Chapter 3, Thermodynamics of Biological Systems Video Solutions, Biochemistry

Problem 1

An enzymatic hydrolysis of fructose- $1-P$
\[\text { Fructose- } 1-\mathrm{P}+\mathrm{H}_{2} \mathrm{O} \rightleftharpoons \text { fructose }+\mathrm{P}_{1}\]
was allowed to proceed to equilibrium at $25^{\circ} \mathrm{C}$. The original concentration of fructose-1-P was $0.2 \mathrm{M}$, but when the system had reached equilibrium the concentration of fructose-1-P was only $6.52 \times 10^{-5} \mathrm{M}$. Calculate the equilibrium constant for this reaction and the free energy of hydrolysis of fructose- $1-P$.

Matthew Hurlock

Numerade Educator

17:23

Problem 2

The equilibrium constant for some process $A=B$ is 0.5 at $20^{\circ} \mathrm{C}$ and 10 at $30^{\circ} \mathrm{C}$. Assuming that $\Delta H^{*}$ is independent of temperature, calculate $\Delta H^{\circ}$ for this reaction. Determine $\Delta G^{\circ}$ and $\Delta S^{\circ}$ at $20^{\circ}$ and at $30^{\circ} \mathrm{C}$. Why is it important in this problem to assume that $\Delta H^{\circ}$ is independent of temperature?

Susan Hallstrom

Numerade Educator

02:02

Problem 3

The standard-state free energy of hydrolysis for acetyl phosphate is
\[
\begin{aligned}
\Delta G^{\circ}=-42.3 \mathrm{kJ} / \mathrm{mol} \\
\text { Actyl-P }+\mathrm{H}_{2} \mathrm{O} \longrightarrow \text { acctate }+\mathrm{P}_{\mathrm{i}}
\end{aligned}
\]
Calculate the free energy change for acetyl phosphate hydrolysis in a solution of $2 \mathrm{m} M$ acctate, $2 \mathrm{m} M$ phosphate, and $3 \mathrm{n} M$ acetyl phosphate.

Adriano Chikande

Numerade Educator

02:52

Problem 4

Define a state function. Name three themodynamic quantities that are state functions and three that are not.

Daniel Kim

Numerade Educator

01:55

Problem 5

ATP hydrolysis at pH 7.0 is accompanicd by release of a hydrogen ion to the medium
\[\mathrm{ATP}^{6-}+\mathrm{H}_{2} \mathrm{O} \rightleftharpoons \mathrm{ADP}^{3-}+\mathrm{HPO}_{4}^{2-}+\mathrm{H}^{+}\]
If the $\Delta G^{\circ}$ for this reaction is $-30.5 \mathrm{kJ} / \mathrm{mol}$, what is $\Delta G^{*}$ (that is, the free energy change for the same reaction with all components, including $\mathrm{H}^{+},$ at a standard state of $1 \mathrm{M}$ )?

Kratika Bhadauria

Numerade Educator

01:35

Problem 6

For the process $A \equiv B, K_{c g}(A B)$ is 0.02 at $37^{\circ} \mathrm{C}$. For the process $\mathrm{B} \rightleftharpoons \mathrm{C}, K_{\mathrm{eq}}(\mathrm{BC})=1000$ at $37^{\circ} \mathrm{C}$
a. Determine $K_{\mathrm{rg}}(\mathrm{AC}),$ the equilibrium constant for the overall process $A \rightleftharpoons C,$ from $K_{c q}(A B)$ and $K_{c g}(B C)$
b. Determine standardstate free energy changes for all three processes, and $\mathrm{us}=\Delta G^{\circ}(\mathrm{AC})$ to determine $K_{\mathrm{rg}}(\mathrm{AC}) .$ Make sure that this value agrees with that determined in part a of this problem.

David Collins

Numerade Educator

10:54

Problem 7

Draw all possible resonance structures for creatine phosphate and discuss their possible effects on resonance stabilization of the molecule.

Anupa Sharad Medhekar

Numerade Educator

01:39

Problem 8

Write the equilibrium constant, $K_{\mathrm{eq}},$ for the hydrolysis of creatine phosphate and calculate a value for $K_{\mathrm{eq}}$ at $25^{\circ} \mathrm{C}$ from the value of $\Delta G^{\circ}$ in Table 3.3.

Hailey Tomashek

Numerade Educator

01:19

Problem 9

Imagine that creatine phosphate, rather than ATP, is the universal energy carrier molecule in the human body. Repeat the calculation presented in Section $3.8,$ calculating the weight of creatine phosphate that would need to be consumed each day by a typical adult human if creatine phosphate could not be recycled. If recycling of creatine phosphate were possible, and if the typical adult human body contained 20 grams of creatine phosphate, how many times would each creatine phosphate molecule need to be turned over or recycled each day? Repeat the calculation assuming that glycerol- 3 phosphate is the universal energy carrier and that the body contains 20 grams of glycerol- 3 phosphate.

