CIE IGCSE Biology: 复习笔记：3.1.8 Proteins & Active Transport
- Energy is needed because particles are being moved against a concentration gradient, in the opposite direction from which they would naturally move (by diffusion)
- Active transport is vital process for the movement of molecules or ions across membranes
- uptake of glucose by epithelial cells in the villi of the small intestine and by kidney tubules in the nephron
- uptake of ions from soil water by root hair cells in plants
- Active transport works by using carrier proteins embedded in the cell membrane to pick up specific molecules and take them through the cell membrane against their concentration gradient:
- Substance combines with carrier protein molecule in the cell membrane
- Carrier transports substances across membrane using energy from respiration to give them the kinetic energy needed to change shape and move the substance through the cell membrane
- Substance released into cell
Carrier proteins in active transport.
You don't need to know anything about the phospholipid bilayer when it comes to active transport!