Edexcel A-level Biology Study Exam With All Correct Answers 2024.

Describe the events of fertilisation that occur after the acrosome reaction. - Answer -Membrane of sperm and egg cell fuse together -cortical granules release contents into zona pellucida -Zona pellucida thickens -Haploid nuclei fuse Explain how phospholipids form a cell surface membrane - Answer -Hydrophilic parts associate with water -Hydrophobic parts repel water -a bilayer forms with hydrophobic parts pointing in towards the centre of the bilayer Describe the role of the CFTR protein in ensuring that the mucus produced in the lungs has the right consistency - Answer -Chloride ions move out of the cells through the CFTR protein -Sodium ions then also move out of the cells -The concentration of the solute increases in the mucus -Water moves out of the cell by osmosis Describe how DNA is organised in a bacterial cell - Answer -Circular DNA that is not associated with histones -Plasmids -located in the cytoplasm Describe the light-dependent reactions of photosynthesis - Answer -Light energy excites a pair of electrons in PSII -Electrons used in the electron transport chain -Photolysis of water to produce H+, O2 and electrons