Importance of ATP Flashcards
why is ATP the universal energy currency?
all types of cells use ATP as the energy to drive their reactions
when is ATP broken down?
when cells need energy
e.g. biosynthesis, muscle contraction, powering the membrane pumps
when is ATP made?
when energy becomes available
e.g. in respiration, in light dependent reactions of photosynthesis
why is ATP suitable for its role?
- is inert
- can pass out of mitochondria into the cytoplasm
- releases energy efficiency
- releases energy in useable quantities, little wasted as heat
- easily hydrolysed to release energy
- readily reformed by phosphorylation
what is chemiosmosis?
the flow of protons down an electrochemical gradient, through ATP synthetase, coupled with the synthesis of ATP from ADP and a phosphate ion
pathway of electrons in the synthesis of ATP
- electrons from hydrogen atoms transfer from donor molecule to recipient
- sequence of reactions transfer the electrons along a chain of molecules
- each is a redox reaction, one molecule oxidised the next is reduced
- oxidation reactions make energy available, used to synthesise ATP
pathway of protons in the synthesis of ATP
- energy released from oxidation pumps protons from hydrogen atoms across a membrane
- protons more concentrated on one side
- the difference in proton conc and the charge on either side produces an electrochemical gradient, source of potential energy
- protons flow down this gradient, in chemiosmosis
- energy released is converted into chemical energy in ATP
mitochondria and chloroplast membranes
- bacteria don’t have internal membranes so use cell membrane to establish a proton gradient (pump protons out into cell wall)
- respiration uses inner membranes of mitochondria
- photosynthesis uses chloroplast thylakoid membranes
- these membranes support the theory of endosymbiosis
- membranes only let protons through in a controlled fashion
- as protons are small = easily pass through water molecules = membranes must be watertight = sealed membrane
proton gradient in light-dependent stage of photosynthesis
- electrons are excited by energy from light
- electrons move through carriers in thylakoid membranes, their energy pumps protons from stroma into spaces between thylakoid membranes
- energy is released in chemiosmosis and incorporated into ATP
- ATP drives the light independent reactions
- energy is incorporated into macromolecules made by the cell
proton gradient in respiration
- electrons excited by energy derived from food molecules
- energy is made available as they move through carriers on the inner mitochondrial membrane
- energy pumps protons across the membranes from matrix to inter membrane space = sets up proton gradient
- energy released in chemiosmosis
- energy incorporated into ATP or lost as heat
cell death from disrupted proton gradients
- apoptosis: programmed cell death. prevents proton gradients across cell membranes forming. e.g. in embryonic development
- DNP: mitochondrial poison. allows electron transport chain but not ATP synthesis (are uncoupled). e.g. to loose weight, body oxidises fats and carbs, all the energy released is converted to heat = no ATP made (body can overheat)
what is the electron transport chain?
- a series of proton carriers on the inner membrane of mitochondria and chloroplasts
- releases energy from electrons, incorporating it into ATP
respiration electron transport chain
- hydrogen atoms from respiratory breakdown of glucose are transferred by dehydrogenase enzymes to coenzymes NAD and FAD, and carried to mitochondria inner membrane
- electrons and protons of H atoms move through the ETC in different pathways
- for every 2 protons delivered by NADH = energy released to synthesis 3 ATP molecules
- reduced FAD delivering 2 protons releases energy for 2 molecules of ATP
oxidative phosphorylation
synthesising ATP by adding a phosphate ion to ADP using energy derived from oxidation reactions
photosynthesis electron transport chain
- photosystems transfer excited electrons to electron acceptors, then to protein carriers on thylakoid membranes
- protons from water and electrons are transferred to coenzyme NADP and GP (in pathway that synthesises carbohydrates)
- energy powering proton pumps and ETC in chloroplast comes from light
- chloroplasts synthesise ATP by photophosphorylation
