Chapter 9.2

Question 1

Can all cells carry out glycolysis

Answer 1

• yes

- >red blood cells depend on glycolysis for energy because they lack mitochondria

Question 2

What is the end result of glycolysis

Answer 2

-convert glucose into two pyruvate molecules

Question 3

Contrast hexokinase and glucokinase

Answer 3

Hexokinase

• > present in most tissues
• > low Km(reaches maximum velocity at low [glucose])
• > inhibited by glucose 6-phosphate

Glucokinase

• > present in hepatocytes and pancreasing B-islet cells
• > high Km(acts on glucose proportionally to its concentration)
• > induced by insulin in hepatocytes

Question 4

What is the rate limiting for glycolysis

Answer 4

-phosphofructokinase 1

Question 5

How does ATP, citrate and AMP relate to PFK-1?

Answer 5

• high levels of ATP and citrate inhibit PFK-1

- high levels of AMP activate PFK-1

Question 6

How does insulin, and glucagon relate to PFK-1?

Answer 6

-insulin activates PFK-1 and glucagon inhibits it

Question 7

What is the role of PFK-2?

Answer 7

• converts fructose-6 phosphate to fructose 2,6-biphosphate

- even with high levels of ATP, PFK 2 allows for the continued activation of PFK 1

Question 8

How does fructose 1,6-biphosphate relate to pyruvate kinase

Answer 8

• it results in feed-forward reaction

- >so the product formation of fructose 1,6-biphosphate stimulates pyruvate kinase

Question 9

What are the three irreversible enzymes of glycolysis

Answer 9

• glucokinase or hexokinase
• PFK-1
• Pyruvate kinaase

Question 10

When does fermentation occur? Relate it to oxygen levels

Answer 10

-in the absence of oxygen, fermentation will occur

Question 11

How does fermentation allow for glycolysis to keep going

Answer 11

• it oxidizes NADH to NAD+
• > glycolysis needs NAD+ to continue working
• > so fermentation provides glycolysis with that NAD+
• note when NADH is oxidized to NAD+
• > pyruvate is reduced to lactate by lactate dehydrogenase

Question 12

How does fermentation differ in yeast cells

Answer 12

• in yeast cells instead of producing lactate, pyruvate is reduced to produce carbon dioxide and ethanol
• again NAD+ is replenished

Question 13

What is DHAP used for in hepatic and adipose tissue

Answer 13

• it is used for triacylglycerol synthesis
• DHAP is formed from 1,6-biphosphate
• > it is then isomerized to glycerol 3-phosphate which can then be converted to glycerol
• > glycerol is the backbone of triacylglycerol