Unit 3.1 the importance of ATP

  • 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


No comments have yet been made