role of ATP in living cells Flashcards
what is metabolism?
integrated set of enzymatic reactions compromising both anabolic and catabolic reactions
what is anabolism?
synthesis of complex molecules from simpler ones
what is catabolism?
- breakdown of energy rich molecules into simpler ones
- energy released if ‘captured’ as adenosine triphosphate (ATP) and stored for later used in anabolic reactions
what is energy required for?
- motions
- transport
- biosynthesis of essential metabolites
- thermoregulation
what is ‘free energy’?
- cells are isothermal systems
- heat flow cannot be used as a source of energy (heat can only do work when it passes to an area or an object at a lower temperature)
- free energy is acquired from nutrient molecules
what’s Gibbs free energy?
energy capable of doing work at constant temperature and pressure
what is enthalpy?
the heat content of the reacting system
what is entropy?
the randomness or disorder in a system
what is coupling of reactions?
an endergonic reaction can be driven in the forward direction by coupling it to an exergonic reaction through a common intermediate
what are the key facts/features of ATP?
- adenosine triphosphate
- ATP provides lots of the free energy required for anabolism
- ATP is the energy currency of the cell
- achieved by phosphate group transfer
- Gibbs free energy: the energy derived from the oxidation of dietary fuels to generate ATP
- energy is conserved as ATP and is transducer into useful work
what are ATP/ADP Mg2+ complexes?
- ATP in the cytosol is present as a complex with magnesium ions
- magnesium ions with the oxygen of the triphosphate chain making it susceptible to cleavage in the phosphoric transfer reactions
- magnesium ion deficiency impairs virtually all metabolism
what is substrate level phosphorylation (SLP)?
- formation of ATP by phosphate group transfer from a substrate to ADP
- known as SLP to distinguish form respiration-linked phosphorylation
- respiration linked phosphorylation involves membrane-bound enzymes and transmembrane gradient of protons and requires oxygen
what are enzymes?
- biological catalysts that accelerate the rate of chemical reactions
- creates new pathway for the reactions by lowering the activation energy
- don’t affect Gibbs free energy
what are cofactors?
non-protein molecules necessary for enzyme activity
what are coenzymes/cosubstrates?
have loose association with their enzyme and diffuse between enzymes carrying electrons
what are prosthetic groups?
- non protein cofactors that is covalently bonded to the enzyme
- not released as part of the reaction
- acts as a temporary store for electrons or intermediates
how doe redox reactions and coenzymes/prosthetic groups interlink?
- major redox coenzymes/prosthetic groups involved in transduction of energy from dietary foods to ATP: NAD+/FAD/FMN
- electrons are transferred from dietary material to these carriers —> coenzymes are reduced
- in each case 2 electrons are transferred but the number of H+ moved varies
rowdies nicotinamide adenine dinucleate (NAD+) work?
- NAD+ and NADP+ accept pairs of electrons to form NADH or NADPH
- it is the nicotinamide that is the functional part of the molecule
how are the redox coenzymes re-oxidated?
- recycling NADH and FADH2 via the respiratory chain in the mitochondria
- this is coupled to ATP synthesis: process of oxidative phosphorylation
what are the 2 possible fates of pyruvate?
- under aerobic conditions: oxidation and complete degradation
- in hypoxic conditions: it can be reduced to lactate
in aerobic conditions describe the one fate of pyruvate
- conversion to acetyl-CoA for oxidation and complete degradation
- in the mitochondria
- glycolysis occurs in the cytosol (can occur in the presence or absence of oxygen)
- —-> pyruvate is transported into the mitochondria for complete oxidation
how is pyruvate transported into the mitochondria?
- occurs via a specific carrier protein embedded in the mitochondria membrane in aerobic conditions
- pyruvate undergoes oxidative phosphorylation by the pyruvate dehydrogenase complex to form acetyl CoA: pyruvate + CoA + NAD+ —–> acetyl CoA + CO2 + NADH + H+
- reaction is irreversible and is the link between glycolysis and the citric acid cycle
what are the 9 intermediates of TCA cycle?
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1) Acetyl CoA
2) citrate
3) Isocitrate
4) a-ketoglutarate
5) succinyl CoA
6) succinate
7) fumarate
8) malate
9) oxaloacetate
how is the TCA cycle regulated?
flow of carbon atoms from pyruvate into and through the TCA cycle is tightly regulated at 2 levels:
1) conversions of pyruvate to acetyl-CoA
2) entry of acetyl-CoA into theTCA cycle
what are the products of glycolysis and the TCA cycle?
- glycolysis: pyruvate and NADH
- TCA cycle: 3 NADH, 1 FADH2, 1 GTP (ATP)
what are the 2 shuttles that transfers electrons from NADH into the mitochondria?
1) glycerol-3-phosphate shuttle especially prevalent in brain and muscle
2) malate-aspartate shuttle in liver and heart
*both shuttles act to regenerate NAD+ and make 1.5 or 2.5 moles of ATP
