Lesson test: The price of everything

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The price of everything

1.[2p]
Why is the phrase "high energy phosphate bond" misleading?

Breaking a bond always costs energy, and what releases energy is the whole reaction, driven by charge relief, resonance and solvation of the products

Correct

ATP contains no phosphate bonds

The answer is: Breaking a bond always costs energy, and what releases energy is the whole reaction, driven by charge relief, resonance and solvation of the products

The bond is actually low in energy compared with a carbon to carbon bond

The answer is: Breaking a bond always costs energy, and what releases energy is the whole reaction, driven by charge relief, resonance and solvation of the products

The energy comes from the adenine ring rather than from the phosphates

The answer is: Breaking a bond always costs energy, and what releases energy is the whole reaction, driven by charge relief, resonance and solvation of the products

2.[3p]
With $Δ G^{\circ'} = - 30.5$ kJ/mol, $R T = 2.577$ kJ/mol and a reaction quotient of $5 \times 10^{- 4}$ , what is $Δ G$ for ATP hydrolysis in a cell, in kJ/mol?

CorrectNot quite: -50.1

3.[1p]
The extra free energy of ATP hydrolysis inside a cell, beyond the tabulated value, comes from the cell holding ATP far from its own equilibrium.

True

Correct

False

The answer is: True

4.[2p]
A human body holds about 50 g of ATP and turns over tens of kilograms a day. What follows?

ATP is a currency in continuous circulation, not a store, so supply must match demand moment by moment

Correct

ATP is an efficient long-term energy reserve

The answer is: ATP is a currency in continuous circulation, not a store, so supply must match demand moment by moment

Most ATP is never used

The answer is: ATP is a currency in continuous circulation, not a store, so supply must match demand moment by moment

The body must contain a large ATP reservoir somewhere

The answer is: ATP is a currency in continuous circulation, not a store, so supply must match demand moment by moment

5.[3p]
Why can an exergonic reaction not drive an endergonic one merely by being in the same solution?

Coupling requires a shared intermediate, so the two must be steps of one mechanism

Correct

The two reactions would have different temperatures

The answer is: Coupling requires a shared intermediate, so the two must be steps of one mechanism

Free energies of separate reactions cannot be added

The answer is: Coupling requires a shared intermediate, so the two must be steps of one mechanism

The endergonic reaction would run out of substrate first

The answer is: Coupling requires a shared intermediate, so the two must be steps of one mechanism

6.[2p]
Phosphorylating glucose with free phosphate has $Δ G^{\circ'} = + 13.8$ kJ/mol, and ATP hydrolysis has $- 30.5$ . What is $Δ G^{\circ'}$ for the hexokinase reaction, in kJ/mol?

CorrectNot quite: -16.7

7.[2p]
Match each cellular currency to what it carries.

ATP
NADH
NADPH
Acetyl-CoA
The proton gradient

an activated two-carbon unit
a transferable phosphate group
charge and concentration across a membrane
electrons for stripping off fuel
electrons for biosynthesis

Show the answer

ATP: a transferable phosphate group NADH: electrons for stripping off fuel NADPH: electrons for biosynthesis Acetyl-CoA: an activated two-carbon unit The proton gradient: charge and concentration across a membrane

8.[3p]
Why do some biosynthetic reactions split ATP to AMP and pyrophosphate, and then hydrolyse the pyrophosphate separately?

Select all that apply

Destroying a product by mass action makes the first step effectively irreversible

Correct

It is used at committing steps where reversal would be expensive

Correct

It releases twice as much energy per phosphate transferred

The answer is: Destroying a product by mass action makes the first step effectively irreversible, It is used at committing steps where reversal would be expensive

It avoids producing ADP, which the cell cannot recycle

The answer is: Destroying a product by mass action makes the first step effectively irreversible, It is used at committing steps where reversal would be expensive

9.[1p]
A negative $Δ G$ tells you a reaction will proceed at a useful rate.

True

The answer is: False

False

Correct

1.[2p] Why is the phrase "high energy phosphate bond" misleading?

2.[3p] With ΔG∘′=-30.5 kJ/mol, RT=2.577 kJ/mol and a reaction quotient of 5×10-4, what is ΔG for ATP hydrolysis in a cell, in kJ/mol?

3.[1p] The extra free energy of ATP hydrolysis inside a cell, beyond the tabulated value, comes from the cell holding ATP far from its own equilibrium.

4.[2p] A human body holds about 50 g of ATP and turns over tens of kilograms a day. What follows?

5.[3p] Why can an exergonic reaction not drive an endergonic one merely by being in the same solution?

6.[2p] Phosphorylating glucose with free phosphate has ΔG∘′=+13.8 kJ/mol, and ATP hydrolysis has -30.5. What is ΔG∘′ for the hexokinase reaction, in kJ/mol?

7.[2p] Match each cellular currency to what it carries.

8.[3p] Why do some biosynthetic reactions split ATP to AMP and pyrophosphate, and then hydrolyse the pyrophosphate separately?

9.[1p] A negative ΔG tells you a reaction will proceed at a useful rate.

1.[2p]
Why is the phrase "high energy phosphate bond" misleading?

2.[3p]
With $Δ G^{\circ'} = - 30.5$ kJ/mol, $R T = 2.577$ kJ/mol and a reaction quotient of $5 \times 10^{- 4}$ , what is $Δ G$ for ATP hydrolysis in a cell, in kJ/mol?

3.[1p]
The extra free energy of ATP hydrolysis inside a cell, beyond the tabulated value, comes from the cell holding ATP far from its own equilibrium.

4.[2p]
A human body holds about 50 g of ATP and turns over tens of kilograms a day. What follows?

5.[3p]
Why can an exergonic reaction not drive an endergonic one merely by being in the same solution?

6.[2p]
Phosphorylating glucose with free phosphate has $Δ G^{\circ'} = + 13.8$ kJ/mol, and ATP hydrolysis has $- 30.5$ . What is $Δ G^{\circ'}$ for the hexokinase reaction, in kJ/mol?

7.[2p]
Match each cellular currency to what it carries.

8.[3p]
Why do some biosynthetic reactions split ATP to AMP and pyrophosphate, and then hydrolyse the pyrophosphate separately?

9.[1p]
A negative $Δ G$ tells you a reaction will proceed at a useful rate.