Ummatul Choudary

Numerade Educator

02:32

Problem 10

Calculate the free energy of hydrolysis of ATP in a rat liver cell in which the ATP, ADP, and $P$, concentrations are $3.4,1.3,$ and $4.8 \mathrm{m} M$ respectively.

Prashant Bana

Numerade Educator

01:47

Problem 11

Hexokinase catalyzes the phosphorylation of glucose from ATP, yielding glucose- $6-P$ and ADP. Using the values of Table $3.3,$ calculate the standard-state free energy change and equilibrium constant for the hexokinase reaction.

Hailey Tomashek

Numerade Educator

04:03

Problem 12

Would you expect the free energy of hydrolysis of acetoacetylcoenzyme A (see diagram) to be greater than, equal to, or less than that of acetyl-coenzyme A? Provide a chemical rationale for your answer.

Eric Goldman

Numerade Educator

01:04

Problem 13

Consider carbamoyl phosphate, a precursor in the biosynthesis of pyrimidines:
Based on the discussion of high-energy phosphates in this chapter, would you expect carbamoyl phosphate to possess a high free energy of hydrolysis? Provide a chemical rationale for your answer.

John Nicolle

Numerade Educator

02:15

Problem 14

You are studying the various components of the venom of a poisonous lizard. One of the venom components is a protein that appears to be temperature sensitive. When heated, it denatures and is no longer toxic. The process can be described by the following simple equation:
\[
\mathbf{T}(\text { toxic }) \rightleftharpoons \mathrm{N} \text { (nontoxic) }
\]
There is only enough protein from this venom to carry out two equilibrium measurements. At $298 \mathrm{K}$, you find that $98 \%$ of the protein is in its toxic form. However, when you raise the temperature to $320 \mathrm{K},$ you find that only $10 \%$ of the protein is in its toxic form.
a. Calculate the equilibrium constants for the T to N conversion at these two temperatures.
b. Use the data to determine the $\Delta H^{\circ}, \Delta S^{\circ},$ and $\Delta G^{\circ}$ for this process.

Stephen Ho

Numerade Educator

01:53

Problem 15

Consider the data in Figures 3.3 and $3.4 .$ Is the denaturation of chymotrypsinogen spontaneous at $58^{\circ} \mathrm{C}$, And what is the temperature at which the native and denaturated forms of chymotrypsinogen are in equilibrium?

Manik Pulyani

Numerade Educator

00:31

Problem 16

Consider Tables 3.1 and $3.2,$ as well as the discussion of Table 3.2 in the text, and discuss the meaning of the positive $\Delta C_{p}$ in Table 3.1

Nicole Mabante

Numerade Educator

04:39

Problem 17

The difference between $\Delta G^{\circ}$ and $\Delta G^{\circ \prime}$ was discussed in Section 3.3 Consider the hydrolysis of acetyl phosphate (Figure 3,12 ) and determine the value of $\Delta G^{\circ}$ for each of this reaction at pH $2,7,$ and
12. The value of $\Delta G^{\circ \prime}$ for the enolase reaction (Figure 3.13 ) is $1.8 \mathrm{kJ} / \mathrm{mol} .$ What is the value of $\Delta G^{\circ}$ for enolase at $\mathrm{pH} 2,7,$ and $12 ?$ Why is this case different from that of acetyl phosphate?

Ronald Prasad

Numerade Educator

01:53

Problem 18

What is the significance of the magnitude of $\Delta G^{\circ \prime}$ for ATP in the calculations in the box on page 67 ? Repeat these calculations for the case of coupling of a reaction to 1,3 bisphosphoglycerate hydrolysis to see what effect this reaction would have on the equilibrium ratio for components $A$ and $B$ under the conditions stated on this page.

Dr. Bridgette Drummond

Numerade Educator

03:13

Problem 19

The hydrolysis of 1,3 -bisphosphoglycerate is favorable, due in part to the increased resonance stabilization of the products of the reaction. Draw resonance structures for the reactant and the products of this reaction to establish that this statement is true..

Ramesh Singh

Numerade Educator

02:26

Problem 20

The acyl-Co.A synthetase reaction activates fatty acids for oxidation in cells:
\[
\mathrm{R}-\mathrm{COO}^{-}+\mathrm{CaASH}+\mathrm{ATP} \longrightarrow \mathrm{R}-\mathrm{COSCOA}+\mathrm{AMP}+\text { pyrophosphate }
\]
The reaction is driven forward in part by hydrolysis of ATP to AMP and pyrophosphate. However, pyrophosphate undergoes further cleavage to yield two phosphate anions. Discuss the energetics of this reaction both in the presence and absence of pyrophosphate cleavage.

Shazia Naz

Numerade Educator