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MSK Midterm > Biochem > Flashcards

Biochem Flashcards

0
Q

What are the major products of glycolysis (for each glucose) under anaerobic conditions?

A

2 lactate
2 ATP
(no NADH)

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1
Q

What are the major products of glycolysis (for each glucose) under aerobic conditions?

A

2 pyruvate
2 NADH
2 ATP

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2
Q

What is the purpose of the first step of glycolysis?

A

The first step is the phosphorylation of glucose at the 6-carbon position. This traps the glucose within the cell, and is thermodynamically irreversible.

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3
Q

For which major pathways is glucose-6-phosphate a starting material? (3)

A
  1. Glycolysis: to generate ATP, when there is a demand
  2. Glycogen synthesis: to store glucose when at rest (for later demand)
  3. Pentose phosphate pathway: regenerate NADPH from NADP+ after the store has been depleted (when at rest)
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4
Q

Hexokinase vs Glucokinase? Explain the purpose of the different Kms.

A

Both convert glucose to G6P.
Hexokinase: found in peripheral tissue (e.g., muscle), low Km (micromolar - greater affinity for glucose), inhibited by G6P.
Glucokinase: found in liver, high Km (5 mM - lower affinity). Not inhibited by product.
The liver is one of the major sources of glucose (stored as glycogen) for when blood glucose is low. Using an enzyme with lower affinity means that the liver won’t use the glucose that needs to exit to the rest of the body, and that tissues that really need it for fuel (muscle, brain) will get first crack.

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5
Q

Which are the irreversible steps of glycolysis?

A

Step 1 (hexokinase/glucokinase), Step 3 (PFK-1), Step 10 (pyruvate kinase)

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6
Q

Which transporters do we NOT have for the inner mitochondrial membrane? (3)

A
  1. oxaloacetate
  2. NAD(H)
  3. acetyl-CoA
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7
Q

What important molecules have transporters for the inner mitochondrial membrane? (5)

A
  1. malate
  2. aspartate
  3. glutamate
  4. pyruvate
  5. alpha-ketoglutarate
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8
Q

How do the electrons needed to regenerate NADH from NAD+ get across the inner mitochondrial membrane? (2)

A
  1. glycerol phosphate shuttle (most tissues)

2. malate aspartate shuttle (mainly liver, kidney, heart)

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9
Q

What enzyme produces lactate from pyruvate under anaerobic conditions?

A

Lactate dehydrogenase

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10
Q

Compare overall efficiency of aerobic vs anaerobic glycolysis.

A

Anaerobic glycolysis produces 2 ATP per glucose, compared to 30-32 ATP for aerobic glycolysis (and TCA, ETC), but anaerobic is 30 times faster than aerobic. In the end, anaerobic glycolysis (using the breakdown of glycogen as a fuel) produces more ATP per second than aerobic. BUT production of lactate can lead to lactic acidosis.

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11
Q

Which tissues are dependent on anaerobic glycolysis? (5)

A
  1. RBCs (no mitochondria)
  2. White blood cells
  3. Lens of the eye
  4. Kidney medulla
  5. Exercising muscle
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12
Q

How can the body use lactate once its produced?

A
  1. Fuel (resting muscle, heart)
  2. Catabolism (lactate –> pyruvate –> TCA)
  3. Gluconeogenesis (liver can convert lactate –> glucose)
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13
Q

What are the major products of glycolysis (for each glucose) under aerobic conditions?

A

2 pyruvate
2 NADH
2 ATP

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14
Q

What are the major products of glycolysis (for each glucose) under anaerobic conditions?

A

2 lactate
2 ATP
(no NADH)

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15
Q

What is the purpose of the first step of glycolysis?

A

The first step is the phosphorylation of glucose at the 6-carbon position. This traps the glucose within the cell, and is thermodynamically irreversible.

16
Q

For which major pathways is glucose-6-phosphate a starting material? (3)

A
  1. Glycolysis: to generate ATP, when there is a demand
  2. Glycogen synthesis: to store glucose when at rest (for later demand)
  3. Pentose phosphate pathway: regenerate NADPH from NADP+ after the store has been depleted (when at rest)
17
Q

Hexokinase vs Glucokinase? Explain the purpose of the different Kms.

