Review 1: Glycolysis

Question 1

What energy source does the skeletal muscle use at rest? exertion?

Answer 1

fatty acids

gluocse

Question 2

What energy source does the heart use?

Answer 2

fatty acids

Question 3

What is the energy source for the brain during starvation?

Answer 3

ketone bodies

Question 4

How many grams of glucose does the brain need per day?

Answer 4

120

Question 5

How many grams of glucose does skeletal muscle need per day?

Answer 5

40

Question 6

What is the normal min of fasting blood glucose?

Answer 6

60mg/dL

Question 7

What enzyme(s) convert glucose to glucose 6-phosphate?

Answer 7

hexokinase/glucokinase

Question 8

What enzyme converts fructose 6-phosphate to fructose 1,6-bisphosphate?

Answer 8

PFK1 (phosphofructokinase)

Question 9

When is NAD+ required in glycolysis?

Answer 9

During the conversion of glyceraldehyde 3-phosphate to bisphosphate (missing this and glycolysis stalls at priming stagE and goes towards lactate acid production)

Question 10

What enzyme converts PEP (phosphoenolpyruvate) to pyruvate?

Answer 10

pyruvate kinase

Question 11

What enzyme converts pyruvate into oxaloacetate?

Answer 11

pyruvate carboxylase

Question 12

Where is glucokinase found?

Answer 12

liver and pancreas

Question 13

Between hexokinase and glucokinase, which has greater glucose affinity?

Answer 13

hexokinase (lower Km)

Question 14

Which enzyme is insulin inducible, hexokinase or glucokinase?

Answer 14

glucokinase

Question 15

What inhibits hexokinase?

Answer 15

its product, glucose 6-phosphate

Question 16

What inhibits glucokinase?

Answer 16

location - inhibited in the nucleus, active in the cytosol

Question 17

What are possible fates of pyruvate?

Answer 17

1) Alanine (transamination)
2) Oxaloacetate (pyruvate carboxylase)
3) Lactate (lactate dehydrogenase)
4) TCA cycle (pyruvate dehydrogenase)

Question 18

What are the clinical signs of PDH deficiency?

Answer 18

increases in circulatory pyruvate and lactate

microcephaly, poor muscle coordination

Question 19

What are the clinical signs of pyruvate carboxylase deficiency?

Answer 19

increases in blood alanine, lactate, pyruvate

developmental delay, seizures, metabolic acidosis

Question 20

What must be regenerated to maintain glycolytic flux?

Answer 20

NAD+

Question 21

What reaction in glycolysis uses NAD+?

Answer 21

glyceraldehyde 3-P dehydrogenase reaction

Question 22

How does anaerobic respiration replenish the NAD+?

Answer 22

through a reduction reaction leading to lactate or ethanol production

Question 23

How does aerobic respiration replace NAD+?

Answer 23

metabolite shuttle system

Question 24

True or false: NADH can cross the mitochondrial membrane

Answer 24

FALSE (it cannot)

Question 25

Name 3 ways NAD+ can be regenerated:

Answer 25

1) Lactate dehydrogenase 2) Malate-aspartate shuttle 3) Glycerol-phosphate shuttle

Question 26

Which enzyme is a multienzmye complex (E1, E2, E3) that catalyzes the conversion of pyruvate and coenzyme A to acetyl CoA?

Answer 26

Pyruvate dehydrogenase (PDH)

Question 27

What vitamins are required for PDH function?

Answer 27

B1, B2, B3, and B5

Question 28

What limitations do patients with Lactate Dehydrogenase A Deficiency face?

Answer 28

exercise (inability to utilize glycolysis to produce ATP needed for muscle contraction under anaerobic conditions)

Question 29

What intermediate specifically suffers with lactate dehydrogenase A deficiency?

Answer 29

the level of NAD+ (becomes limiting during exercise so flux thru glyceraldehyde 3-P dehydrogenase reaction is inhibited)

Question 30

What is the net ATP gain in glycolysis?

Answer 30

2 ATP

Question 31

How many ATP are consumed during glycolysis?

Answer 31

2 (but 4 are produced - 2 per pyruvate)

Question 32

Low levels of cellular NADH favor ___________ (aerobic/anaerobic respiration)

Answer 32

aerobic (decrease lactate formation)

Question 33

Oxygen is required for reoxidation of NADH in the mitochondria or cytosol?

Answer 33

BOTH

Question 34

During galactosemia, what two things build up?

Answer 34

galactitol and galactose 1-phosphate

Question 35

What causes galactosemia?

Answer 35

deficiency of 1) galactose 1-phosphate uridyltransferase (classic and most severe) 2) galactokinase

Question 36

What step converts galactose to galactitol?

Answer 36

oxidation of NADPH to NADP+

Question 37

What enzyme converts galactose to galactose 1-P?

Answer 37

galactokinase

Question 38

What enzyme converts galactose 1-P to glucose 1-P?

Answer 38

gal-1-P uridyltransferase

Question 39

What are some clinical features of galactosemia?

Answer 39

cataracts

Question 40

What is aldolase B and why is it important?

Answer 40

Fructose-bisphosphate aldolase B plays a role in glycolysis and gluconeogenesis deficiency in this enzyme leads to fructose intolerance

Question 41

Deficiency of ___________ __ leads to fructose intolerance

Answer 41

aldolase B

Question 42

What does fructose accumulation lead to?

Answer 42

high uric acid and high lactic acid