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SFM - Biochem - Quiz 1 > (L3) - Carbohydrate Metabolism > Flashcards

(L3) - Carbohydrate Metabolism Flashcards

1
Q

What cell types exclusively use glucose as their fuel source?

L3 S8

A
  • RBCs

- Brain (non-starvation)

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2
Q

What are the different types of glucose transporters, where are they found and what are their affinities?

L3 S10-11 LO1

A

GLUT1:

  • found in all cells; especially high in RBCs and brain
  • high affinity (Km: 1mM)

GLUT2:

  • found in liver and pancreas
  • low specificity (Km: 10mM)

GLUT3:

  • found in neurons
  • high affinity (Km: 1mM)

GLUT4:

  • found in skeletal muscle, adipose tissue, and heart
  • intermediate affinity (Km: 5mM)
  • INSULIN REGULATED vesicle fusion
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3
Q

What is the net yield of glycolysis per molecule of glucose?

L3 S13 LO1

A
  • 2 ATP
  • 2 NADH
  • 2 Pyruvate
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4
Q

What is the first phase of glycolysis and what occurs during it?

A

Investment
-use 2 ATP to trap glucose

Net reaction:
Glucose + 2 ATP -> fructose 1,6-BP

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5
Q

What does hexokinase do?

L3 S14 LO1

A

Converts glucose to glucose 6-P using ATP

Found in all cells

Inhibited by glucose-6P (feedback inhibition)

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6
Q

What does glucokinase do?

L3 S14 LO1

A

Converts glucose to glucose 6-P using ATP

Found only in the liver and pancreas

No feedback inhibition by glucose 6-P

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7
Q

What does phosphofructokinase do?

L3 S14

A

RATE LIMITING

Converts fructose 6-P to fructose. 1,6-BP

Inhibited by ATP and citrate

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8
Q

What is the second phase of glycolysis and what occurs during it?

L3 S15 LO1

A

Splitting
-goes from 1 6C molecule to 2 3C molecules

Net reaction:
-Fructose 1,6-BP -> 2 Glyceraldehyde 3-P

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9
Q

What does aldolase do?

L3 S15 LO1

A

Splits fructose 1,6-BP into DHAP and G3P

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10
Q

What does triose phosphate isomerase do?

L3 S15

A

Interconverts DHAP and G3P

G3P is used in next step of glycolysis

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11
Q

What is the third phase of glycolysis and what occurs during it?

L3 S16 LO1

A

Recoup/payoff

  • 4ATP and 2NADH are generated
  • pyruvate is generated

Net reaction:
-2 G3P + 4 ADP + 2 NAD+ -> 2 Pyruvate + 4 ATP + 2 NADH

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12
Q

What does glyceraldehyde 3-P dehydrogenase do?

L3 S16 LO1

A

Converts G3P to 1,3-BPG

Generates NADH

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13
Q

What does phosphoglycerate kinase do?

L3 S16 LO1

A

Converts 1,3-BPG to 3-phosphoglycerate

Generates ATP

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14
Q

What does pyruvate kinase do?

L3 S16 LO1

A

Converts phosphoenolpyruvate to pyruvate

Generate ATP

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15
Q

What are the regulated steps of glycolysis?

L3 S19 LO1

A
  • hexokinase/glucokinase
  • phosphofructokinase-1
  • pyruvate kinase
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16
Q

How is hexokinase/glucokinase regulated?

L3 S20-21 LO1

A

Hexokinase is inhibited by G6P

Glucokinase is minimally affected by G6P

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17
Q

How is PFK-1 regulated?

L3 S22-23 LO1

A

Insulin actives phosphatases which activates PFK-2’s kinase activity and activates PFK-1

Glucagon activates PKA which activates PFK-2’s phosphorylase activity and inactivates PFK-1

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18
Q

What is Tarui disease?

L3 S24 LO1

A

GSD VII

Deficiency in PFK-1 (rate limiting enzyme of glycolysis)

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19
Q

How is pyruvate kinase regulated?

L3 S25 LO1

A

Activated by F1,6BP and insulin (activation of phosphatases)

Inhibited by ATP and glucagon (activation of PKA)

20
Q

What are the possible fates of G6P?

L3 S27-28

A
  • Glycolysis (pyruvate)
  • Glycogen synthesis (glycogen)
  • Pentosephosphate pathway (ribose)
21
Q

How do defects in glycolysis affect RBCs?

L3 S31-32 LO1

A

Glycolysis is only means of ATP production for RBCs

Failure of glycolysis leads to hemolytic anemia.

22
Q

What is Fanconi-Bickel syndrome?

