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BC2002: Principles Of Metabolic Pathways > Carbohydrate Catabolism > Flashcards

Carbohydrate Catabolism Flashcards

1
Q

Glucose, Fatty Acids and most amino acids all converge in catabolism to form which ONE of the following biomolecules?

A) Pyruvate
B) Glycogen
C) Acetyl-CoA
D) Hexokinase
E) Starch

A

C) Acetyl-CoA
(2C)

  • Stage 1 of catabolism
  • End product of Glycolysis
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2
Q

Which ONE of the following amounts in the nearest approximation the complete oxidation of glucose in the presence of oxygen?

A) 3000 kJ/mol
B) 30 kJ/mol
C) 3 kJ/mol
D) 3000 kJ/mol
E) 10,000 kJ/mol

A

A) 3000 kJ/mol

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3
Q

Which ONE of the following pathways is responsible for the major flux of carbon in cells?

A) Citric Acid Cycle
B) Gluconeogenesis
C) Beta-Oxidation
D) Glycolysis
E) None of the above

A

D) Glycolysis

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4
Q

Which ONE of the following describes the number of enzymes that function in glycolysis and the localisation of these enzymes in cells?

A) 8, Cytosol
B) 5, Cytosol
C) 5, Mitochondria
D) 10, Nucleus
E) 10, Cytosol

A

E) 10, Cytosol

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5
Q

What is the name of this biomolecule?

A) Acetyl-CoA
B) Glucose
C) Fructose-6-Phosphate
D) Pyruvate
E) Glyceraldehyde 3-Phosphate

A

D) Pyruvate

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6
Q

Which ONE of the following describes the total amount of energy obtained during glycolysis?

A) 2 NADH and 2 ATP
B) 4 NADH and 2 ATP
C) 2 NADH and 4 ATP
D) 2 NADH and 1 ATP
E) 1 ATP and 2 NADH

A

A) 2 ATP and 2 NADH

Exergonic pathway

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7
Q

Which ONE of the following enzymes converts phosphoenolpyruvate to pyruvate in glycolysis?

A) Pyruvate kinase
B) Pyruvate carboxylase
C) Phosphoenolpyruvate kinase
D) Pyruvate dehydrogenase
E) None of the above

A

A) Pyruvate kinase

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8
Q

Which ONE of the following enzymes is the committed step in glycolysis?

A) Hexokinase
B) Phosphofructokinase-1
C) Pyruvate kinase
D) Glyceraldehyde 3-Phosphate Dehydrogenase
E) Glucose 6-Phosphate

A

B) Phosphofructokinase-1

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9
Q

Which ONE of the following enzymes do vertebrates lack, preventing them from converting pyruvate to ethanol?

A) Pyruvate Decarboxylase
B) Pyruvate Kinase
C) Pyruvate Dehydrogenase
D) Pyruvate Isomerase
E) Pyruvate Mutase

A

A) Pyruvate Decarboxylase

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10
Q

Which of the following group of 2 enzymes convert pyruvate to ethanol?

A) Pyruvate Carboxylase and Alcohol Dehydrogenase
B) Pyruvate Decarboxylase and Alcohol Dehydrogenase
C) Pyruvate Kinase and Lactate Dehydrogenase
D) Lactate Dehydrogenase and Pyruvate Carboxylase
E) Hexokinase and Phosphofructokinase-1

A

B) Pyruvate Decarboxylase and Alcohol Dehydrogenase

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11
Q

What are the THREE stages of catabolism in the presence of O2?

A
  1. Acetyl-CoA production
  2. Acetyl-CoA oxidation
  3. Electron transfer and oxidative phosphorylation
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12
Q

What are the major nutrients used for energy?

A
  • Carbohydrates
  • Proteins
  • Fats
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13
Q

In what tissue/cell types is glucose the major source of energy?

A
  • Brain
  • Erythrocytes
  • Renal medulla
  • Sperm
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14
Q

What are some of the things E.coli synthesise from glucose?

A

Carbon skeletons for:
* Amino acids
* Coenzymes
* Fatty acids

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15
Q

What diseases have altered glycolysis?

A
  • Diabetes
  • Cancer
  • Neurodegeneration
  • Immune diseases
  • Infection
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16
Q

What are the major pathways of glucose utilisation?

A
  1. Synthesis of structural polymers
  2. Storage
  3. Oxidation via pentose phosphate pathway
  4. Oxidation via glycolysis
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17
Q

How was glycolysis discovered?

A

Through work with yeast and muscle cells

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18
Q

What is the near universal pathway for glucose catabolism called?

A

Glycolysis

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19
Q

How many Cs does Pyruvate have?

A

3C

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20
Q

What biochemical processes in the cell were discovered as a result of studies on Glycolysis?

A

Role of ATP & Phosphorylated compounds

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21
Q

How many enzymes take part in Glycolysis?

A

10

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22
Q

What is the enzyme that converts Glucose to Glucose 6-phosphate?

A

Hexokinase

1st enzyme in Glycolysis

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23
Q

What happens in the “Preparatory” phase of Glycolysis?

A

Phosphorylation of glucose and its conversion to glyceraldehyde 3-phosphate

24
Q

What happens in the “Pay-Off” phase of Glycolysis?

