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MBOD Week 8 > Glycolysis > Flashcards

Glycolysis Flashcards

1
Q

T or F: Glycolysis only occurs in Liver and Skeletal muscle cells

A

False

Glycolysis occurs in all cell types

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2
Q

What is the name of the process that transfers an inorganic phosphate from a high-energy intermediates to ADP?

A

Substrate-level Phosphorylation

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3
Q

In what cellular location does glycolysis take place?

A

Glycolytic enzymes are found in the Cytosol

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4
Q

What is the main function of glycolysis? Other functions?

A

Main Function: Produce ATP in cells

Other Functions: Produce metabolic intermediates used for other metabolic pathways

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5
Q

T or F: All cells exhibit the same glycolytic activity

A

False
The activity of glycolysis (Amount of Glucose oxidized per minute) Varies in different tissues
Example: RBC have low activity, while Skeletal Muscles have high activity

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6
Q

The phosphorylation of glucose to glucose 6-phosphate is catalyzed by what enzyme(s)?

A

Hexokinase or Glucokinase (In liver)

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7
Q

T or F: The conversion of glucose to glucose 6-phosphate is a irreversible reaction

A

True

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8
Q

Which enzyme has the lowest Km (Highest affinity) for glucose?

A

Hexokinase has a lower Km or Higher affinity for glucose

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9
Q

T or F: Hexokinase is non-specific, meaning it can phosphorylate other sugars such as fructose

A

True

Hexokinase can phosphorylate other sugars. However, it has a greater affinity (lower Km) for glucose

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10
Q

The enzyme phosphoglucose Isomerase catalyzes the conversion of glucose 6-phosphate to what product?

A

Phosphoglucose Isomerase catalyzes the conversion of glucose 6-phosphate to Fructose 6-phosphate

Isomerized from Aldehyde to Keto sugar

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11
Q

What is the first committed step of glycolysis?

A

The phosphorylation of Fructose 6-phosphate by Phosphofructokinase-1 (PFK-1) to Fructose 1,6-bisphosphate
- Rxn is irreversible

PFK-1 is rate limiting enzyme

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12
Q

Which two reactions of Glycolysis CONSUME ATP?

A
  1. Glucose + ATP –> Glucose 6-phosphate +ADP
    (Hexokinase or glucokinase)
  2. Fructose 6-P + ATP –> Fructose 1,6-BP
    (PFK-1)
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13
Q

The cleavage of Fructose 1,6-BP by Aldoase produces what two triose phosphates?

A
  1. Glyceraldehyde 3-phosphate (G3P)
  2. Dihydroxyacetone Phosphate *

*Dihydroxyacetone Phosphate gets isomerized to G3P by triose phosphate isomerase

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14
Q

The oxidation and phosphorylation of Glyceraldehyde 3-phosphate (G3P) is catalyzed by what enzyme? and what are the products of this reaction?

A

Catalyzed by Glyceraldehyde 3-P dehydrogenase

Products: 1,3-bisphosphoglycerate, NADH , and H+

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15
Q

How many moles of:
1. NADH
2. ATP
are produced per 1 mole of glucose in the ATP-generation phase of Glycolysis?

A

For 1 mole of glucose oxidized:
2 NADH and 4 ATP* are produced

*ATP-generation phase produces 4 ATP but net production is 2 mol ATP because 2 moles of ATP were consumed in the ATP-utilization phase

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16
Q

What two reactions of glycolysis produce ATP?

A
  1. 1,3-Bisphosphoglycerate —> 3-phosphoglycerate
    (via Phosphoglycerate Kinase)
  2. Phosphoenol pyruvate —> Pyruvate
    (via Pyruvate Kinase)
17
Q

What determines the fate of pyruvate and NADH after glycolysis?

A

The availability of oxygen

18
Q

How is NAD+ replenished during anaerobic conditions of glycolysis? Where does this occur?

A

Lactate Dehydrogenase (LDH) converts pyruvate to lactate, which oxidizes NADH back to NAD+

This occurs in the cytosol

NAD+ is needed as an electron acceptor for the conversion of G3P to 1,3-Biisphosphoglycerate

19
Q

What is the fate of pyruvate in the presence of oxygen?

A

It is completely oxidized to CO2

this process produces about 12.5 mol ATP/ pyruvate

20
Q

Under aerobic conditions, where does the oxidation of NADH back to NAD+ occur?

