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BIOCH 200 > Metabolism > Flashcards

Metabolism Flashcards

1
Q

Two Major Purposes of Metabolism

A
  1. To obtain usable chemical energy from the environment
    - solar energy
    - consuming and breaking down nutrient molecules
  2. To make specific molecules that cells need to live and grow
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2
Q

Anabolic Pathways

A

Use energy to build larger molecules
Generally reductive
Electrons are used to make new bonds

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3
Q

Catabolic Pathways

A

Release energy
Generally oxidative
Electrons are removed as bonds are broken

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4
Q

Amphibolic Pathways

A

Operate in both catabolic and anabolic processes

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5
Q

Anapleurotic Reactions

A

Chemical reactions that form intermediates of a metabolic pathway

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6
Q

Fuel Sources

A 
Polysaccharides 
Triacylglycerol
Proteins
Nucleic Acids
-first 3 are the most significant
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7
Q

Storage of excess fuels

A

Carbs are stored as glycogen

Fatty acids are stored as fat in adipocytes

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8
Q

Reactions proceeding forward

A

When deltaG is negative
Exergonic
Spontaneous
Actual free energy determines if a reaction occurs

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9
Q

When deltaG>0

A

Reaction will not occur

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10
Q

When deltaG<0

A

Reaction will occur

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11
Q

When deltaG«0

A

Reaction is considered irreversible

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12
Q

When deltaG=0

A

Reaction is considered reversible
Close to equilibrium
Changes in concentration may change the direction of the reaction

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13
Q

Enzyme Regulation

A

Irreversible steps are usually regulated

Reversible steps are usually not regulated

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14
Q

Rate-Limiting Step in a Pathway

A

The irreversible, regulated reaction that determines the overall rate of the pathway

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15
Q

Product Inhibition

A

An enzyme is inhibited by the product of its reaction

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16
Q

Feedback Inhibition

A

An enzyme is inhibited by a metabolite further down the pathway

17
Q

Activation

A

An enzyme may be activated by a metabolite upstream
Ensures that the pathway in functioning in concert
-otherwise intermediates might accumulate
Feed-forward activation

18
Q

Reciprocal Regulation

A

Opposing pathways catalyze the reverse of another pathway
The irreversible reactions must be replaced or bypassed
Pathways are regulated to ensure that both do not operate simultaneously

19
Q

High Energy Intermediates

A

Compounds that contain usable chemical energy

-energy that can be recovered or used

20
Q

Types of High Energy Intermediates

A

Electron carriers: NADH, NADPH, FADH2, FMNH2
Nucleotide triphosphates: ATP, UTP, GTP
Thioesters

21
Q

Oxidative Reaction

A

Catabolism
Metabolites are oxidized
Cofactors are reduced
Typically NAD+, FAD

22
Q

Reductive Reaction

A

Anabolism
Metabolites are reduced
Cofactors are oxidized
Typically NADPH

23
Q

Nucleotides that Act as Electron Carriers

A

NAD+, NADP+, FAD

24
Q

Reduction Reactions of Cofactors

A

NAD+ + 2H+ + 2e- = NADH + H+

NADP+ + 2H+ + 2e- = NADPH + H+

FAD + 2H+ + 2e- = FADH2

25
Q

Which Nucleotides are Typically Cosubstrates (C-O)?

A

NAD+ and NADP+

26
Q

Which Nucleotide is Typically a Prosthetic Group (C-C)?

A

FAD

27
Q

FAD as a Prosthetic Group

A

As a prosthetic group, FADH2 must be reoxidized back into FAD for the next enzyme cycle to occur
In CAC, coenzyme Q is used to carry out this reoxidation

28
Q

What is the high-energy bond in ATP?

A

Because of phosphoanhydride bonds

29
Q

Phosphoanhydride Bonds

A

High energy bonds
deltaG= -32 for hydrolysis
deltaG= +32 for formation

30
Q

Why is ATP a high-energy molecule?

A

Decreased electrostatic repulsion
Resonance stabilization
-terminal phosphoryl group of ATP, inorganic phosphate
Solvent effects
-more interactions with water=favourable
These all contribute to free energy change

31
Q

Thioesters

A

High Energy Compounds

Similar to esters but with no delocalization

32
Q

ATP

A

Energy Currency
-common in multiple systems
-phosphoanhydride bond makes it high energy
Generated by Catabolism
-directly “substrate-level phosphorylation”
-via reoxidation of NADH/FADH2 “oxidative phosphorylation”
Used In
-driving unfavourable reactions (coupling)
-movement
-primary active transport (ion pumping)

33
Q

Coupling of Free Energies

A

Free energy changes for reactions are additive
A reaction with an overall unfavourable free energy change can occur when another favourable reaction occurs in concert
The combined reactions must have an overall deltaG<0 to be spontaneous

34
Q

Phosphate Transfer Potential

A

Free energies of hydrolysis for phosphate-containing compounds can be referred to as the phosphate transfer potential

BIOCH 200 (9 decks)

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