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Year 1: 01. Scientific Foundations Quiz 1 > Lecture 3: Carbohydrate Metabolism > Flashcards

Lecture 3: Carbohydrate Metabolism Flashcards

1
Q

What does GLUT 1 transport? Does it have a low or high affinity?

A 
RBC and Brain
High Affinity (so low Km)
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2
Q

What does GLUT 2 transport? Does it have a low or high affinity?

A 
Liver
Low Affinity (so high Km)
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3
Q

What does GLUT 3 transport? Does it have a low or high affinity?

A 
Neurons
High Affinity (so low Km)
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4
Q

What does GLUT 4 transport? What is it dependent on?

A

Skeletal Muscle, Heart, Adipose Tissue

Insulin dependent

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5
Q

When insulin signals a cell that utilizes GLUT 4, what happens?

A

GLUT 4 transporter sequestered in cell will insert itself into plasma membrane to induce glucose uptake

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6
Q

Where does glycolysis occur?

A

Cytoplasm

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7
Q

What is the net yield of glycolysis with one glucose molecule?

A

2 ATP
2 NADH
2 pyruvate

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8
Q

What is the difference between hexokinase and glucokinase?

What do these enzymes do?

A

Hexokinase: utilized in all cells
-High affinity (low Km)

Glucokinase: pancreas and liver only

  • Low affinity (high Km)
  • Most active with high glucose levels

Both convert glucose to glucose 6-P

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9
Q

What activates and inhibits step 1 of glycolysis?

A

Activators:
Glucose
Insulin
Fructose 1-P

Inhibitors
Glucose 6-P/Fructose 6-P
Glucagon

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10
Q

What is the rate limiting step of glycolysis? What enzyme is involved?

A

Step 3: Fructose 6-P –> Fructose 1,6-BP

via PFK-1 (phosphofructokinase-1)

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11
Q

What activates and inhibits rate limiting step of glycolysis?

A

Activators:
Fructose 2,6-P
AMP

Inhibitors:
Citrate
ATP

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12
Q

Which step yields NADH?

A

Step 6: G3P –> 1,3 BPG

via Glyceraldehyde 3P dehydrogenase (GADPH)

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13
Q

When 1,3BPG –> 3-PG, what enzyme is used and what is a product of this reaction?

A

Phosphoglycerate kinase

ATP

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14
Q

How is pyruvate formed?

A

PEP –> Pyruvate via pyruvate kinase

ATP is produced

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15
Q

How does glucokinase allow glucose to enter liver and pancreatic cells?

A

When there is high glucose, Fructose 6-P will promote the translocation of nucleus.

Most of the time, glucokinase is sequestered by GK-Regulatory Protein. Glucokinase moves to cytoplams.

Insulin induces synthesis.

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16
Q

How does PFK-2 regulate glycolysis?

A

Fructose 6-P produces Fructose 2,6-BP via PFK 2.
PFK 2 promotes PFK 1 (hence promoting glycolysis)

When PFK is dephosphorylated, it is favored by insulin.
When PFK is phosphorylated, it is favored by glucagon.

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17
Q

What happens to glycolysis when insulin levels are high and glucagon levels are low? (fed state)

A

Insulin promotes dephosphorylation of PFK 2.

Fru 2,6 BP is produced –> promote PFK 1

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18
Q

What happens to glycolysis when glucagon levels are high and insulin levels are low? (fasting state)

A

Glucagon induces Protein Kinase A, which phosphorylates PFK-2, reducing PFK-1 activity.

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19
Q

What is Tarui Disease?

A

Deficiency of PFK-1

-Can cause muscle weakness

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20
Q

How is pyruvate kinase regulated?

A

Activators:
Insulin: dephosphorylates PK
Fructose 1,6-BP

Inhibitors:
Glucagon: phosphorylates PK
Alanine
ATP

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21
Q

What pathways can intermediate Glucose 6-P be utilized in?

A

Glucose 6-P:
-Pentose Phosphate Pathway (precursor)

As Glucose 1-P:

  • Galactose metabolism
  • Glycogen Synthesis
  • Uronic Acid Pathway
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22
Q

What are the fates of pyruvate?

A

Acetyl Co A –> TCA Cycle
Alanine –> Protein synthesis, gluconeogenesis, urea cycle
Oxaloacetate –> Gluconeogensis
Lactate –> Cori Cycle

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23
Q

What cells are most affected by glycolysis disorders? What is the biggest clinical finding?

A

Red Blood Cells (no mitochondria)

-hemolytic anemia

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24
Q

When the brain can no longer utilize glucose as a fuel source, what will it use?

