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Biochemistry > Q&A > Flashcards

Q&A Flashcards

1
Q

The rate-limiting step in glycolysis is catalysed by:

a) hexokinase
b) phosphofructokinase-1
c) glyceraldehyde phosphate dehydrogenase
d) phosphoglycerate kinase
e) pyruvate kinase

A

B - phosphofructokinase-1

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2
Q

Which of the following statements about the beta oxidation of fatty acids is INCORRECT?

a) Fatty acids are transported into the mitochondria via the carnitine carrier
b) In a series of four enzymatic steps, the fatty acid chain is shortened by 2 carbon atoms
c) In the two oxidation steps, two molecules of NADH are formed
d) The reduced co-enzymes are re-oxidised in the mitochondrial electron transport chain
e) High rates of fatty acid degradation can inhibit glycolysis

A

C - In the two oxidation steps, two molecules of NADH are formed

(Because in beta oxidation 1 FADH2 and 1 NADH is formed)

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3
Q
  1. The conversion of myristoyl-CoA (14:0) to lauryl-CoA (12:0) and 1 mol of acetyl-CoA by the β-oxidation pathway results in the net formation of:

a) 1 FADH2 and 1 NADH
b) 1 FADH2 and 1 NADPH
c) 1 FADH2, 1 NADH, and 1 ATP
d) 2 FADH2 and 2 NADH
e) 2 FADH2, 2 NADH, and 1 ATP

A

A - 1 FADH2 and 1 NADH

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4
Q

During fatty acid synthesis, what molecule is directly added to fatty acid chains on the fatty-acid synthase complex?

a) Malonyl-CoA
b) Acetyl-CoA
c) Pyruvate
d) Palmitoyl-CoA
e) Citrate

A

A - Malonyl-CoA

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5
Q

How does uncoupling protein 1 (thermogenin) disrupt the ETC?

A

It works essentially the same as DNP but it’s our body’s natural way of producing heat in brown adipose tissue (which has a high mitochondria concentration)

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6
Q

How does DNP (2,4-dinitrophenol) disrupt the ETC?

A
  • Disrupts the H+ gradient by binding to the H+ and transporting it across the membrane (DNP is lipid soluble)
  • Negates ATP synthase so no ATP production. NRG lost through dissipation of heat = fatal hyperthermia
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7
Q

How does cyanide disrupt the ETC?

A
  • It inhibits complex 4 (cytochrome oxidase).
  • Same electronic structure as oxygen. Cytochrome is a haem type molecule.
  • Binds to Fe atom & destroys its redox potential

… therefore = inhibition of complex 4

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8
Q

How does oligomycin disrupt the ETC?

A
  • It inhibits ATP synthase
  • Inhibits F0 and so the flow of H+ is prevented.

… therefore = No ATP synthesis

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9
Q

What are the 3 classes of inhibitors of the electron transport chain?

A
  1. Ones that block the flow of electrons
  2. Ones that block ATP synthase function
  3. Ones that uncouple electron transport & ATP synthesis by destroying the proton gradient
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10
Q

In proteins, which amino acid complexes with the iron-sulfur clusters?

A

Cysteine

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11
Q

Where does fatty acid catabolism occur?

A

Fatty acid to fatty acyl CoA in the cytoplasm

Fatty acyl transferase 1 & 2 transport Fatty acyl CoA to mitochondrial matrix and the rest occurs in the mitochondrial matrix.

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12
Q

Where does fatty acid synthesis occur?

A

In the cytoplasm - mainly in the liver.

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13
Q

How many ATPs do you get when 1 mol of NADH from glycolysis is transported to the ETC via malate-aspartate shuttle?

A

2.5 ATP

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14
Q

How many ATPs do you get when 1 mol of NADH from glycolysis is transported to the ETC via glycerol-3-phosphate shuttle?

A

1.5 ATP

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15
Q

True or false?

The citric acid cycle occurs in the cytoplasm.

A

False. It occurs in the mitochondrial matrix.

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16
Q

Name an aminase enzyme

A

Glutamine synthetase

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17
Q

Name a transaminase enzyme

A

Aminotransferase

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18
Q

Name 2 de-aminase enzymes

A

Glutaminase and glutamate dehydrogenase

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19
Q

What is the purpose of the Pentose Phosphate Pathway?

A
  • Alternative (parallel) pathway to glycolysis.
  • Synthesis of NADPH for:
    - Fatty acid synthesis
    - Cholesterol and nucleotide synthesis
  • Production of Ribose-5-phosphate for nucleic acids.
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20
Q

What happens to citrate when ATP levels are too high?

A

ATP levels high = TCA cycle off, citrate levels therefore accumulate, so citrate is exported from the matrix to the cytoplasm to be a shuttle for acetyl CoA (shuttles from matrix to the cytoplasm)

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21
Q

What are the names of the 3 ketone bodies?

