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From Flashcardlet > Biochemistry: Bioenergetics > Flashcards

Biochemistry: Bioenergetics Flashcards

0
Q

Anabolic reactions

A

Utilize ATP in the synthesis of marcomolecules, muscle contraction, active transport, etc

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1
Q

Catabolic reactions

A
  • Generate ATP by oxidizing substrates
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2
Q

Structure of ATP

A

Adenine + ribose + 3 phosphates linked by phosphoanhydride bonds

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3
Q

Under oxidative conditions, pyruvate is

A

oxidized to Acetyl CoA in the mitochondria by pyruvate dehydrogenase complex

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4
Q

Pyruvate Dehydrogenase Complex

A
  • Exists in mitochondrial matrix
  • Oxidizes pyruvate –> acetyl coA + CO2
    • Also generates NADH that can be oxidized further in the mitochondria
  • Consists of 3 catalytic subunits
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5
Q

Pyruvate (structure and facts)

A
  • Alpha keto carboxylic acid

- Is glucogenic

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6
Q

Highly exergonic reactions are __ in the cell

A
  • Irreversible
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7
Q

Gibbs Free Energy

A

Chemical energy available to do work (energy comes from electrons)

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8
Q

Structure of Coenzyme A

A
  • consists of:
    • Phospho adenosine nucleotide
    • SH group
    • Panthetheine (vitamin B)
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9
Q

General function of CoA

A
  • Carrier of other molecules in the cell

- Cannot be transported across membranes because of the highly charged phosphate groups that lack specific transporters

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10
Q

Pyruvate –> Acetyl CoA

A
  • Carried out by pyruvate dehydrogenase complex
  • Highly exergonic (irreversible)
  • Occurs in mitochondria
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11
Q

Cofactors involved in pyruvate dehydrogenase rxn

A 
FAD
NAD
TPP
CoA
Lip
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12
Q

Structure of NAD and NADH:

A
  • Carrier of electrons

- Nicotinamide ring that carries 2 electrons and 1 H

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13
Q

FAD and FADH2 structure

A
  • Carry 2 electrons and 2 Hydrogens
  • Found in cytoplasm and mitochondria
  • Used by pyruvate dehydrogenase
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14
Q

First electron acceptor in the ETC

A

NAD (NADH Dehydrogenase)

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15
Q

Regulation of pyruvate dehydrogenase

A

Products of reaction (NADH and Acetyl CoA) inhibit the E1 subunit
Pyruvate dehydrogenase kinase phosphorylates E1 subunit in 3 different places to inactivate it

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16
Q

Pyruvate Dehydrogenase Phosphatase (role and regulation)

A
  • Dephosphorylates the E1 subunit of Pyruvate Dehydrogenase to activate it
  • Is activated by Mg2+ and Ca2+
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17
Q

Pyruvate dehydrogenase kinase (role and regulation)

A
  • Phosphorylates E1 subunit of pyruvate dehydrogenase to inactivate it
  • Is activated by NADH and acetyl CoA
  • Is inactivated by Pyruvate, NAD, and CoA
  • Also regulated by various hormones and tyrosine kinases in cells
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18
Q

Major function of Krebs Cycle

A
  • To oxidize Acetyl CoA and produce NADH and FADH2 that is used to generate ATP in the ETC
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19
Q

Each molecule of Acetyl-CoA generates:

A

3 molecules of NADH
1 molecule of FADH2
1 molecule of GTP

The two carbons in the Acetyl group are oxidized to CO2

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20
Q

The CoA that is released in the Krebs Cycle is used to

A

regenerate more Acetyl-CoA by the pyruvate dehydrogenase complex

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21
Q

GTP in Krebs Cycle is formed from

A

Succinyl CoA hydrolysis

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22
Q

NADH in Krebs Cycle are formed from

A

Isocitrate
Alpha-ketoglutarate
Malate dehydrogenases

23
Q

Reducing equivalents (electrons and Hs) from ___ and ___ enter the ___ and generate __

A

NADH and FADH2 enter ETC and are used to generate 9 ATPs

24
Q

Krebs Cycle occurs in the

A

Mitochondrial matrix

25
Q

ETC occurs in

A

the inner mitochondrial membrane

26
Q

Regulation of Krebs Cycle

A
  • Availability of substrates (Acetyl CoA)
  • Availability of O2
  • Need for energy (ATP)
  • Allosteric regulation of enzymes
27
Q

