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BCH MEtabolism > Glycolysis > Flashcards

Glycolysis Flashcards

1
Q

family of glucose carrier proteins that transport glucose into the cell

A

GLUT

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2
Q

glucose transporter used by liver & pancreas

A

GLUT2

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3
Q

glucose transporter used by muscle & adipose

A

GLUT4

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4
Q

Which GLUT is sensitive to insulin

A

GLUT4

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5
Q

glucose transport is coupled with

A

Sodium

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6
Q

Glucose is trapped in the cell by phosphorylation by what enzyme

A

Hexokinase
Glucose 6P can’t be transported across plasma membrane
it enters various metabolic pathways

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7
Q

What inhibits hexokinase

A

feedback inhibition by its product glucose 6-P

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8
Q

in liver, glucose is phosphorylated by what enzyme

A

glucokinase

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9
Q

major distinction between hexokinase and glucokinase

A

glucokinase requires a much larger glucose concentration to achieve half saturation
higher Km

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10
Q

Does glucokinase or hexokinase prevent hyperglycemia following a carbohydrate-rich meal?

A

glucokinase functions to prevent hyperglycemia following a carbohydrate rich meal

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11
Q

Which 2 organs express glucokinase ?

A

liver and pancreas

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12
Q

Describe the kinetics of glucokinase

A

liver
high Km (low affinity for glucose)
high Vmax
not subject to feedback inhibition by glucose 6-P

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13
Q

Describe the kinetics of hexokinase

A

brain , muscles
low Km (high affinity for glucose)
low Vmax
subject to feedback inhibition by glucose 6-P

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14
Q

What is the effect of insulin on this glucokinase?

A

insulin induces synthesis of the glucokinase

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15
Q

Name 2 functions of glycolysis

A

degrading glucose to generate ATP

providing building blocks for synthetic reactions

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16
Q

how much ATP is consumed per mole of glucose that undergoes glycolysis

A

2 moles are consumed

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17
Q

how much ATP is generated per mole of glucose that undergoes glycolysis

A

4 moles generated

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18
Q

What is the net generation of ATP per mole of glucose - glycolysis

A

2 moles

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19
Q

What is the Major Regulatory enzyme in Glycolysis

A

Phosphofructokinase-1 (PFK1)

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20
Q

Name 3 enzymes of glycolysis that catalyze virtually Irreversible reactions

A

Hexokinase
PFK-1
pyruvate kinase (in liver)

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21
Q

What reaction does PFK-1 catalyze?

A

fructose 6-P –> fructose 1,6-bisphosphate

coupled to hydrolysis of ATP

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22
Q

Positive allosteric regulator of PFK1

A

AMP (+)

fructose-2,6-bisphosphate (+)

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23
Q

Allosteric inhibitor of PFK1

A

ATP (-)

citrate (-)

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24
Q

What reaction does PFK II catalyze?

A

fructose 6-P –> fructose 2,6-bisphosphate

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25
Q

PRK II is a sign of fed or fasting state?

A

fed

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26
Q

which 2 glycolytic intermediates liberate enough energy for driving ATP synthesis?

A

1,3-bisphosphoglycerate and phosphoenolpyruvate (PEP)

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27
Q

What are the 2 ATP-producing enzymes of glycolysis?

A

3-phosphoglycerate kinase and pyruvate kinase

28
Q

Pyruvate kinase catalyzes what reaction?

A

PEP –> pyruvate

29
Q

What covalent modification inhibits pyruvate kinase?

A

Phosphorylation

30
Q

What enzyme phosphorylate pyruvate kinase?

A

Protein Kinase A

31
Q

Name the allosteric inhibitors of Pyruvate Kinase

A

ATP
acetyl coenzyme (CoA)
alanine in liver only

32
Q

Name the allosteric activator of pyruvate kinase

A

fructose-1,6-bisphophate

33
Q

Which enzyme produces Nicotinamide Adenine Dinucleotide in Glycolysis?

A

glyceraldehyde-3-phosphate dehydrogenase

34
Q

How much NADH is produced per mole of glucose oxidized to pyruvate

A

2 moles

35
Q

Since erythrocytes do not contain mitochondria, what is the NADH produced in glycolysis used for?