L3 S37 LO1

A

Mutation in GLUT2 transporter (liver and pancreatic β cells

Results in inability to take up glucose efficiently in those cells

23
Q

What steps of glycolysis must be bypassed in gluconeogenesis?

L3 S42 LO2

A

Hexokinase/glucokinase
-bypassed by glucose 6-phosphatase

Phosphofructokinase
-bypassed by fructose 1,6-bisphosphatase

Pyruvate kinase
-bypassed by PEP carboxylase and pyruvate carboxylase

24
Q

What factors regulate glycolysis and gluconeogenesis?

L3 S44 LO2

A

High energy signals (ATP, glucagon) inhibit glycolysis and stimulate gluconeogenensis

Low energy signals (ADP/AMP, insulin) stimulate glycolysis and inhibit gluconeogenesis

25
What does pyruvate carboxylase do? L3 S45 LO2
Converts pyruvate to oxaloacetate
26
What does malate dehydrogenase do? L3 S46 LO46
Converts mitochondrial oxaloacetate into malate which can leave the mitochondria Malate is converted back into oxaloacetate in the cytoplasm
27
What does phsophoenolpyruvate kinase do? L3 S47 LO2
Converts oxaloacetate to PEP using GTP
28
What does fructose 1,6-bisphosphatase do? L3 S47 LO2
RATE LIMITING Converts fructose 1,6-bisphosphatase to fructose 6-P
29
What does glucose 6-phosphatase do? L3 S47 LO2
Dephosphorylates G6P to glucose ONLY found in liver, kidneys, SI, and pancreas
30
What is GLUT7? L3 S48 LO2
Removes glucose from the ER after being produced by glucose 6-phosphatase
31
What is the Cori cycle? L2 S49 LO2
Links lactate production in muscles and RBCs to glucose production in liver
32
What is Von Gierke disease? L3 S54 L2
GSD1a Deficiency in glucose 6-phosphatase Results in inefficient release of glucose from the liver and build of of stored glycogen in liver
33
What is the significance of fructose metabolism on glycolysis? L3 S63 LO3
Fructose enters glycolysis as G3P, after rate limiting step. High consumption of fructose is linked to obesity because of this.
34
What is the significance of galactosemia? L3 S65 LO3
Due to deficiency in galactose 1-P uridyltransferase (GALT) that results in accumulation of galactose. Excess galactose is converted to galactitol which can accumulate in the eyes leading to cataracts
35
What is the rate limiting step of the PPP? L3 S69-70 LO4
Glucose 6-phosphate dehydrognase
36
What is the first step of the PPP? L3 S68 LO4
Oxidative phase Contains rate limiting step Produces NADPH and ribulose 6-phosphate
37
What is the second step of the PPP? L3 S68 LO4
Non-oxidative Products shunt to glycolysis/gluconeogenesis or nucleotide synthesis
38
What are the main products of PPP and what are they used for? L3 S73 LO4
Ribose 5-P: -used in nucleotide synthesis NADPH: -Used as a reducing agent in anabolic reactions
39
What are the non-reducing and reducing ends of glycogen? L3 S75 LO5
Reducing: - 1’ end - connected to glycogenin - does not grow Non-reducing: - 4’ end - site for growth and shortening
40
What is phosphoglucomutase? L3 S79 LO5
Converts glucose 6-P into glucose 1-P
41
What does UDP-glucose pyrophosphorylase do? L3 S79 LO5
Converted glucose 1-P into UDP-glucose, the building block of glycogen
42
What does glycogen synthase do? L3 S80 LO5
RATE LIMITING glycogen synthesis Forms α-1,4 glycosidic bonds elongating glycogen
43
What does glucosyl 4:6 transferase do? L3 S80 LO5
Takes roughly 7 glucose chain from glycogen and adds it onto the side of the chain via a 1,6 glycosidic bond
44
What does glycogen phosphorylase do? L3 S82 LO5
RATE LIMITING glycogenolysis Breaks glycogen from non-reducing end into glucose 1-P
45
What does debranching enzyme do? L3 S83 LO5
Removes distal 3 of 4 remaining glucose of a branch and adds to end of chain
46
What does α-1,6-glucosidase do? L3 S83 LO5
Cleaves last glucose of branch generating a glucose
47
How do fed and fasting states regulate glycogenesis and glycogenolysis? L3 S87 LO5
Fed state: - high insulin and glucose - trigger dephosphorylation of glycogen synthase (activating) and glycogen phosphorylase (inactivating) Starving state: - high glucagon, low glucose - triggers phosphorylation of glycogen synthase (inactivating) and glycogen phosphorylase (activating)

SFM - Biochem - Quiz 1 (16 decks)

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