A
  • Acetone
  • Acetoacetate
  • Beta hydroxybutyrate
22
Q

Which enzyme catalyzes step 4 (thiolytic cleavage) in beta oxidation of fatty acids?

A

Acyl CoA acetyl transferase (thiolase)

23
Q

Which enzyme catalyses step 3 (oxidation) of beta oxidation of fatty acids?

A

Beta hydroxyacyl-CoA dehydrogenase

24
Q

Which enzyme catalyses step 2 (hydration) of beta oxidation of fatty acids?

A

Enoyl-CoA hydratase

25
Q

Which enzyme catalyses step 1 (oxidation) of beta oxidation of fatty acids?

A

Acyl-CoA dehydrogenase

26
Q

Which hormones activate hormone sensitive lipase?

A

Glucagon & epinephrine

27
Q

What do phosphatases do?

A

Removes a phosphate group from a molecule

28
Q

What do kinases do?

A

Attach a phosphate group to a molecule

29
Q

What is a substrate level phosphorylation?

A

Transfer of a phosphate from a phosphorylated molecule to ADP, forming ATP. (so, phosphate group is REMOVED from molecule)

30
Q

What is a phosphorylation reaction?

A

When a phosphate group is ADDED to a molecule

31
Q

What is an isomerisation reaction?

A

One molecule is changed into another molecule with EXACTLY same atom, just different arrangement.

32
Q

What does glycogen synthase do?

A

In glycogen synthesis it makes alpha 1-4 bonds between glucose units

33
Q

What does branching enzyme do?

A

In glycogen synthesis it makes alpha 1-6 bonds between glucose units at the branch point

34
Q

What does glycogen phosphorylase do?

A

In glycogen breakdown it breaks alpha 1-4 bonds between glucose units. (breaks glycogen up into glucose subunits)

35
Q

What does debranching enzyme do?

A

In glycogen breakdown it breaks alpha 1-6 bonds between glucose units at the branch point

36
Q

What does hexokinase do?

A

Phosphorylates hexase sugars, forming hexase phosphates

37
Q

Which cofactors are in complex IV of the Electron Transport Chain?

A 
CytC
↓
CuA
↓
Heme A
↓
Heme A3
↓
CuB ---------> O2
38
Q

Which cofactors are in complex III of the Electron Transport Chain?

A 
CoQ
↓
CytB
↓
Fe-S
↓
CytC
39
Q

Which cofactors are in complex II of the Electron Transport Chain?

A

Fe-S
↓
CoQ

40
Q

Which cofactors are in complex I of the Electron Transport Chain?

A 
FmN-1
↓
Fe-S
↓
CoQ
41
Q

Define “cullular respiration”.

A

Process where chemical bonds of NRG rich molecules are converted into NRG usable forms for life processes

42
Q

What are the 3 enzymes that form the pyruvate dehydrogenase complex?

A

E1 –> Thiamine pyrophosphate
E2 –> Lipoic acid
E2 –> FAD

43
Q

At which step(s) in gluconeogenesis is ATP produced?

A

None.

44
Q

Which statement is NOT true of the citric acid cycle?

a) All enzymes of the cycle are located in the cytoplasm, except succinate dehydrogenase, which is bound to the inner mitochondrial membrane.
b) In the presence of malonate, one would expect succinate to accumulate.
c) Oxaloacetate is used as a substrate but is not consumed in the cycle.
d) Succinate dehydrogenase channels electrons directly into the electron transfer chain.
e) The condensing enzyme is subject to allosteric regulation by ATP and NADH.

A

B - In the presence of malonate, one would expect succinate to accumulate.

45
Q

Which statement about mammalian glycogen synthase is NOT correct?

a) It is especially predominant in liver and muscle.
b) The donor substrate molecule for glycogen synthesis is a sugar nucleotide.
c) The phosphorylated form of this enzyme is inactive.
d) This enzyme adds glucose units to the nonreducing end of glycogen branches.
e) This enzyme produces glycogen and glucose-1-phosphate as products.

A

E - This enzyme produces glycogen and glucose-1-phosphate as products.

46
Q

Where does the link reaction occur?

A

Mitochondrial matrix

47
Q

Where does FA synthesis occur?

A

Cytoplasm (mainly liver)

48
Q

Where does FA catabolism occur?

A

FA - Fatty Acyl CoA in cytoplasm.

Shuttled with carnitine acyl transferase 1 and 2 into mitochondrial matrix for beta oxidation.

49
Q

Where does glycolysis occur?

A

Cytoplasm

50
Q

Where does TCA occur?

A

Mitochondrial matrix

51
Q

Where does ETC occur?

A

Mitochondria

Biochemistry (2 decks)

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