Q: A reaction has $$\Delta G^\circ = -30\ \mathrm{kJ/mol} at$$ $$25^\circC. $$What is the equilibrium constant $$K_{eq}$$ for this reaction? (Use $$R = 8.314\ \mathrm{J/(mol\cdot K)}$$ and $$T = 298\ \mathrm{K})$$

$$K_{eq} = e^{\frac{30000}{8.314 \times 298}} \approx 1.8 \times 10^5$$

Q: A reaction in a cell has $$[ATP] = 15\ \mathrm{mM}$$, $$[ADP] = 1.5\ \mathrm{mM}$$, and $$[P_i] = 10\ \mathrm{mM}. $$The reaction is $$ATP \rightarrow ADP + P_i. $$What is the mass-action ratio $$Q$$ for this reaction?

$$Q = \frac{[ADP][P_i]}{[ATP]} = \frac{1.5 \times 10}{15} = 1$$

Question 1

Which of the following statements best describes the difference between configuration and conformation in biomolecules?

Accepted Answer

Configuration refers to the fixed spatial arrangement of atoms that can only be changed by breaking covalent bonds, while conformation refers to the spatial arrangement that can be changed by rotation around single bonds.

Question 2

Which of the following functional groups is present in both amino acids and nucleotides?

Accepted Answer

Amino group $$\mathrm{(-NH_2$)}$$

Question 3

A molecule contains a carbon atom bonded to four different substituents. Which of the following statements is true regarding this carbon atom?

Accepted Answer

It is a chiral center and can give rise to stereoisomers.

Question 4

Which of the following best explains why living organisms are not at equilibrium with their surroundings?

Accepted Answer

They maintain a dynamic steady state that requires constant energy input.

Question 5

Which of the following equations correctly represents the relationship between free energy change ($$\Delta G$$), enthalpy change ($$\Delta H$$), and entropy change ($$\Delta S) at $$absolute temperature $$T$$?

Accepted Answer

$$\Delta G = \Delta H - T\Delta S$$

Question 6

A reaction has $$\Delta G^\circ = -30\ \mathrm{kJ/mol} at$$ $$25^\circC. $$What is the equilibrium constant $$K_{eq}$$ for this reaction? (Use $$R = 8.314\ \mathrm{J/(mol\cdot K)}$$ and $$T = 298\ \mathrm{K})$$

Accepted Answer

$$K_{eq} = e^{\frac{30000}{8.314 	imes 298}} \approx 1.8 	imes 10^5$$

Question 7

Which of the following best describes the role of ATP hydrolysis in cellular metabolism?

Accepted Answer

ATP hydrolysis is highly exergonic and is often coupled to endergonic reactions to drive them forward.

Question 8

Which of the following is a correct statement about oxidation-reduction (redox) reactions in biological systems?

Accepted Answer

One reactant is oxidized (loses electrons) while another is reduced (gains electrons).

Question 9

Which of the following best explains why enzymes are essential for life?

Accepted Answer

They lower the activation energy of biochemical reactions, greatly increasing reaction rates.

Question 10

A reaction in a cell has $$[ATP] = 15\ \mathrm{mM}$$, $$[ADP] = 1.5\ \mathrm{mM}$$, and $$[P_i] = 10\ \mathrm{mM}. $$The reaction is $$ATP \rightarrow ADP + P_i. $$What is the mass-action ratio $$Q$$ for this reaction?

Accepted Answer

$$Q = \frac{[ADP][P_i]}{[ATP]} = \frac{1.5 	imes 10}{15} = 1$$

Question 11

Which of the following best describes the geometry of carbon bonding in methane ($$CH_4$$)?

Accepted Answer

Tetrahedral geometry with bond angles of approximately $$109.5^\circ$$

Question 12

Which of the following is NOT a bulk element essential to animal life and health?

Accepted Answer

Manganese ($$Mn)$$

Question 13

Which of the following best describes the relationship between $$\Delta G$$ and the spontaneity of a reaction?

Accepted Answer

A reaction is spontaneous if $$\Delta G is $$negative.

Question 14

Which of the following is a correct statement about the specificity of biological systems for stereoisomers?

Accepted Answer

Biological systems can distinguish between stereoisomers and often only utilize one specific isomer.

Question 15

Which of the following best describes the role of polysaccharides in living organisms?

Accepted Answer

They serve as fuel stores and structural components of cell walls.

Question 16

Which of the following is a correct statement about the standard free-energy change ($$\Delta G^\circ) of a $$reaction?

Accepted Answer

$$\Delta G^\circ = -RT \ln K_{eq}$$

Question 17

Which of the following best describes the difference between an open, closed, and isolated system in thermodynamics?

Accepted Answer

An open system exchanges both energy and matter with its surroundings; a closed system exchanges only energy; an isolated system exchanges neither.

Question 18

Which of the following is a correct example of a coupling reaction in metabolism?

Accepted Answer

The phosphorylation of glucose by hexokinase, coupled to ATP hydrolysis.

Question 19

Which of the following best describes the concept of the metabolome?

Accepted Answer

The entire collection of small molecules in a given cell under specific conditions.

Chemical Foundations of Biochemistry: Elements, Bonding, and Functional Groups

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