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Kaplan: Biochemistry Part I > Chapter 12: Glycolysis and Pyruvate Dehydrogenase > Flashcards

Chapter 12: Glycolysis and Pyruvate Dehydrogenase Flashcards

1
Q

Name the complex forms of which most of our food is found in?

A

forms such as starch (amylose and amylopectin) and the disaccharides sucrose and lactose

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2
Q

What enzyme in the mouth starts breakdown of starch?

A

salivary amylase randomly hydrolyses the starch polymers to dextrins

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3
Q

In the intestines dextrins are hydrolyzed to what disaccharides?

A

maltose and isomaltose

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4
Q

Maltase cleaves maltose into what monosaccharides?

A

2 glucoses

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5
Q

Isomaltase cleaves isomaltose to what monosaccharides?

A

2 glucoses

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6
Q

Lactase cleaves lactose to what monosaccharides?

A

glucose and galactose

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7
Q

Sucrase cleaves sucrose to what monosaccharides?

A

glucose and fructose

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8
Q

What transporter takes up glucose into the mucosal cells?

A

GLUT

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9
Q

What is the normal glucose concentration in peripheral blood?

A

4-6 mM (70-110 mg/dL)

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10
Q

In the pancreas what serves as the glucose sensors?

A

GLUT 2 along with glucokinase

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11
Q

GLUT 4 translocation to the cell membrane in skeletal muscle is stimulated by exercise. This effect, is independent of insulin and involves what enzyme?

A

5’AMP activated kinase

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12
Q

What tissues is GLUT 1 found in?

A

Most tissue (brain, red cells)

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13
Q

What tissues is GLUT 2 found in?

A

Liver and pancreatic B-cells

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14
Q

What tissues is GLUT 3 found in?

A

Most tissues

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14
Q

What tissues is GLUT 4 found in?

A

skeletal muscle and adipose tissue

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14
Q

Which GLUT receptor has insulin-stimulated glucose uptake, stimulated by exercise in the skeletal muscle

A

GLUT 4

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14
Q

Insulin secretion by pancreatic B-cells is biphasic. What is meant by this statement?

A

glucose stimulates the first phase (within 15 minutes) with release of preformed insulin. The second phase (several hours) involves insulin synthesis at the gene level.

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14
Q

What is the rate limiting enzyme and main control point of glycolysis?

A

PFK-1

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14
Q

Which has the higher Km glucokinase or hexokinase

A

glucokinase

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14
Q

Where is glucokinase primarily found?

A

in hepatocytes and pancreatic B-cells along with GLUT-2, acts as the glucose sensor

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14
Q

Insulin stimulates and glucagon inhibits PFK-1 in hepatocytes by an indirect mechanism involving what?

A

PFK-2 and fructose 2,6 bisphosphate (F2,6-BP)

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14
Q

How does insulin activate PFK-2?

A

activates it via the tyrosine kinase receptor and activation of phosphatases, which converts a tiny amount of fructose 6- phosphate to fructose 2,6 bisphosphate (F2,6-BP) which in turn activates PFK-1 leading to stimulation of glycolysis

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14
Q

How does glucagon inhibit PFK 2?

A

via cAMP dependent protein kinase A lowering F2,6-BP and thereby inhibiting PFK-1

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14
Q

How can arsenate lead to death?

A

arsenate inhibits the conversion of glyceraldehyde 3-phosphate to 1,3-bisphosphoglycerate by mimicking phosphate in the reaction. The arsenate-containing product is water labile enabling glycolysis to proceed but resulting in no ATP production

14
Q

Near complete deficiency of glucokinase activity is associated with what condition?

A

neonatal type 1 diabetes.

15
Q

Mutations which increase the Km of glucokinase can cause what condition/ symptoms?

A

decreasing the affinity for glucose are associated with some cases of maturity-onset diabetes of the young (MODY)

hypoinsulinemia and hyperglycemia

16
Q

Mutations which decrease the Km of glucokinase (increasing the affinity for glucose)?

A

hyperinsulinemia and hypoglycemia

17
Q

What does DHAP stand for?

A

dihydroxyacetone phosphate

18
Q

What is the function of DHAP?

A

used in liver and adipose tissue for triglyceride synthesis

electron shuttle metabolite

19
Q

3 enzymes in the glycolysis pathway catalyze reactions that are irreversible. What are they?

