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Ant
on FreezingBlue Flashcards.
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The first two laws of thermodynamics/bioenergetics
- First law - Energy is always conserved
- Second law - Entropy always increases
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Gibbs free energy equation & units
ΔG = ΔH - TΔS
J mol -1- ΔH -
J mol -1- T - °
K - ΔS -
J K mol -1
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What is Gibbs free energy?
Energy available to do work
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What is entropy
Measure of randomness of a system
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How does ΔG relate to ΔG°
ΔG = ΔG° + RT ln{[C]c[D]d/([A]a[B]b)}
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When does ΔG = ΔG°
When the equilibrium ratio = 1
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Equation for Keq
Keq = [C]c[D]d/([A]a[B]b)
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What are transformed standard constants?
- Constants used in Chemistry of Physics that have been transformed for Biochemistry
- ΔG'°, K'eq
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What are some requisites for transformed standard constants?
Invarient H2O, H+ or Mg2+
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Is ΔG constant?
No, it depends on product/reaction concentrations
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Energy coupling
Δ G'°Total = Δ G1'° + Δ G2'°
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What is an example of energy coupling?
Most reactions involving ATP
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Hexokinase
Phosphorylates glucose on carbon 6
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Esters
Stable products from reactions between a carboxylic acid and an alcohol
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Anhydride
- High energy bonds formed from two carboxylic acids eliminating water
- Easily hydrated (hydrolysis)
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ATP phosphate bonds
- Beta and Gamma - Phosphoanhydride
- Alpha - Phosphoester
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Why are resonance structures stabillizing?
They minimize local charges
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How does Mg2+ assist ATP hydrolysis
It partially shields the negative charges and causes a conformational change
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High group transfer potential
Associated with high energy bonds
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What is pyrophosphate? Why is it useful?
- p~p
- It is useful because it's cleavage from ATP is irreversible (used in RNA polymerase)
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Why are ATP analogues useful?
- Freeze coupled mechanisms to examine them
- Freeze ATP hydrolyzing enzymes to examine them
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Is polyphosphate ( ~P~P~P~P~P~P~) found in cells?
Yes, as energy storage or a chelating agent
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What enzyme produces polyphosphate?
- polyphosphate kinase-1
- ATP + polyPn <--(mg2+)--> ADP + polyPn+1
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