A

to reduce pyruvate to lactate

36
Q

How is the reducing power of NADH transferred to the mitochondria?

A

via the glycerol-3-phopshate shuttle or malate aspartate shuttle

37
Q

What are the possible fates of pyruvate produced in the cell?

A 
it can be converted to 
lactate- LDH
alanine
 acetyl CoA- PDC 
 OAA- Pyruvate Carboxylase
38
Q

How many moles of ATP are required to generate glucose from pyruvate?

A

6 moles

39
Q

Under anaerobic conditions, pyruvate is converted to what molecule?

A

Lactate

40
Q

What enzyme catalyzes pyruvate to lactate?

A

Lactate dehydrogenase

41
Q

What reaction does the PDH complex catalyze?

A

Pyruvate + NAD+ + CoA –> Acetyl-CoA + CO2 + NADH

42
Q

What coenzymes are required by this enzyme?

A 
Thiamine pyrophosphate 
coenzyme A 
NAD+ 
flavin adenine dinucleotide 
lipoid acid
43
Q

PDH complex is similar to what other enzyme

A

alpha-ketoglutarate dehydrogenase complex

44
Q

PDH complex active in phosphorylated or nonphosphorylated state?

A

nonphosphorylated state

45
Q

what enzyme phosphorylates the PDH complex?

A

PDH kinase

46
Q

What molecules activate PDH kinase (thus inhibiting the PDH complex)?

A

Acetyl CoA

NADH

47
Q

What molecules inhibit PDH kinase (thus activating the pyruvate dehydrogenase complex)?

A

Pyruvate

decreased levels of ADP

48
Q

What enzyme dephosphorylates PDH complex?

A

PDH phosphorylase / phosphatase

49
Q

What molecule activates PDH phosphatase (thus activate PDH complex)?

A

Ca2+

50
Q

What are the major manifestations of PDH deficiency?

A

Lactic acidosis

neurological manifestations

51
Q

What is the treatment for PDH deficiency?

A

Increased intake of ketogenic nutrients

52
Q

SGLT1

A

small intestine, kidney

absorption of glucose

53
Q

GLUT2

A

liver and pancreatic beta cells
high Km (low affinity for glucose)
only transport glucose at high blood concentration
high Vmax

54
Q

GLUT4

A

skeletal muscle and adipose
insulin responsive
low Km (high affinity for glucose)

55
Q

glucose 6-P fates

A

glycogen
pyruvate
ribose 5-P
other pathways

56
Q

BPG shunt

A

1,3-bisphosphoglycerate - critical metabolic intermediate of glycolysis
shunt - glycolytic bypass unique to RBC , decrease in ATP production
regulate oxygen binding of hemoglobin
produces 2,3-BPG
regulated by 2,3BPG mutase/phosphatase

57
Q

2,3-BPG

A

lowers affinity of Hb for Oxygen

allowing O2 release in peripheral tissue

58
Q

glycolysis - delta G

A

negative delta G

-22 kcal

59
Q

Anerobic glycolysis produces no net change

A

NADH

NADH is reoxidized in cytosol by lactate dehydrgoensase

60
Q

conversion of glucose to 2 lactate generates

A

2 ATP from substrate level phosphorylation

61
Q

Lactic acidemia (acidosis)

A

blood lactate >5 mM
pH high NADH/NAD+ and low ATP
Tissue hypoxia

62
Q

Anerobic glycolysis vs Aerobric glycolysis

A

Anaerobic- 2 ATP , 2 Lactate

Aerobic- 2 ATP, 2 NADH , 2 pyruvate ~25ATP

63
Q

Brain & Muscle Pyruvate Kinase regulation?

A

contains no Allosteric Sites

no regulation

64
Q

Liver Pyruvate Kinase regulation?

A 
has allosteric sites
ATP  (-)
 Fructose 1-6-P (+)
 cAMP-PKA- phosphorylation (-) , fasting - glucagon high
alanine (-)
65
Q

Phosphofructokinase 1 regulation?

A

AMP, ADP (+)
fructose 2,6-bisP (+)- fed state- high insulin
ATP (-)
citrate (-)

66
Q

Substrate level phosphorylation

A

formation of high energy phosphate bond where none previously existed w/o utilization of oxygen

BCH MEtabolism (8 decks)

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