C1- The Importance of ATP Flashcards
Why is ATP described as the ‘universal energy currency’?
It is used in all cells to drive their reactions.
When is ATP made?
When energy becomes available e.g. in respiration and the light dependant reactions of photosynthesis.
When is ATP broken down?
When a cell needs energy e.g. in biosynthesis, muscle contraction and powering the membrane Na^+/K^+ pumps.
Hoe is ATP suited to its role?
- is inert
- 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
Define Chemiosmosis.
The flow of protons down an electrochemical gradient, through ATP synthetase, coupled with the synthesis of ATP from ADP and a phosphate ion.
Describe the pathway electrons take and how this allows energy to be available for the formation of ATP.
(chemiosmosis)
- electrons from hydrogen atoms are transferred from a donor molecule to a recipient.
- a sequence of relations transfers the electrons from one molecule to the next along a chain
- each transfer is a redox reaction- one molecule loses e^- while the other gains them.
- oxidation reactions make energy available, which is used to synthesise ATP.
Describe the pathway hydrogen atoms take to synthesise ATP.
chemiosmosis
- energy release from oxidation pumps the protons from the hydrogen atoms across a membrane so that they are more concentrate on one side than the other.
- the difference is concentration and charge between the two sides of the membrane create an electrochemical gradient- so is a source of potential energy.
- protons flow back down the gradient in a process called chemiosmosis, through the enzyme ATP synthetase.
- the energy release when they do is converted into ATP.
How do bacteria establish a proton gradient?
- they do not have an internal membrane so use the cell membrane to create a proton gradient.
- They pump protons out into the cell wall
Where is a proton gradient established during respiration?
In the inner membranes of the mitochondria.
Where is the proton gradient established during photosynthesis?
In the thylakoid membranes of the chloroplast.
Why are membranes that are used to create a proton gradient described as ‘sealed membranes’?
- They only let protons through in a highly controlled fashion.
- Protons are very small and easily pass through water molecules so the membranes must also be watertight.
Describe how the ATP is made to allow the light dependant reaction of photosynthesis to occur.
- electrons are exited by energy from light
- the 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- protons flow back down the electrochemical gradient into the storm through ATP synthetase
- the energy is incorporated into ATP
- ATP drives the light-independent reactions of photosynthesis and energy is incorporated into macromolecules made by the cell
Briefly describe how ATP is made during respiration.
- electrons are excited by the 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 creating a proton gradient
- energy is released in chemiosmosis, as protons flow back into the matrix through ATP synthetase and is incorporated into ATP
- energy not incorporated into ATP is lost as heat.
What occurs is you disrupt the proton gradient?
death
What is apoptosis?
- programmed cell death
- occurs during embryonic development for example
- operates by preventing proton gradients across cell membranes from forming
