Unit 4: Chapter 18 Flashcards

1
Q

Is Digestive System Catabolic or Anabolic process?

A

Ctabolic: break down to smaller molecules

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2
Q

Stages of Digestive System

A
  1. Polymers broken down into smaller subunits in digestive system
  2. Simple subunits are further broken down to activated carrier, Acetyl CoA
  3. Acetyl CoA is oxidized to CO2, coupled to production of large amounts of ATP
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3
Q

Pyruvate Dehydrogenase Complex

A

Forming acetyl coenzyme A from pyruvate

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4
Q

How is pyruvate dehydrogenase complex regulated?

A

phosphorylation and dephosphorylation

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5
Q

Acetyl CoA (Coenzyme A)

A
  • active carrier carrying acetyl groups
  • fuel for citric acid cycle
  • 2 carbon acetyl unit
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6
Q

Under aerboic conditions (O2), ______ enters ________ where it is converted to acetyl CoA

A

pyruvate; mitochondria

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7
Q

Where is acetyl CoA formed?

A

Mitochondrial matrix via pyruvate dehydrogenase complex
Acetyl CoA cannot enter two membrane of mitochondria

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8
Q

Structure of Acetyl CoA

A

ADP, hydrocarbon tail, acetyl group (acetyl group contains thioester bond which is very high energy rich bond)

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9
Q

SH group forms ____ bond with acetyl CoA

A

thioester

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10
Q

Thioester bonds

A

Have high standard free energy of hydrolysis so will release energy and can donate their acyl group to a variety of acceptors

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11
Q

Pyruvate dehydrogenas complex

A

Preparing citric acid cycle with product of acetyl CoA
5 enzymes in mitochondrial matrix enzyme
Links glycolysis to citric acid cycle

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12
Q

What are E1, E2, E3 involved in pyruvate dehydrogenase complex?

A

Involved in converting pyruvate to acetyl CoA (catalytic, break down)

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13
Q

Regulation of pyruvate dehydrogenase complex

A
  1. Pyruvate dehydrogenase kinase: add phosphate to inactivate
  2. Pyruvate dehydrogenase phosphatase: removes phosphate to activate
  3. Energy charge
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14
Q

Overall reaction equation of pyruvate dehydrogenase complex

A

pyruvate + CoA + NAD+ –> acetyl CoA + CO2 + NADH + H+

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15
Q

Is pyruvate dehydrogenase complex reversible or irreversible reaction?

A

Irreversible reaction
Acetyl CoA cannot be made into pyruvate and glucose

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16
Q

Pyruvate dehydrogenase complex (E1)
Prosthetic group:
Reaction catalyzed:

A

Prosthetic group: TPP
Reaction catalyzed: Oxidative decarboxylation of pyruvate

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17
Q

Dihydrolipoyl tranacetylase (E2)
Prosthetic group:
Reaction catalyzed:

A

Prosthetic group: Lipoamide
Reaction catalyzed: Transfer of acetyl group of CoA

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18
Q

Dihydrolipoyl dehydrogenase (E3)
Prosthetic group:
Reaction catalyzed:

A

Prosthetic group: FAD
Reaction catalyzed: Regeneration of oxidized form of lipoamide

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19
Q

Prosthetic group

A

Tightly attached to enzyme and help catalyst
Do not undergo changes and must be returned back to original state

20
Q

Synthesis of acetyl coenzyme A from pyruvate requires

A

5 enzymes and 3 coenzymes

21
Q

Synthesis of acetyl conenzyme A consists of 3 steps

A
  1. decarboxylation
  2. oxidation
  3. transfer to CoA
22
Q

Step 1 of synthesis of acetyl coenzyme A: Decarboxylation

A
  • slowest step, rate limiting step
  • E1 catalyzes
  • E1 combines with ionized form of coenzyme TPP
  • Pyruvate combines with TPP and is then decarboxylated to yield hydroxyethyl group
  • C1 of pyruvate released as CO2
  • Productis hydroxyethyl TPP
23
Q

Thiamine Pyrophosphate (TPP)

A

Conezyme derived from vitamin thiamine and plays a role in decarboxylation of pyruvate
Protesthetic group of E1

