OCR A-Level Biology - Modules 1-4 Questions And 100% Correct Answers 2025

OCR A-Level Biology - Modules 1-4 Questions And 100% Correct Answers 2025 why do specimens need to be thin when observing them under a light microscope? - Correct Answer to allow light to pass through identify and explain the starch test - Correct Answer add iodine dissolved in potassium iodide solution to the sample - positive test = blue-black - negative test = orange-brown why is the structure of the plasma membrane often referred to as the fluid mosaic model? - Correct Answer - the continuous bilayer is 'fluid' as the phospholipid molecules are constantly moving - protein molecules are scattered through the bilayer like a mosaic why is cell signalling important? - Correct Answer so that cells can communicate with each other how do cells communicate? - Correct Answer - one cell releases a messenger molecule by exocytosis - the molecule travels in the blood to another cell - messenger molecule is detected by another cell as it binds to the receptor on the plasma membrane why is cell signalling specific? - Correct Answer different receptors are specific to different molecules what does cell signalling initiate? - Correct Answer a physiological response