cellular respiration

Question 1

what is aerobic respiration?

Answer 1

1. catabolic reaction, exergonic reaction since it releases energy
2. C6H12O6 + 6O2 -> 6CO2 + 6H2O + 30-32ATP
3. glycolysis -> link reaction and krebs cycle -> oxidative phosphorylation/electron transport chain
4. produces 30-32 ATP

Question 2

what is glycolysis?

Answer 2

1. occurs in the cytosol
2. breaks 1 glucose (6-carbon) molecule into two 3-carbon pyruvates. coenzyme NAD+ picks up two e- and a proton, and turns into NADH. when NADH releases charged particles, it also releases energy that can be used to synthesise ATP. production of 2 ATP per glucose
   glucose + 2 ADP + 2Pi + 2NAD+ => 2x3c pyruvates, 2NADH, 2ATP
3. anaerobic process.

Question 3

what is the link reaction?

Answer 3

the conversion of 1 3C pyruvate into 1 acetylCoA (2C) ready for entry into the Krebs cycle. this occurs in the mitochondrial matrix and produces 1CO2 per pyruvate (therefore 2CO2 per glucose)
2 pyruvate + 2 CoA + 2 NAD+ -> 2 acetylCoA + 2CO2 + 2 NADH

Question 4

what is the Krebs cycle?

Answer 4

1. each acetyl CoA molecule is broken down to produce 2 CO2, 1 ATP, 3 NADH, 1 FADH2.
2. FAD carries H+ ions and electrons that are released in the breakdown of acetyl CoA, and is converted into FADH2. when FADH2 reverts to FAD, it releases energy used to synthesise ATP.
3. 2 acetyl CoA + 6 NAD+ + 2FAD + 2 ADP + 2Pi => 4CO2 + 6 NADH + 2 FADH2 + 2 ATP.
4. produces many electron carriers like NADH and FADH2 that are used up by the ETC to produce ATP.
5. happens in the mitochondrial matrix, it is an oxygen dependent process (aerobic).

Question 5

what is oxidative phosphorylation/ electron transport chain?

Answer 5

1. where electrons donated by electron carriers like NADH and FADH2 are used to power proton (H+) pumps (transmembrane proteins) in the inner mitochondrial membrane (cristae) to help them pump H+ ions across the membrane into the intermembrane space
2. this creates a chemiosmotic gradient across the membrane. H+ ions therefore diffuse down their conc. gradient through the ATP synthase in the membrane to help produce 26-28 ATP from 26-28 ADP + Pi
3. oxygen acts as the final electron acceptor in the ETC and combines with H+ ions to form stable H2O.
   - aerobic, krebs cycle is dependent on the functioning of the ETC
   - produces the highest number of ATP molecules