A

Both convert glucose to G6P.
Hexokinase: found in peripheral tissue (e.g., muscle), low Km (micromolar - greater affinity for glucose), inhibited by G6P.
Glucokinase: found in liver, high Km (5 mM - lower affinity). Not inhibited by product.
The liver is one of the major sources of glucose (stored as glycogen) for when blood glucose is low. Using an enzyme with lower affinity means that the liver won’t use the glucose that needs to exit to the rest of the body, and that tissues that really need it for fuel (muscle, brain) will get first crack.

18
Q

Which are the irreversible steps of glycolysis?

A

Step 1 (hexokinase/glucokinase), Step 3 (PFK-1), Step 10 (pyruvate kinase)

19
Q

Which transporters do we NOT have for the inner mitochondrial membrane? (3)

A
  1. oxaloacetate
  2. NAD(H)
  3. acetyl-CoA
20
Q

What important molecules have transporters for the inner mitochondrial membrane? (5)

A
  1. malate
  2. aspartate
  3. glutamate
  4. pyruvate
  5. alpha-ketoglutarate
21
Q

How do the electrons needed to regenerate NADH from NAD+ get across the inner mitochondrial membrane? (2)

A
  1. glycerol phosphate shuttle (most tissues)

2. malate aspartate shuttle (mainly liver, kidney, heart)

22
Q

What enzyme produces lactate from pyruvate under anaerobic conditions?

A

Lactate dehydrogenase

23
Q

Compare overall efficiency of aerobic vs anaerobic glycolysis.

A

Anaerobic glycolysis produces 2 ATP per glucose, compared to 30-32 ATP for aerobic glycolysis (and TCA, ETC), but anaerobic is 30 times faster than aerobic. In the end, anaerobic glycolysis (using the breakdown of glycogen as a fuel) produces more ATP per second than aerobic. BUT production of lactate can lead to lactic acidosis.

24
Q

Which tissues are dependent on anaerobic glycolysis? (5)

A
  1. RBCs (no mitochondria)
  2. White blood cells
  3. Lens of the eye
  4. Kidney medulla
  5. Exercising muscle
25
Q

How can the body use lactate once its produced?

A
  1. Fuel (resting muscle, heart)
  2. Catabolism (lactate –> pyruvate –> TCA)
  3. Gluconeogenesis (liver can convert lactate –> glucose)
26
Q

List the path of electrons in the ETC originating on NADH.

A
  1. Complex I (Flavin mononucleotide and 9 iron sulfur clusters)
  2. CoQ
  3. Complex III (2 b-type cytochromes, 2 iron sulfur clusters, cyctochrom c1; Q cycle)
  4. Cytochrome C
  5. Complex IV (cytochrome a, cytochrome a3, CuB, CuA)
27
Q

Where does cyanide bind to disrupt metabolic processes?

A

Complex IV in the electron transport chain.

28
Q

How many protons are needed to pump through ATP synthase to synthesize one ATP?

A

2-3 protons per ATP

29
Q

How many protons are pumped per electron pair for each complex of the ETC?

A 
Complex I: 4 H+
Complex II: 0 H+
CoQ: 0 H+
Complex III: 4 H+
Cytochrome C: 0 H+
Complex IV: 2 H+
30
Q

How many protons are pumped per pair of electrons borne by NADH vs FADH2? What’s the equivalent in ATP synthesized?

A

NADH: 10 H+, 2.5 ATP
FADH2: 6 H+, 1.5 ATP

31
Q

List the path of electrons in the ETC originating on FADH2.

A
  1. Complex II (3 iron sulfur clusters, cytochrome b560)
  2. CoQ
  3. Complex III (2 b-type cytochromes, 2 iron sulfur clusters, cyctochrom c1; Q cycle)
  4. Cytochrome C
  5. Complex IV (cytochrome a, cytochrome a3, CuB, CuA)
33
Q

What is the committing, rate-limiting step of glycolysis?

A

Step 3: conversion of F6P to F16BP via phosphofructokinase-1.

34
Q

What is considered to be the baseline blood glucose level?

A

5 mM

35
Q

What allosterically activates PFK-1? (2)

A
  1. F26BP (liver, made in response to higher insulin relative to glucagon)
  2. AMP (muscle)
36
Q

What allosterically inhibits PFK-1? (3)

A
  1. ATP (all tissues)
  2. Citrate (all tissues)
  3. H+ (all tissues)

MSK Midterm (9 decks)

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