A Level Edexcel Biology Midterm Exam Questions And Answers Graded A+ 2024.

What are target cells? - Answer Cells with receptor proteins on their cell surface membrane complimentary to the chemical What are meristems? - Answer Regions of actively dividing cells e.g. roots and shoots What do cytokinins do? - Answer promote cell division of stem and promote growth of lateral buds How do auxins cause cell elongation? - Answer Causes cell elongation by active transport of hydrogen ions into the cell walls, which lowers pH, making the cell walls flexible. Cells stretch to accommodate more water which leads to growth of the cell. What is Apical Dominance? - Answer The balance between auxins and cytokinins Auxin inhibits cytokinins effect on lateral growth. As the shoot grows up, the concentration of auxin decreases lower and lateral buds form What do auxins do? - Answer Promote cell elongation Promote growth of root laterally Suppresses growth of lateral buds What do gibberellins do? - Answer Promote cell elongation when auxins are present