Allosteric regulator of Citrate Synthase

A

Inhibited by Succinyl CoA

28
Q

Structure of mitochondria

A
  • Permeable outer membrane

- Impermeable inner membrane

29
Q

Major source of NADH in cytoplasm comes from

A

Glycolysis

30
Q

Mitochondrial Shuttle Systems (2 types)

A

Malate-Aspartate shuttle

Glycerol-3-Phosphate shuttle

31
Q

Overall function of Mitochondrial shuttle systems

A
  • Takes Hs from NADH and FADH2 and transports them (doesn’t carry NADH or FADH2 itself)
32
Q

Primary donor of hydrogens and electrons in ETC

A
  • NADH
33
Q

Final acceptor of hydrogens and electrons in ETC

A

O2

34
Q

ETC: Complex I

A
  • NADH Dehydrogenase
  • Transfers 2 Hydrogens and 2 electrons to CoQ via enzyme-bound FMN and Fe-S centers
  • Pumps 4 protons into intermembrane space
35
Q

FMN (structure)

A
  • Carry 2 electrons and 2 hydrogens
36
Q

FeS proteins

A
  • Found in complexes I, II, and III
  • Carry 1 electron at a time
  • Ubiquitous
37
Q

Succinate Dehydrogenase

A
  • Part of Krebs cycle and ETC
  • Donates 2 Hs and 2 electrons to enzyme-bound FAD
  • Does NOT pump protons into intermembrane space
38
Q

Coenzyme Q

A
  • Carries 2 hydrogens and 2 electrons (may carry 1 electron)
  • Ubiquitous
  • Receives electrons and hydrogens from flavin-linked enzymes
  • Donates electrons to complex III
  • First common intermediate for all oxidative metabolic pathways
39
Q

Complex III (cytochrome bc1)

A
  • Cytochrome bc1- cytochrome c reductase
  • Cyt bc:
    • 1receives 2 electrons from CoQ, one at a time,
    • Has 3 heme groups
    • Pumps 4 protons into the intermembrane space
    • Cyt bc 1 donates electrons to Cyt c via FeS protein
40
Q

Cytochrome always has

A

Heme attached to it

41
Q

Cyt bc1 has

A

3 heme groups

42
Q

Cytochrome c (structure and function)

A
  • Protein that is loosely bound to outer surface of the inner mitochondrial membrane
  • Transfer electrons between complexes III and IV
  • Is covalently bound to protein by C-S bond
  • Transfers 1 electron at a time
  • Involved in apoptosis
43
Q

Heme A

A
  • Found in Complex IV

- Carries 1 electron at a time

44
Q

Complex IV

A
  • Contains hemes and 2 Cu ions
  • Accepts 4 electrons from cytochrome c and 4 Hs in the matrix
  • Binds O2 and reduces it to water
  • Pumps 4 protons into intermembrane space
45
Q

ATP synthase

A
  • Driven by electrochemical (proton) gradient
  • Central gamma subunit rotates as a result of the gradient
  • ATP synthesis is catalyzed by beta subunits of F1 ATP synthase
  • c subunit and F1 alpha subunits hold beta subunits stationary
46
Q

Rotation of ATP synthase

A

T (tight) conformation: binds ATP tightly
L (loose) conformation: binds ADP and Pi loosely
O (open) conformation: does not bind nucleotide

47
Q

ATP synthesis is coupled to

A

Redox reactions

48
Q

Acetyl coA vs pyruvate

A

Pyruvate is glucogenic

Acetyl coA is ketogenic

49
Q

Function of Acetyl coA

A
  • Krebs cycle substrate

- fatty acid synthesis

50
Q

TPP (Thiamine Pyrophosphate)

A
  • Carrier of the 2-carbon fragment generated by decarboxylation of pyruvate
51
Q

Lipoic Acid

A

Carirer of the acetyl group formed by Pyruvate Dehydrogenase

52
Q

NAD and NADP are found in

A

cytoplasm of mitochondria

53
Q

NADPH vs. NAD (differences)

A

NADPH is used in biosynthetic reactions

NAD is used in catabolic reactions

54
Q

ETC Complexes that pump protons across the inner membrane

A

Complexes I, III, and IV

55
Q

Purpose of shuttle transport systems

A
  • Transports reducing equivalents generated in the cytoplasm across the inner mitochondrial membrane.
  • Provides cytoplasmic reducing equivalents to the ETC and generate ATP

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