Cellular Respiration: (Krebs Cycle)

Question 1

Krebs cycle uses what kind of respiration?

Answer 1

Aerobic cellular respiration.

Question 2

Glycolysis:

Answer 2

-by the end of glycolysis the cell has produced:
•2 ATP.
•2 NADH.
•2 H2O.
•2 pyruvate (C3) molecules.
-glycolysis is an anaerobic reaction, but under aerobic conditions, when O2 is present, cellular respiration moves from the cytoplasm into the mitochondrial matrix.

Question 3

Kreb’s cycle preparation overview:

Answer 3

•when O2 is available, pyruvate (3 carbons) enters the matrix of the mitochondria.
•a series of reactions yield (produce) carbon dioxide (1 carbon) and acetyl -CoA (2 carbons).
•NAD+ is reduced to NADH (which can make ATP via the ETC).

Question 4

Pyruvate oxidation:

Answer 4

•carbon dioxide is removed from each pyruvate (released as waste).
•the remaining C2 portions are oxidized by NAD+.
•in the process, each NAD+ molecule gains a hydrogen atom (NAD+ + 2e- + H+ —> NADH).
•the remaining C2 compound becomes an acetate group.
•the acetate group joins with a co-enzyme to form acetyl CoA (C2).
-goes to Krebs.

Question 5

Pyruvate oxidation (for 2 pyruvate):

Answer 5

-inputs:
•2 pyruvate.
•2 CoA.
•2 NAD+.
-outputs:
•2 CO2 (diffuse out as waste).
•2 acetyl CoA (goes to Krebs).
•2 NADH (goes to ETC).

Question 6

The Kreb’s cycle:

Answer 6

-also called “citric acid cycle”.
-takes place in the matrix of the mitochondria.
-it is cyclic because the product of the last step (oxaloacetate) is a reactant in the first step.

Question 7

Kreb’s cycle overview:

Answer 7

•acetyl-CoA enters the Kreb’s cycle by combining with a four-carbon compound (oxaloacetate).
•during the Kreb’s cycle, two carbon atoms are fully oxidized to carbon dioxide.
•NAD+ and FAD are reduced to NADH and FADH2.
•small amount of ATP is produced.

Question 8

Kreb’s cycle:

Answer 8

-the acetyl group (C2) carried by CoA combined with oxaloacetate (C4) this results in the formation of citrate (C6).
-CoA is released (used for next pyruvate).
-during one complete cycle (1acetyl CoA):
•3 NAD+ are reduced —> 3 NADH.
•1 FAD+ is reduced —> 1 FADH2.
•1 ADP and Pi are combined —> 1 ATP.
•2 CO2 molecules are produced (waste).

Question 9

Kreb’s cycle (2 turns for 2 pyruvates) (after oxidation so more like Acetyl CoA):

Answer 9

-inputs:
•2 acetyl CoA.
•6 NAD+.
•2 FAD+.
•2 ADP + 2 Pi.
-outputs:
•4 CO2.
•6 NADH.
•2 FADH2.
•2 ATP.

Question 10

Kreb’s cycle summary:

Answer 10

•by the end of the Kreb’s cycle:
•all 6 carbon atoms of glucose have been oxidized CO2 (released as waste).
•all that is left of the original glucose is free energy (ATP) and high energy NADH and FADH2.
•these molecules now go into stage 4 of the process (electron transport/chemiosmosis).

Question 11

CoA:

Answer 11

(Coenzyme A).