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5.2.2 Aerobic Respiration (Oxidative phosphorylation (Products: (28 x ATP,…
5.2.2 Aerobic Respiration
Glycolysis
Phosphorylation
glucose converted to hexose biphosphate
two ATP molecules are hydrolysed (activation energy)
Splitting of hexose biphosphate
two triose phosphate molecules produced
Further oxidation to pyruvate
triose phosphate to pyruvate
dehydrogenase enzymes (with NAD) remove hydrogens from triose phosphate
two molecules of NAD accept hydrogen atoms so is reduced
four molecules of ATP are produced
Occurs in cytoplasm of cell
First stage of respiration; a ten stage process converting glucose to pyruvate (anaerobic)
Used per molecule of glucose:
1 x glucose molecule
2 x ATP molecules
2 x NAD
Products:
2 x NADH
(4 x ATP molecules)
net production of 2 x ATP molecules
2 x pyruvate molecules
Link reaction
occurs in mitochondrial matrix
Formation of Acetyl CoA by decarboxylation of pyruvate and reduction of NAD to NADH; aerobic
pyruvate transported into mitochondria via specific pyruvate H⁺ symport
carboxyl group of pyruvate is removed, and hydrogen; produces an acetyl group
acetyl group combines with CoA to become acetyl CoA
NAD is reduced
Used per molecule of glucose:
2 x pyruvate molecules
2 x NAD
2 x CoA
Products:
2 x NADH
2 x carbon dioxide
2 x acetyl CoA
Krebs cycle
occurs in mitochondrial matrix
Formation of citrate from acetyl group of acetyl CoA and oxaloacetate
Reconversion of citrate to oxaloacetate; aerobic
decarboxylation: removal of carboxyl group from a substrate molecule
dehydrogenation: removal of hydrogen atoms from a substrate molecule
substrate level phosphorylation: production of ATP from ADP and P during glycolysis and Krebs cycle
Used per molecule of glucose:
2 x acetyl CoA
Products:
6 x NADH
2 x FADH
4 x carbon dioxide
2 x ATP
Importance of coenymes
NAD
non protein
helps dehydrogenase enzymes to carry out oxidation; oxidises substrate molecules
reduced NAD (NADH) carries protons and electrons to cristae, to be used in oxidative phosphorylation; becomes re-oxidised to NAD to be reused
NADH produce 3 ATP each
FAD
FADH produce 2 ATP each
coenzyme A
need to accept hydrogen atoms released during oxidation
provide protons and electrons to electron transport chain
Oxidative phosphorylation
Formation of ATP using energy released in electron transport chain and in the presence of oxygen (aerobic)
occurs in mitochondria (cristae)
NADH and FADH are re-oxidised when they deliver their H atoms to electron transport chains
H atoms are split into protons and electrons
protons go in solution in mitochondrial matrix
electron carrier have a coenzyme that pumps protons from matrix to intermembrane space; use energy released tom electrons
proton gradient forms across membrane; protons accumulate in intermembrane space
protons diffuse through ATP synthase proton carriers; flow of protons causes conformational shape change in ATP so ADP and P is combined
iron ions can accept and donate ions
reduced when gain electrons (Fe²⁺)
oxidised when donating electron to next electron carrier (Fe³⁺)
Used per molecule of glucose:
6 x oxygen molecules
oxygen is final electron acceptor; combines with electrons and protons to form water
Products:
28 x ATP
6 x water molecules
Chemiosmotic theory
electron carriers: protein complexes arranged in electron transport chain; contain cofactor (non-protein haem group containing iron ion); oxido-reduction enzymes
chemiosmosis: flow of protons down concentration gradient across a membrane through a channel associated with ATP synthase
chemiosmotic potential: source of potential energy generated from proton gradients; aka proton motive force
protons diffuse through ATP synthase proton carriers; flow of protons causes conformational shape change in ATP so ADP and P is combined
Sammer Sheikh