Question 1

Which of the following statements best explains why carbon is the chemical foundation of life rather than silicon?

Accepted Answer

Carbon-to-carbon bonds are stronger and more stable than silicon-to-silicon bonds, allowing for more complex and stable biomolecules.

Question 2

Which of the following functional groups is correctly matched with its chemical property?

Accepted Answer

Carboxyl group ($\mathrm{COOH}$) can act as an acid by donating a proton.

Question 3

A researcher synthesizes a drug with a chiral carbon. Which of the following is most likely to be true regarding its biological activity?

Accepted Answer

The two enantiomers may have very different biological effects, with one possibly being therapeutic and the other harmful.

Question 4

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

Accepted Answer

Configuration refers to the fixed spatial arrangement of atoms that cannot be changed without breaking covalent bonds, while conformation refers to flexible arrangements that can change without breaking bonds.

Question 5

Which of the following is a correct application of the first law of thermodynamics to living cells?

Accepted Answer

Cells convert energy from nutrients or sunlight into work, heat, or the synthesis of complex biomolecules, but the total energy remains constant.

Question 6

A reaction has $\Delta H = -50\ \mathrm{kJ/mol}$ and $\Delta S = -0.1\ \mathrm{kJ/(mol\cdot K)}$. At what temperature (in Kelvin) does the reaction become non-spontaneous?

Accepted Answer

At $T > 500\ \mathrm{K}$, since $\Delta G = \Delta H - T\Delta S$ becomes positive.

Question 7

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

Accepted Answer

ATP acts as a universal energy currency, coupling exergonic and endergonic reactions.

Question 8

Which of the following statements about the four major classes of biomolecules is correct?

Accepted Answer

Proteins are linear polymers of amino acids, while lipids are aggregates of building blocks rather than true polymers.

Question 9

Which of the following scenarios best illustrates the concept of energy coupling in biological systems?

Accepted Answer

The hydrolysis of ATP ($\Delta G < 0$) is used to drive the synthesis of glucose-6-phosphate from glucose and phosphate ($\Delta G > 0$).

Question 10

Which of the following is a key difference between prokaryotic and eukaryotic cells?

Accepted Answer

Eukaryotic cells contain membrane-bound organelles, while prokaryotic cells do not.

Question 11

Which of the following best explains why the biological activity of stereoisomers can differ dramatically, as seen in the thalidomide case?

Accepted Answer

Biological molecules are stereospecific, so only one enantiomer may fit or interact properly with a biological target.

Question 12

Which of the following statements about the genetic basis of life is correct?

Accepted Answer

DNA stores genetic information, which is transcribed into RNA and then translated into protein, as described by the central dogma.

Question 13

A mutation changes a single nucleotide in a gene. Which of the following is a possible consequence according to the central dogma?

Accepted Answer

The amino acid sequence of the corresponding protein may change, potentially altering its structure and function.

Question 14

Which of the following best describes the second law of thermodynamics as it applies to living systems?

Accepted Answer

Living systems maintain order locally by increasing the entropy of their surroundings.

Question 15

Which of the following is an example of a geometric (cis-trans) isomer, and why is this distinction biologically important?

Accepted Answer

Unsaturated fatty acids can exist in cis or trans forms, which affects membrane fluidity and health.

Question 16

Which of the following best explains the advantage of constructing biomolecules as polymers from simple building blocks?

Accepted Answer

It allows for simplicity in synthesis and degradation, recycling of building blocks, and the generation of molecular diversity.

Question 17

Which of the following statements about in vitro and in vivo studies is correct?

Accepted Answer

In vitro studies allow for controlled experiments on isolated molecules, but may not reflect the complexity of living systems.

Question 18

Which of the following best illustrates the concept of the 'unity of biochemistry'?

Accepted Answer

All living organisms use a common set of building blocks and core biochemical processes, regardless of their size or complexity.

Module 1: Biochemistry and the Unity of Life – Foundations, Molecules, and Principles

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