Respiration Flashcards
4 stages of aerobic respiration
Glycolysis - splitting of glucose to two pyruvate
Link reaction - pyruvate forms acetylcoenzyme A (2C).
Krebs cycle - acetylecoenzyme A introduced into cycle that yields ATP and reduced NAD and FAD.
Oxidative phosphorylation - electron transfer chain using electrons donated by NADH and FADH
Glycolysis
1) Glucose phosphorylated to hexose phosphate by hydrolysis of 2 ATP.
2) Hexose phosphate split into 2 3C molecules (triose phosphate).
3) Each triose phosphate is oxidised (removal of H) and NAD is reduced.
4) Enzyme controlled reactions convert triose phosphate into pyruvate and 2 molecules of ATP regenerated from ADP each.
Energy yield from glycolysis
2 ATP (4 produced but 2 used)
2 reduced NAD
2 pyruvate
Where does glycolysis take place
Cytoplasm
Link reaction
Pyruvate oxidised to acetate (2C) by loss of CO2 and 2H. These are accepted by NAD to form NADH.
Acetate combines with coenzyme A to form acetylcoenzyme A. (1 for each pyruvate).
Krebs cycle
Acetylecoenzyme A combines with 4C compound to form 6C molecule.
Then loses 2 CO2 and some H (forming reduced NAD and reduced FAD) to give 4C molecule and single ATP (sub level phos).
4C compound reenters cycle.
Products of link reaction and Krebs cycle
Reduced NAD and FAD for oxidative phos.
1 ATP.
3 CO2.
(per 1 pyruvate).
Significance of Krebs cycle
Breaks down pyruvate to CO2.
Produces H atoms that are then carried by NAD to electron transfer chain for oxidative phos to produce ATP.
Regenerates 4C molecule that combines with acetylecoenzyme A.
Source of intermediate compounds in manufacture of fatty acids, amino acids, chlorophyll.
Where does link and Krebs take place
Mitochondrial matrix
Oxidative phosphorylation
Hydrogen atoms produced during glycolysis and Krebs combine with NAD and FAD.
They donate electrons of hydrogen atoms they carry to first molecule in ETC.
Electrons pass along chain of electron transfer carrier molecules in series of redox reactions, energy released causes active transport of protons across inner mitochondrial membrane from the mitochondrial matrix into inter-membrane space.
Protons accumulate in this space before they diffuse back to matrix via ATP synthase channels.
Electrons finally are accepted by oxygen and combine with H to form water.
Why is energy released in stages by electrons being transferred in series of transfer molecules, slightly lower level each time?
More energy transferred at once = more heat = more waste, means energy used more usefully.
Respiration of lipids
Hydrolysed to glycerol and fatty acids.
Glycerol phosphorylated and converted to triose phosphate for glycolysis.
Fatty acids turned into many acetyl coenzyme A.
Lipids high energy due to many H atoms that can be used in oxidative phosphorylated.
Respiration of protein
Hydrolysed to amino acids.
Deaminated and enter respiratory pathway depending on how many carbons
Why do we respire anaerobically
When no oxygen, NADH accumulates and must be used.
Anaerobic respiration
Pyruvate takes 2 hydrogen atoms from NADH produced in glycolysis to form lactate.
Replenishes NAD
