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SFM Quiz 1 > Carbohydrate Metabolism > Flashcards

Carbohydrate Metabolism Flashcards

1
Q

What are the products of glycolysis?

A

2 ATP, 2 NADH, and 2 Pyruvate

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2
Q

How is GLUT 4 activated?

A

Insulin binds to insulin receptor in membrane, activating vesicles containing GLUT4 to bind to membrane and let glucose in.

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3
Q

What is the rate limiting enzyme in glycolysis?

A

Phosphofructokinase-1 (PFK-1)

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4
Q

What are the 3 irreversible phosphorylation steps of glycolysis?

A
  • Hexokinase/Glucokinase
  • Phosphofructokinase-1
  • Pyruvate kinase
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5
Q

What is hexokinase (HK) inhibited by?

A

G6P, its product

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6
Q

How is glucokinase (GK) inhibited?

A

F6P promotes relocation to the nucleus where it cannot act on glycolysis. High glucose levels relocate it out of the nucleus.

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7
Q

What is PFK-2’s role in glycolysis regulation?

A

When recently fed, it will create F2,6BP from F6P which will activate PFK-1.

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8
Q

What is Tarui disease?

A

Deficiency in PFK-1.

Symptoms: muscle cramps/weakness, jaundice, hemolytic anemia

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9
Q

What is cAMP’s role in pyruvate kinase (PK) regulation?

A

High glucagon increases concentration of cAMP which phosphorylates and inhibits PK.

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10
Q

What are the clinical markers for hemolytic anemia?

A

Elevated lactate dehydrogenase and unconjugated bilirubin because these are released from RBCs when they are lysed.

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11
Q

What is Fanconi-Bickel syndrome?

A

Mutation in GLUT 2 transporter. Unable to take up glucose, fructose, and galactose in liver/pancreas.

Symptoms: failure to thrive, hepatomegaly, abdominal bloating, rickets.

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12
Q

What are the precursor molecules for gluconeogenesis?

A

Fructose, galactose, glycogen, glycerol, propionate, lactate, alanine, amino acids

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13
Q

What is the rate limiting enzyme of gluconeogenesis?

A

Fructose 1,6-biphosphatase

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14
Q

What enzyme in gluconeogenesis is only found in the liver, kidney’s, and pancreas?

A

Glucose 6-phosphatase

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15
Q

What enzymes in gluconeogenesis “bypass” the irreversible steps of glycolysis?

A
  • Pyruvate carboxylase and PEP carboxykinase bypass pyruvate kinase
  • Fructose 1,6 biphosphatase bypasses PFK-1
  • Glucose 6-phosphatase bypasses hexokinase/glucokinase
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16
Q

What is the cofactor for pyruvate carboxylase?

A

Biotin

17
Q

How is G6P converted to glucose?

A

G6P is brought to glucose 6-phosphatase, which is located in the lumen of the ER (liver, kidneys, and pancreas only). Glucose 6-phosphatase consists of a catalytic unit, an antiporter, and a GLUT7 so glucose and be transferred back to the cytoplasm.

18
Q

What is F1,6BP deficiency?

A

A deficiency in the rate-limiting enzyme of gluconeogenesis.

Symptoms: hypoglycemia, lactic acidosis, ketosis

19
Q

What is Von Gierke disease/GSD1a?

A

Deficiency in glucose 6-phosphatase, the last step of gluconeogenesis.

Symptoms: fasting hypoglycemia, lactic acidosis, hepatomegaly due to buildup of glycogen, hyperlipidemia

20
Q

Describe the Polyol pathway.

A

It is the process by which glucose is converted to fructose. First, glucose is reduced to sorbitol by Aldose reductase. Then, sorbitol is oxidized to fructose by Sorbitol dehydrogenase.

21
Q

What leads to sorbitol accumulation and what are the symptoms?

A

Occurs in cells that lack sorbitol dehydrogenase (Polyol pathway).

Symptoms: swelling, retinopathy, cataracts

22
Q

How is fructose metabolism different than glucose metabolism?

A

Fructose metabolism is faster and bypasses the rate limited step (PFK-1) of glycolysis. Can lead to excess fatty acid formation.

23
Q

What is the rate-limited enzyme of galactose metabolism?

A

Glucose 1P uridyltransferase (GALT)

24
Q

What are the two main types of Galactosemia and their associated symptoms?

A
  1. Deficiency in GALT (classic galactosemia) leads to accumulation of galactitol. Symptoms: failure to thrive, liver failure.
  2. Deficiency in galactokinase (nonclassical galactosemia) leads to the accumulation of galactitol. Symptoms: cataracts in early infancy.
25
Q

What is the role of glutathione?

A

Antioxidant, detoxifies H2O2

26
Q

Where in the body is there high demand for PPP?

A

Lactating mammary glands, lung/liver tissue, and phagocytic cells.

27
Q

On what end is glycogen both degraded and extended?

A

From the non-reducing end

28
Q

What protein is attached to the reducing end of glycogen?

A

Glycogenin

29
Q

Describe G6PD deficiency.

A

PPP cannot proceed, leading to low NADPH levels. Common in African population.

Symptoms: hemolytic anemia.

30
Q

What does Glycogen phosphorylase (GP) use as a cofactor?

A

Pyridoxal phosphate (vitamin B6)

31
Q

How is glycogen synthase and glycogen phosphorylase regulated?

A

Glycogen synthase is activated in the dephosphorylated form. Glycogen phosphorylase is activated in the phosphorylated form.

32
Q

Describe how insulin activates glycogen synthesis.

A

Insulin binds to insulin receptor which activates PKB and translocates GLUT 4 to the plasma membrane. PKB activates PP1 and inactivates GSK3.

33
Q

What is GSD 0?

A

Deficiency in glycogen synthase. Rely on glucose in diet.

34
Q

What is Pompe disease/GSD II?

A

Deficiency in Acid Maltase aka acid alpha-glucosidase. Impairs lysosomal glycogenolysis, resulting in accumulation of glycogen in lysosomes.

35
Q

What is Cori Disease/GSD III?

A

Deficiency in alpha-1,6-glucosidase (debranching enzyme). Leads to glycogen molecules with large number of short branches.

36
Q

What is Andersen disease/GSD IV?

A

Deficiency in glucosyl (4:6) transferase (branching enzyme). Patients have long glycogen chains with fewer branches. Death by 5 years of age.

37
Q

What is McArdle disease?

A

Deficiency in muscle glycogen phosphorylase. Unable to supply muscles with enough glucose.

38
Q

What is Hers disease/GSD VI?

A

Deficiency in liver glycogen phosphorylase. Leads to hepatomegaly.

39
Q

What does glycogen phosphorylase use as its cofactor?

A

Pyridoxal phosphate (vitamin B6)

SFM Quiz 1 (8 decks)

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