B MCAT - Metabolism

Question 1

Pathway from glucose to electron transport chain

Answer 1

Glucose undergoes glycolysis in cytoplasm to make pyruvate.
Pyruvate undergoes pyruvate dehydrogenase pathway (enzyme PDH) in mitochondrial matrix to make acetyl Co-A, which is used in the citric acid cycle to make ATP, plus NADH and FADH2 which enter the electron transport chain at complexes I and II, respectively.

Question 2

Pathway from fatty acids to the electron transport chain

Answer 2

Fatty acids are broken down in mitochondria matrix via beta oxidation to acetyl CoA, which is used in the citric acid cycle to make ATP, plus NADH and FADH2 which enter the electron transport chain at complexes I and II, respectively.

Question 3

Enzymes in the 3 irreversible steps of glycolysis

Answer 3

In step 1, hexokinase.

In step 3, phosphofructokinase (PFK-1). Rate-limiting step.

In step 10, pyruvate kinase.

Operate on negative feedback.

Question 4

Rate-limiting enzyme of beta oxidation

Answer 4

malonyl-CoA

Question 5

Indicators of energy deficiency

Answer 5

Ca+
ADP
NAD+

Question 6

Glycolysis Inputs + Outputs

Answer 6

INPUTS:
1 molecule glucose (6 C chain)
2 NAD+
2 ATP (at steps 1 and 3)
2P

OUTPUTS:
2 pyruvate (3 C each)
2 NADH
4 ATP (at steps 7 and 10)

(4-2=2 net ATP)