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Amino Acids Quiz

• Friday

• Identify an amino acid:

– Full name

– Three letter code

– 1 letter code

– Net Charge at pH 7.4

• List Categories

– which aa are in each one

Thermodynamics review:Learning objectives:

• Compare and Contrast equilibrium and steady state

• Explain the difference between ΔG and ΔG˚’

• Predict the direction a reaction will proceed given

thermodynamic data.

Thermodynamic PrinciplesA Review

• Overall Thermodynamics – determines whether a physical process is possible

(i.e. spontaneous).

– provides no information about the rate of a physical

process.

• Gibbs Free Energy (G)G = H – TS

H = Enthalpy (Heat Content), S = Entropy (Disorder)

A ——> B

∆G = GB – GA

∆G = ∆H – T∆S

ΔG = ΔH – TΔS

Change in Enthalpy (∆H)

Exothermic: system releases energy

Endothermic: system gains energy

[energy required to break bonds] minus

[energy released from bonds formed]

Change in Entropy (∆S)

[Disorder of products] minus [Disorder of reactants]

Systems tend toward disorder

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Change in Free Energy (∆G)

Exergonic (−ΔG): spontaneous

Endergonic (+ΔG): requires input of energy

Indicator of Spontaneity

A + B ——> P + Q

∆G = G(P+Q) – G(A+B)

ΔH ΔS ΔG

− + −

− − − If ΔH>TΔS

+ + − If ΔH<TΔS

+ − +

Thermodynamics of the ReactionA + B ——> P + Q

Get into groups of 3

Take about 6 minutes

Work on critical thinking questions 1 and 2.

Take about 10 minutes

Work on critical thinking questions 3-6.

3

Standard Free Energy Change (ΔGo’)(Biochemical Standard State Conventions)

At equilibrium

25˚C

1 Atmosphere

pH 7.0

Actual Free Energy Change (ΔG)(based on conditions in the cell)

Usually At Steady State

Any temperature

~pH 7.4

Direction of the reaction

Free energy changes:

∆∆∆∆Go’ = standard

∆∆∆∆G = in the cell

∆∆∆∆G > 0

-Reverse (towards reactants)

∆∆∆∆G < 0

-Forward (towards products)

∆∆∆∆G = 0

-Equilibrium (i.e. Death)

Concentrations:

Keq = standard

[P]/[R] = in the cell

[P]/[R] > Keq

-Reverse (towards reactants)

[P]/[R] < Keq

-Forward (towards products)

[P]/[R] = Keq

-Equilibrium (i.e. Death)

For the reaction:

A � B Keq = 0.5

At equilibrium there are:

A. Equal amounts of products and reactants

B. More reactants

C. More products

The ∆�°�

= ?

A: < 0

B: 0

C: > 0

For the reaction:

A � B Keq = 0.5

If the P/R ratio = 0.8:

I. there is a higher [products] than [reactants]

II. there is a higher [reactants] than [products]

III. The reaction will proceed towards products

IV. The reaction will proceed towards reactants

A. I, III

B. I, IV

C. II, III

D. II, IV

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For the reaction:

A � B Keq = 2.3

If the P/R ratio = 1.7:

I. there is a higher [products] than [reactants]

II. there is a higher [reactants] than [products]

III. The reaction will proceed towards products

IV. The reaction will proceed towards reactants

A. I, III

B. I, IV

C. II, III

D. II, IV

Take about 5 minutes

Work on critical thinking questions 7-9.

Read the section provided on Steady state

And answer #10. A B

Thermodynamic Systems

Closed: Physical Chemistry (Equilibrium)

Open: Biochemistry (Steady-State)

Inputs and Outputs

A B

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How is steady state the same as equilibrium?

I. rate of the forward reaction = rate of the

backwards reaction

II. Concentrations of reactants and products are

unchanging

III. Reactants and products are continuously being

made

A. I

B. II

C. III

D. I, III

E. II, III