A

In the Mitochondria

21
Q

T or F: NADH diffuses through the inner mitochondrial membrane to reach the electron transport chain

A

False

The inner mitochondrial membrane is impermeable to Cytosolic NADH

The transfer of electrons require the use of Shuttle Systems

22
Q

What are the names of the two shuttle systems used to transfer reducing equivalents across the inner mitochondrial membrane?

A
  1. Glycerol 3-phosphate shuttle

2. Malate-Aspartate Shuttle

23
Q

In the Glycerol 3-phosphate shuttle system, what enzyme transfers electrons from cytosolic NADH to Dihydroxyacetone-phosphate (DHAP)?

A

Glycerol 3-phosphate dehydrogenase

This transfer produces Glycerol 3-phosphate, which then diffuses through the outer mitochondrial membrane

24
Q

After diffusing through the outer mitochondrial membrane, Glycerol 3-phosphate transfers electrons to what e- acceptor?

A

Glycerol 3-phosphate transfers electrons to (inner) membrane-bound Flavin Adenine Dinucleotide (FAD)

This produces a FAD(2H) which eventually donates electrons to Coenzyme Q (CoQ) resulting in the generation of ATP via oxidative phosphorylation

25
Q

In the Malate- Apartate Shuttle System, what enzyme transfers electrons from NADH to cytosolic oxaloacetate?

A

Malate Dehydrogenase

NADH + oxaloacetate —–> Malate

26
Q

How does Malate cross the inner mitochondrial membrane?

A

Malate is exchanged for alpha-ketoglutarate by a specific translocase

Once in the mitochondrial matrix, malate is oxidized back to oxaloactetate by mitochondrial Malate dehydrogenase to generate NADH

NADH donates electrons to ETC

27
Q

Which shuttle system results in the production of more ATP?

A

The Malate-Aspartate shuttle (about 2.5 mole ATP)

glycerol 3-phosphate shuttle ~ 1.5 mole ATP

28
Q

Oxaloacetate cannot pass back through the inner mitochondrial membrane. How does it get back to cytosol?

A

Via Aspartate

In the matrix, Transamination reactions transfer an amino group to ocaloacetate to form aspartate

Aspartate is transported out to cytosol via an aspartate-glutamate exchange translocase

29
Q

What are the four major enzymes regulated in glycolysis?

A
  1. Hexokinase (or glucokinase)
  2. Phosphofructokinase-1 (PFK-1)
  3. Pyruvate Kinase
  4. Pyruvate Dehydrogenase*

*coverts pyruvate to Acetyl CoA (kinda after glycolysis)

30
Q

What regulates the activity of Hexokinase?

A

Glucose 6-phosphate inhibits hexokinase
(negative feedback)

G6-P does NOT inhibit glucokinase

31
Q

What regulates Glucokinase?

A

Insulin induces GK

32
Q

What are the activators and inhibitors of Phosphofructokinase-1?

A

PFK-1 Activators: AMP and Fructose 2,6-bisphosphate

PFK-1 Inhibitors: ATP and Citrate

33
Q

PFK-1 is an allosteric enzyme with how many binding sites?

A

6

2 for substrates ( Fructose 6-phosphate, and ATP)
4 for Allosteric regulators

34
Q

How does AMP and F 2,6-BP work to activate PFK-1?

A

AMP binds to activator site and increase affinity of PFK-1 for Fructose 6-phosphate

F 2,6-BP binds to PFK-1 and removes the inhibitory affect of ATP

35
Q

Fructose 2,6-Bisphosphate is not an intermediate of glycolysis. How is it made?

A

The bifunctional enzyme, Phosphofructokinase-2, converts Fructose 6-phosphate to Fructose 2,6-Bisphosphate

36
Q

How is Pyruvate Kinase regulated in the Liver?

A

Activated by: Fructose 1,6-Bisphosphate

Inhibited by: ATP and Alanine

37
Q

How is Pyruvate Kinase regulated in skeletal muscle?

A

Trick Question!

  • Pyruvate kinase in not involved in regulation of glycolysis in skeletal muscle
  • the isoenzyme in skeletal muscle does not have allosteric site
  • same for isoenzymes in brain and heart

MBOD Week 8 (6 decks)

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