A

glucokinase/hexokinase
PFK-1
pyruvate kinase

20
Q

What is C-peptide?

A

a short polypeptide that connects the A chain to the B[chain in the proinsulin molecule. It is removed after proinsulin is packaged into vesicles in the Golgi

21
Q

How much energy products are produced by anaerobic glycolysis?

A

2 ATP/glucose

22
Q

How much energy is produced from aerobic glycolysis? (in cytoplasm)

A

2ATP/glucose plus 2 NADH/glucose

23
Q

Cytoplasmic NADH oxidized using the malate shuttle produces mitochondrial NADH and yields how much ATP?

A

3ATP by oxidative phosphorylation

24
Q

Cytoplasmic NADH oxidized by the glycerol phosphate shuttle produces mitochondrial FADH2 and yields approximately how much ATP?

A

2 ATP by oxidative phosphorylation

25
Q

In RBC anaerobic glycolysis represents the only pathway for ATP production yielding how much ATP?

A

2 ATP/glucose

26
Q

Draw out the glycolysis pathway.

A

Draw out diagram

27
Q

What is the enzyme found in the erythrocytes that produces 2,3 BPG from 1,3 BPG in glycolysis?

A

Biphosphoglycerate mutase

28
Q

Which chains does 2,3 BPG bind to in HbA?

A

2,3 BPG binds to the β-chains of HbA

29
Q

Why can 2,3 BPG not bind to HbF well?

A

HbF has a higher affinity for O2 and only binds to β subunit which isn’t found in HbF

30
Q

What are the chain (subunits) that comprise HbF?

A

α2γ2

31
Q

What is the second most common genetic deficiency that causes hemolytic anemia?

A

pyruvate kinase deficiency

32
Q

What is the most common genetic deficiency which causes hemolytic anemia?

A

G6PDH (glucose 6-phosphate dehydrogenase)

33
Q

What are the characteristics of pyruvate kinase deficiency?

A
  1. chronic hemolysis
  2. increased 2,3 BPG and therefore a lower than normal O2 affinity of HbA
  3. Absence of Heinz bodies (Heinz bodies are more characteristic of G6PD deficiency
34
Q

Why does pk deficiency in the RBC lead to hemolysis?

A

anaerobic glycolysis is only way for RBC to produce ATP because no mitochondria

Decrease in ATP causes erythrocyte to lose its characteristic biconcave shape and signals its destruction in spleen

Decreased ion pumping by Na+/K+ ATPase results in loss of ion balance and causes osmotic fragility, leading to swelling and lysis

35
Q

Why is transfused blood not as good at delivering O2 to peripheral tissues?

A

has lower than expected 2,3 BPG

36
Q

What is the meaning of P50?

A

Pressure @ which hemoglobin is 50% saturated

37
Q

What are conditions that create a Bohr effect?

A

anything that shifts the O2/Hb curve to the right

Inc. CO2
Inc. H+
Inc. T
Inc. 2,3 BPG
Inc P50

38
Q

What is a the meaning of shift to the right on the O2/Hb dissociation curve?

A

means there is a dec. affinity for O2(Hb) bond and therefore more unloading of O2

39
Q

What are conditions that create a haldane effect?

A

dec. CO2
dec. H+
dec. 2,3 BPG
dec. T
dec P50

40
Q

What is the meaning of a left shift on the O2/Hb dissociation curve?

A

means higher affinity of Hb for O2 and less unloading of O2

41
Q

Be able to draw out the flow in Galactose metabolism.

A

Draw out diagram

42
Q

What are the symptoms of lactase deficiency after ingestion of lactose (milk products)?

A

diarrhea
bloating
cramps

43
Q

What are the symptoms of galactokinase deficiency?

A

cataracts early in life

44
Q

What are the symptoms of Gal 1-P uridyltransferase deficiency?

A
  • cataracts early in life
  • vomiting, diarrhea following lactose ingestion
  • lethargy
  • liver damage, hyperbilirubinemia
  • intellectual disability
45
Q

Can administration of galactose during hypoglycemia be used to increase blood glucose?

A

yes

46
Q

In the well-fed state, galactose can enter glycolysis and lead to storage of what?

A

glycogen storage

47
Q

Where is lactase present?

A

associated with brush border membrane of the small intestine

Kaplan: Biochemistry Part I (27 decks)

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