A

Ketone Bodies

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25
What are clinical markers for hemolytic anemia?
Elevated Lactate Dehydrogenase | Unconjugated bilirubin
26
What is mutated in Fanconi-Bickel Syndrome?
GLUT 2 | -liver and pancreas can't take up glucose
27
Where does gluconeogenesis take place? Why does it take place?
Liver, kidney, and small intestine | -Glucose and glycogen stores are depleted
28
What are major precursors of gluconeogenesis?
Pyruvate Derivatives - lactate - amino acids - glycerol
29
What are enzymes found in gluconeogenesis and not glycolysis?
Pyruvate Carboxylase PEP carboxykinase Fructose 1,6-bisphosphatase [Rate Limiting] Glucose 6-phosphatase
30
How much ATP/GTP is used in gluconeogenesis?
6 ATP - 2 from pyruvate--> oxaloacetate - 2 from oxaloacetate --> PEP - 2 from 3-PGA --> 1,3 BP
31
Pyruvate Carboxylase is found where? What is an important cofactor?
PC is found in mitochondria | Imp cofactor - Biotin
32
What regulates Pyruvate Carboxylase?
Activators - Acetyl Co-A - cortisol Inhibitors -ADP
33
How does pyruvate leave the mitochondria?
After being carboxylated to oxaloacetate, it is reduced to malate and leaves via the shuttle -Enzyme: mitochondrial malate dehydrogenase In the cytosol, it is oxidized back to OAA. -Enzyme: cytosolic malate dehydrogenase
34
What regulates PEPCK? | OAA --> PEP
Activators: - Cortisol - Glucagon - Thyroxine
35
What regulates Fructose 1,6 Bisphosphatase? | [Rate limiting]
Activators: - Cortisol - Citrate Inhibitors - AMP - Fructose 2,6 BP
36
What regulates Glucose 6-phosphatase?
Activators: | -Cortisol
37
Where is Glucose 6-phosphatase?
lumen of ER - Glucose 6-P is transported into ER - Glucose leaves ER via GLUT 7
38
What are gluconeogenesis precursors?
Uses Glucose 6-P - Galactose - Glycogen G3P -Fructose DHAP -glycerol TCA Cycle - Propionate - amino acids (except leucine, lysine) Pyruvate - lactate - alanine
39
What is F1,6 BP Deficiency?
Lacking F1,6 Bisphosphatase | -similar to Tauri
40
What is Von Gierke Disease?
Deficiency in Glucose-6 phosphatase
41
GLUT 5 transports what? Where does it do this?
Transports Fructose | -basal and apical side
42
What does SGLT-1 transport?
Glucose, Galactose, Sodium | intestine to enterocyte
43
What does GLUT 2 transport?
Glucose, Galactose, Fructose | to bloodstream
44
What is the Cori Cycle?
Liver takes up lactate from muscles and converts it back to glucose for muscles to use.
45
What is the Polyol Pathway?
Glucose --> Sorbitol --> Fructose
46
What happens if there is an accumulation of Sorbitol?
Water influx that causes swelling - Retinopathy - Cataracts - Peripheral Neuropathy
47
What makes fructose metabolism special (compared to glycolysis?)
Can skip rate limiting step of glycolysis Fru --> Fru-P -----> G3P
48
What is the rate limiting step in galactose metabolism?
Galactose 1-P --> Glucose 1-P | via GALT
49
What is Galactosemia?
Deficiency in GALT enzyme or Galactokinase Symptoms for Classic Galactosemia - Vomiting/Diarrhea after consuming milk - Enlargement of liver - Cataracts Symptoms in Deficiency in Galactokinase -build of galactitol (cataracts)
50
What is the point of pentose phosphate pathway?
Produce NADPH and sugar for DNA/RNA?
51
What happens in the oxidative phase of PPP?
Glucose 6-P will eventually become Ribose 5-P (3 steps) | -Rate limiting: G6P Dehydrogenase
52
What happens in the non-oxidative phase of PPP?
Reversible reactions with end products that can enter glycolytic and gluconeogenic reactions.
53
What regulates Pentose Phosphate Pathway?
Activators: - Rapidly dividing cells (need ribose) - NADPH needed for FA synthesis
54
What is rate limiting step in Glycogensis?
Glucose Synthase | UDP-Glucose --> Glycogen
55
What linkage is used to extend chain?
alpha 1,4
56
What linkage is used for branches of chains?
alpha 1,6 via glucosyl (4:6) transferase
57
What is the difference between how liver and muscle cels utilize Glucsoe 1-P
Liver: Glu 1-P --> Glu 6-P --> Glucose Muscle: Glu 1-P --> Glu 6-P --> Glycolysis and TCA cycle
58
What is GSD 0?
Deficiency in glycogen synthase
59
What is GSD 1a?
Von Gierke | Deficiency in Glucose 6-phosphatase
60
What is GSD II?
Pompe Disease | Deficiency in Acid Maltase
61
What is GSD III?
Cori Disease | Deficiency in alpha 1,6 branching enzyme
62
What is GSD IV?
Andersen Disease | Deficiency in Glucosyl (4:6)
63
What is GSD V?
McArdle Disease | Deficiency in muscle glycogen phosphorylase
64
What is GSD VI?
Hers Disease | Deficiency in liver glycogen phosphorylase

Year 1: 01. Scientific Foundations Quiz 1 (11 decks)

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