Chapter 27

Question 1

Glycolysis?

Answer 1

metabolism of 6 carbon glucose to two 3 carbon pyruvate (C3H3O3) in cytoplasm of almost every cell in the body

Question 2

What are the two fates of pyruvate in skeletal muscle?

Answer 2

1. oxidation in mitochondria

2. reduction to lactate in cytoplasm in anaerobic glycolysis

Question 3

Anaerobic glycolysis?

Answer 3

• incomplete breakdown of 6 carbon glucose to two 3 carbon lactates (C3H5O3) without use of oxygen in cytoplasm
• rapid- fast resynthesis of ATP

Question 4

What is the additional step in anaerobic glycolysis compared to glycolysis?

Answer 4

reduction of pyruvate to lactate

Question 5

Glycolytic muscle fibers?

Answer 5

type IIa and IIx b/c of their use of anaerobic glycolysis for energy

Question 6

What are the steps of phase 1 (energy consuming) of anaerobic glycolysis?

Answer 6

1. Glucose is transported across the cell membrane by GLUT 4
2. Glucose is phosphorylated to G6P by hexokinase(muscle) and glucokinase (liver), irreversible step, one ATP is used, ADP produced
3. G6P either undergoes Glycolysis or Glycogenesis
4. G6P becomes F6P by phosphoglucoisomerase
5. F6P is phosphorylated to become F16BP by PFK, ATP is used, ADP produced
6. F16BP is converted to two 3 carbon molecules: glyceraldehyde-3-phosphate and dihydroxy acetone phosphate by the enzymes Aldolase and Triose-phosphate isomerase

Question 7

What are the steps of phase 2 (energy yielding) of anaerobic glycolysis responsible for?

Answer 7

• result in the synthesis of two ATP from each three carbon molecule, so four in total because phase 2 occurs twice
• substrate level phosphorylation- phosphates necessary to resynthesize ATP from ADP come directly from substrates in the metabolic pathway

Question 8

When the energy substrate is blood glucose, what is the net ATP resynthesis?

Answer 8

2 ATP used in phase 1
4 ATP resynthesized in phase 2

Net = 2 ATP

Question 9

What is the net ATP when anaerobic glycolysis begins in with muscle glycogen?

Answer 9

1 ATP used in phase 1
4 ATP gained in phase 2

Net = 3 ATP

phosphorylation of glucose to G6P is bypassed conserving 1 ATP

Question 10

What are the two carrier molecules for hydrogens and electrons removed from energy substrates and intermediates?

Answer 10

NAD and FAD

Question 11

In anaerobic glycolysis, the hydrogens removed from glyceraldehyde-3-phosphate are transported by what? What does it form?

Answer 11

• NAD transports and donates H+ to pyruvate to form lactate
• pyruvate is reduced as it accepts 2 H+
• NADH + H is oxidized to NAD because it loses 2 H+

Question 12

Reduced?

Answer 12

accept H+, gain electrons, or lose oxygen

Question 13

Oxidized?

Answer 13

lose H+, lose electrons, or accept oxygen

Question 14

Why is the final step to reduce pyruvate to lactate important?

Answer 14

NADH is oxidized to become NAD which is recycled back to step 6

Question 15

Hexokinase?

Answer 15

catalyzes phosphorylation of glucose

Question 16

Phosphofructokinase (PFK)?

Answer 16

rate limiting enzyme, catalyzes phosphorylation of F6P

Question 17

Lactate Dehydrogenase (LDH)?

Answer 17

catalyzes reduction of pyruvate to lactate

Question 18

What is the net metabolic equation from the resynthesis of 2 ATP from blood glucose?

Answer 18

C6H12O6 + 2Pi +2ADP -> 2C3H5O3+2ATP+2H

glucose) (lactate

Question 19

How long can anaerobic glycolysis sustain maximal exercise?

Answer 19

1-3 minutes

Question 20

What factors determine the path that pyruvate takes?

Answer 20

1. rate of pyruvate formation
2. activity of lactate dehyrogenase (reduces pyruvate to lactate)
3. activity of pyruvate dehydrogenase (converts pyruvate to acetyl CoA in mitochondria)
4. redox potential in the cell (ratio NAD/NADH)
5. oxidative capacity of the cell
6. availability of oxygen in cell to be used for oxidative phosphorylation

Question 21

What happens to the efficiency of anaerobic glycolysis as intensity of exercise increases?

Answer 21

rate of ATP resynthesis increases but efficiency decreases (about 2% of total 686 kcal of potential energy in glucose from ATP)