Question 1

Which of the following best explains why DNA is more stable than RNA in cellular environments?

Accepted Answer

DNA has a deoxyribose sugar lacking a hydroxyl group at the 2' carbon, reducing its reactivity.

Question 2

A DNA template strand has the sequence 3'–C T A G G C–5'. What is the sequence and orientation of the RNA transcript produced from this template?

Accepted Answer

5'–G A U C C G–3'

Question 3

Which of the following changes would most likely decrease the amount of RNA produced from a gene in a eukaryotic cell?

Accepted Answer

A mutation that disrupts the binding site for general transcription factors in the promoter.

Question 4

Which of the following best describes the difference between competitive inhibition and allosteric regulation of an enzyme?

Accepted Answer

Competitive inhibitors bind to the active site, while allosteric regulators bind elsewhere and change the enzyme's shape.

Question 5

A cell is building a large RNA molecule from nucleotides. Which of the following statements about the energy changes in this process is correct?

Accepted Answer

The process is anabolic and requires an input of energy, often coupled to ATP hydrolysis.

Question 6

Which of the following best explains why enzymes increase the rate of chemical reactions?

Accepted Answer

Enzymes lower the activation energy ($$E_a) $$required for the reaction, but do not change the overall $$\Delta G.$$

Question 7

Which of the following is a correct pairing between a codon on mRNA and its corresponding anticodon on tRNA during translation?

Accepted Answer

mRNA codon 5'–GAC–3'; tRNA anticodon 3'–CUG–5'

Question 8

Which of the following best describes the role of the 5' cap and 3' poly-A tail added to eukaryotic mRNA?

Accepted Answer

They are required for the mRNA to be exported from the nucleus and protect it from degradation.

Question 9

Which of the following statements about the four levels of protein structure is correct?

Accepted Answer

Tertiary structure refers to the overall 3D shape of a single polypeptide, stabilized by interactions among R groups.

Question 10

A metabolic pathway produces a product that, when abundant, binds to an enzyme early in the pathway and decreases its activity. What is this an example of?

Accepted Answer

Feedback inhibition

Question 11

Which of the following best describes the difference between DNA replication and transcription?

Accepted Answer

Replication copies the entire DNA molecule, while transcription copies only a gene into RNA.

Question 12

Which of the following statements about ATP is correct?

Accepted Answer

ATP hydrolysis releases energy that can be used to drive endergonic cellular reactions.

Question 13

Which of the following scenarios illustrates the coupling of an exergonic and an endergonic reaction in a cell?

Accepted Answer

ATP hydrolysis ($$\Delta G  0).$$

Question 14

Which of the following best explains why hydrophobic amino acid side chains are typically found in the interior of soluble proteins?

Accepted Answer

Hydrophobic side chains avoid contact with water, so they are buried inside the protein during folding.

Question 15

Which of the following is true regarding the flow of genetic information in a eukaryotic cell?

Accepted Answer

DNA is transcribed into pre-mRNA, which is processed into mature mRNA, exported to the cytoplasm, and translated into protein.

Question 16

Which of the following best describes the role of the promoter in gene expression?

Accepted Answer

It is a DNA sequence where RNA polymerase and transcription factors bind to initiate transcription.

Question 17

Which of the following statements about the first and second laws of thermodynamics as applied to cells is correct?

Accepted Answer

Cells transform energy but cannot create or destroy it (first law), and some energy is always lost as heat, increasing entropy (second law).

Question 18

Which of the following is a correct description of the difference between an amino acid's shared and variable components?

Accepted Answer

All amino acids share an amino group, a carboxyl group, and a central carbon, but each has a unique R group (side chain).

Unit 2 Study Guide: Nucleic Acids, Proteins, and Metabolism

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