme will no longer function What is the test for a reducing sugar (such as glucose)? - Heated with Benedict's reagent. A change in colour from blue to green, orange or brick-red are all positive results.