Biochemistry 2 Week 5

The following molecules participate in oxidation-reduction reactions EXCEPT

• FADH2

• NAD+

• plastoquinone

• ATP

ATP

Which of the following is true for an open system?

It allows for free exchange of matter and energy with the surroundings.

Which of the following is correct concerning the first law of thermodynamics in biological systems?

Pressure and volume do not change

Which of the following would be an example of decreasing entropy?

• flow of ions through a channel from higher ionic concentration to lower ionic concentration

• catabolic pathway

• anabolic pathway

• ice melting

• anabolic pathway

For the reaction: A + B  ↔ C + D, which of the following is correct?

K_eq = [C][D]/[A][B]

Which of the following differentiates the biochemical standard state from the standard state when discussing standard free energy changes?

• 1M concentration for all reactants and products

• Temperature of 298 K

• pH of 7

• Constant pressure of 1 atm

pH of 7

In which case will a reaction be spontaneous only above a certain temperature according to the Gibbs free energy equation?

ΔH > 0; ΔS > 0

Which of the following statements is correct?

• an endergonic reaction drives an exergonic reaction in living systems

• an exergonic reaction drives an endergonic reaction in living systems

• ATP is rarely used in coupled reactions

• the overall free energy of a coupled reaction is the difference of the free energies for the individual reactions

An exergonic reaction drives an endergonic reaction in living systems

For ATP (shown below), cleavage of the bond between __________ has the largest ΔG°′.

α phosphate and β phosphate

Reduced molecules become _____ upon donating an electron in a redox reaction

oxidized

Photosynthesis reactants

• sunlight

• CO2

• water

Photosynthesis products

• glucose

• O2

Which of the following statements about redox reactions is correct?

• A reduced compound becomes oxidized only when it acquires an electron from an oxidized compound

• An oxidized compound has fewer protons than its reduced counterpart

• A reduced compound has more carbon atoms than its oxidized counterpart

• A reduced compound becomes oxidized only when it transfers an electron to an oxidized compound

A reduced compound becomes oxidized only when it transfers an electron to an oxidized compound

The energy change in a system is related to the amount of heat transferred and work done. If there is no heat transferred, what is the magnitude of work in a system equal to?

energy change in the system (ΔE = E_final – E_initial)

Given the following reactions or reaction conditions, determine which are spontaneous.

• The hydrolysis of ATP under standard conditions: ATP ⇔ ADP + P_i 

• ΔGº' > 0

• ΔH < 0 and ΔS > 0

• K_eq = 10,000

• ΔGº' = +12.0 kJ/mol

• The hydrolysis of ATP under standard conditions: ATP ⇔ ADP + P_i

• ΔH < 0 and ΔS > 0

• K_eq = 10,000

Which of the following biochemical reactions are endergonic?

• Glutamate + NH₄⁺ + ATP ⇒ Glutamine + ADP + P_i ;   ΔG∘ΔG∘ = −16.3 kJ/mol

• ATP ⇒ ADP + P_i ;   ΔG∘ΔG∘ = −30.5 kJ/mol

• L-Malate + NAD⁺ ⇒ Oxaloacetate + NADH + H⁺ ;   ΔG∘ΔG∘ = +29.7 kJ/mol

• Acetyl-CoA + Oxaloacetate + H₂O ⇒ Citrate + CoASH + H⁺ ;   ΔG∘ΔG∘ = –32.2 kJ/mol

• Glutamate + NH₄⁺ ⇒ Glutamine;   ΔG∘ΔG∘ = +14.2 kJ/mol

• L-Malate + NAD⁺ ⇒ Oxaloacetate + NADH + H⁺ ;   ΔG∘ΔG∘ = +29.7 kJ/mol

• Glutamate + NH₄⁺ ⇒ Glutamine;   ΔG∘ΔG∘ = +14.2 kJ/mol

Which statement best describes the relationship between anabolic and catabolic pathways?

Catabolic pathways convert energy-rich compounds into energy-depleted compounds and are generally associated with breakdown, whereas anabolic pathways use compounds high in chemical energy for biosynthesis.

Which of the following reactions is anabolic?

• ATP ⇒ AMP + PP_i

• GTP ⇒ GDP + P_i

• sucrose ⇒  fructose + glucose

• glycerol + fatty acids  ⇒  a triacylglycerol

glycerol + fatty acids  ⇒  a triacylglycerol

The thermodynamic parameter entropy is a measure of

disorder

What are the units of entropy?

joule/mol*K

Given equal masses (the same number of moles of a compound), which phase of matter has the greatest entropy?

gas

At 25 °C, what is the K_eq for a reaction where ΔH∘ΔH∘ = –9.3 kJ/mol and ΔS∘ΔS∘ = 75.5 J/mol·K? 

375000

How are changes in enthalpy (H) and entropy (S), related to changes in free energy (G)?

ΔG=ΔH−TΔS

Given the following common reactions, which are entropically favored?

• 2 pyruvate ⇒ glucose

• 6CO₂ + 6H₂O ⇒ C₆H₁₂O₆ + 6O₂

• glucose6P ⇒ fructose6P

• ATP ⇒ ADP + P_i 

ATP ⇒ ADP + P_i 

At standard conditions, a biochemical reaction has a K_eq of 4,000. The reaction favors the

products

What is the change in free energy of this reaction, which has K_eq = 4,000?  

-20.5 kJ/mol

Given the following reaction,

     fructose-6-phosphate ⇔ fructose + P_i     ΔG° = –15.9 kJ/mol

What is the equilibrium constant under standard conditions? 

614

A reaction is always spontaneous if

the change in free energy, ΔG, is negative

Of the three thermodynamic quantities, ΔG, ΔH, ΔS, which is most useful for determining spontaneity of a reaction?

ΔG

At standard conditions, the equilibrium lies toward products for a given biochemical reaction. What is known about the change in free energy?

ΔG° is less than 0

The sodium–potassium ATPase hydrolyzes ATP to pump two K⁺ ions inside the cell and three Na⁺ ions out. This is an example of energy conversion in which the energy from ATP is converted to

• a chemical gradient across the cell membrane

• an electrical potential across the cell membrane

The ΔG°of ATP hydrolysis is –30.5 kJ/mol. Which of the following reactions are not spontaneous and could be driven by being coupled to hydrolysis of ATP (one ATP molecule per individual reaction)?

• dihydroxyacetone phosphate (DHAP) ⇔ glyceraldehyde-3-phosphate (GAP)  (+7.5 kJ/mol)

• glucose + P_i ⇔ glucose-6-phosphate  (+13.8 kJ/mol)

If a typical person hydrolyzes 100.0 mol of ATP per day, how much does this ATP weigh? (The molecular weight of ATP is 507 g/mol.)

50.7 kg