- Created by: Ffion.H
- Created on: 28-10-19 21:18
- ATP is described as the universal energy currency.
- It is used in all cells to drive their reactions
- It is made when energy becomes available e.g. in respiration and in the light- dependant reactions of photosynthesis.
- It is broken down when the cell needs energy e.g. in biosynthesis, muscle contraction and powering membrane pumps.
ATP is ideally suited to its role because it:
- is inert (not chemically reactive)
- can pass out of mitochondria into the cytoplasm
- releases energy efficiently
- releases energy in useable quantities, so little is wasted as heat
- is easily hydrolysed to release energy
- is readily reformed by phosphorylation
Chemiosmosis: The flow of protons down an electrochemical gradient, through ATP synthetase, coupled with the synthesis of ATP from ADP and a phosphate ion.
The proton gradient
- Proton gradients occur in non-living systems, such as in oceanic alkaline hydrothermal vents.
- Proton gradients are a fundamental characteristic of all living things.
- In the light dependent stage of photosynthesis, electrons are excited by energy from light.
- These electrons move through a series of carriers in the thylakoid membranes.
- Their energy pumps protons from the stroma into the spaces between the thylakoid membranes.
- The energy is released in chemiosmosis, in which protons flow back down an electrochemical gradient into the stroma, through ATP synthetase.
- The energy is incorporated into ATP.
- This ATP drives the light independent reactions of photosynthesis and energy is incorporated into macromolecules made by the cell.
- In respiration, electrons are excited by energy derived from food molecules.
- Their energy is made available as they move through a series of carriers on the inner mitochondrial membrane.
- The energy pumps protons across the membrane, from the matrix into the inter-membrane space, setting up a proton gradient.
- Energy is released in…