24
Q

Step 2 of synthesis of acetyl coenzyme A: Oxidation

A
  • Hydroxyethyl group attached to TPP is oxidized to form acetyl group while being simutaneously transferred to a sulfur atom of the reduced form of lipoamide
  • E2 inserts lipamide arm of lipoamide to E1
  • E1 catalyzes transfer of acetyl group to lipoamide
  • Acetylated arm leaves E1 and enters E2
  • Disulfide group of lipoamide is reduced to its disulfhydryl form
  • Reaction is catalyzed by E1 and yields acetyl lipoamide
25
Q

Step 3 of synthesis of acetyl coenzyme A: Formation of Acetyl CoA

A
  • E2 catalyzes the transfer of acetyl group from acetyl lipoamide to conezyme A to form acetyl CoA
  • E3 catalyzes for lipoamide to return back to disulfide (oxidized) form since prosthetic groups must return back to original state
  • 2 electrons are transfered to an FAD and reduced to FADH2
  • 2 electrons are transfered from FADH2 to NAD+ and then reduced to NADH
26
Q

Hihg concentration of NADH and acetyl CoA inform the enzyme that

A
  • energy needs of the cell have been met or that enough acetyl CoA and NADH have been produced from fatty acid degradation
  • No need to metabolize pyruvate to acetyl CoA
27
Q

During your exercise the concentration of ____ and ____ will increase

A

ADP; pyruvate

28
Q

During you exercise, muscle contraction consumes _____ and _____ is converted to _____ to meet energy demands

A

ATP; Glucose; pyruvate

29
Q

Both ___ and ____ activate dehydrogenase by inhibiting pyruvate dehydrogenase kinase

A

ADP; pyruvate

30
Q

Phosphotate is stimulated by ____

A

Ca2+

31
Q

Ca2+

A
  • A signal that initiates muscle contraction
  • Rise in Ca2+ activates the phosphatase, enhancing pyruvate dehydrogenase activity
32
Q

What enzyme is this: transfers a 2 carbon unit to TPP and releases CO2 and forms acetyl lipoamide?

A

Pyruvate dehydrogenase (E1)

33
Q

What enzyme is this: transfers the 2 carbon acetyl unit to lipoic acid and then to enzyme A (formation fo acetyl Coa)?

A

Dihydrolipoyl transacetylase (E2)

34
Q

What enzyme is this: reoxidizes lipoic acid and reduces NAD+ to NADH?

A

Dihydrolipoyl dehydrogenase (E3)

35
Q

Pyruvate dehydrogenase kinase

A

For regulation of pyruvate dehydrogenase complex
Phosphorylates E1 for complex to be inhibited

36
Q

Pyruvate dehydrogenase phosphatase

A

For regulation of pyruvate dehydrogenase complex
Removes phosphate from E1 so complex activated

37
Q

Coenzymes involved in Pyruvate dehydrogenase complex

A

TPP, lipoamide, FAD, NAD+, conenzyme A

38
Q

____ impairs activity of pyruvate dehydrogenase componet of pyruvate dehydrogenase complex

A

Lack of TPP

39
Q

__ and ___ are toxic because of these chemicals bind to lipoci acid coenzyme of dihydrolipoyl dehydrogenase, inhibiting activity of this enzyme

A

Arsenite and Mercury

40
Q

Advantages of Multienzyme Complex

A
  1. The various stages of the reaction can take place more efficiently because reactants and enzymes are so close to each other; higher rate of rxn
  2. Coordinated control; regulatory controls can apply more efficiently
  3. Minumum side reaction
41
Q

2 Fates of Acetyl CoA

A
  1. Metabolism of citric acid cycle
  2. Incorporation into fatty acids
42
Q

The synthesis of _____ by the pyruvate dehydrogenase complex is key irreversible step in metabolism of glucose

A

acetyl CoA

43
Q

Which enzyme is key site of regulation for pyruvate dehydrogenase complex?

A

E1

44
Q

What can inhibit the pyruvate dehydrogenase complex?

A

ATP, acetyl CoA, NADH

45
Q

What can stimulate the pyruvate dehydrogenase complex?

A

ADP and pyruvate