A

Oxidative conversion of glyceraldehyde 3-phosphate to pyruvate and the coupled formation of ATP and NADH

25
Q

What occurs in the “Preparatory” phase of Glycolysis in terms of energy?

A

Energy is invested in the form of 2 ATP

Steps 1 and 3

26
Q

What occurs in the “Pay-Off” phase of Glycolysis in terms of energy?

A

Energy is produced in the form of 4 ATP and 2 NADH

  • NADH - Step 6
  • ATP - Steps 7 and 10
27
Q

What happens in Step 1 of Glycolysis?

A
  • Glucose is phosphorylated on position 6
  • ATP donates the phosphate
28
Q

Which enzyme is involved in Step 1 of Glycolysis?

A

Hexokinase

29
Q

Why does Hexokinase need Mg2+ to add a phosphate group to glucose in Step 1 of Glycolysis?

A

Mg2+ shields the terminal phosphate of ATP from hydrolysis by H2O to enable nucleophilic attack by OH on C6 of glucose

30
Q

What happens in Step 3 of Glycolysis?

A

Fructose 6-phosphate is phosphorylated to Fructose 1-6-bisphosphate

  • Committed step in Glycolysis
  • ATP donates a phosphate
31
Q

Which enzyme is involved in Step 3 of Glycolysis?

A

Phosphofructokinase-1

Major regulatory enzyme for Glycolysis

32
Q

What happens in Step 6 of Glycolysis?

A

2x Glyceraldehyde 3-phosphates are oxidased and phosphorylated to 1,3-bisphosphoglycerate

33
Q

How is energy produced in Step 6 of Glycolysis and how much energy is produced?

A

Oxidation transfers electrons from 2x Glyceraldehyde 3-phosphate to 2NAD –> 2NADH

34
Q

What enzyme is involved in Step 6 of Glycolysis?

A

Glyceraldehyde 3-phosphate dehydrogenase

Removes H+

35
Q

What happens in Step 10 of Glycolysis?

A

2x Phosphoenolpyruvate is dephosphorylated to yield 2x Pyruvate & 2ATP

36
Q

Which enzyme is involved in Step 10 of Glycolysis?

A

Pyruvate Kinase

37
Q

What does a kinase enzyme do?

A

Add phosphoryl groups to substrates

38
Q

What is a substrate level phosphorylation?

A

A reaction that results in the production of ATP by the transfer of a phosphate group from a substrate

39
Q

What are the regulatory enzymes in Glycolysis?

A
  • Hexokinase
  • Phosphofructokinase
  • Pyruvate kinase
40
Q

Does Glycolysis need oxygen?

A

No

41
Q

What are the THREE possible fates of Pyruvate?

A
  • 2x Ethanol + 2CO2
  • 2x Acetyl-CoA
  • 2x Lactate
42
Q

What is Pyruvate converted into in the presence of O2?

A

2x Pyruvate decarboxylated to 2x Acetyl-CoA

43
Q

What TWO molecules are Pyruvate converted to in the absence of O2?

A
  • Lactate
  • Ethanol
44
Q

Is Pyruvate oxidised or reduced when converted to lactate / ethanol?

A

Reduced

45
Q

Does NAD+ get regenerated for Step 6 of Glycolysis in the conversion of Pyruvate to lactate / ethanol?

A

Yes. Allows continuous Glycolysis to occur in absence of O2

46
Q

What organsims convert Pyruvate to ethanol?

A

Yeast

47
Q

What are the TWO enzymes called that convert Pyruvate to enthanol?

A
  • Pyruvate decarboxylase
  • Alcohol dehydrogenase
48
Q

Describe the reaction of converting Pyruvate to ethanol

A
  1. Pyruvate is decarboxylated
  2. Forms Acetaldehyde
  3. Hydrogen atoms from NADH + H+ convert Acetaldehyde to Ethanol
49
Q

What can’t vertebrates and lactic acid bacteria make ethanol from Pyruvate?

A

Pyruvate Decarboxylase is absent

50
Q

What is the enzyme called that produces Lactate from Pyruvate?

A

Lactate Dehydrogenase

51
Q

Describe the reaction of coverting Pyruvate to Lactate

A
  1. Lactate Dehydrogenase removes NADH + H+ make NAD+
  2. Pyruvate is converted lactate
52
Q

Describe what happens during anaerobic respiration in muscle during a sprint

A
  • O2 can’t get to muscle fast enough
  • Muscle switches to anaerobic glycolysis
  • Breaks down muscle glycogen stores to lactate for energy
  • Lactate enters the blood and goes to the liver
  • Lactate synthesises glucose in the liver
  • Glucose goes from the liver –> blood –> muscle to replenish glycogen
53
Q

Describe the potential importance of anaerobic respiration in cancer cells

A
  • Increased levels of glycolytic enzymes occur in cancer cells
  • Pyruvate kinase (PKM2) has reduced catalytic activity compared to PKM1
  • Allows cancer cells to keep using anaerobic glycolysis for energy, promoting proliferation
54
Q

Describe the potential importance of anaerobic respiration in immune cells

A

Immune cells “rewire” metabolism to use anaerobic glycolysis (Glucose to Lactate) even when O2 is present

55
Q

Where in the cells is Pyruvate converted to Acetyl-CoA?

A

Mitochondria

BC2002: Principles Of Metabolic Pathways (6 decks)

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