Question 1

Which of the following best describes the Miller-Urey experiment and its significance in the study of the origins of life?

Accepted Answer

It demonstrated that simple organic molecules could be synthesized from inorganic precursors under conditions simulating the early Earth's atmosphere.

Question 2

Which of the following functional groups is commonly found in amino acids and is responsible for their zwitterionic nature at physiological pH?

Accepted Answer

Amino ($$-\mathrm{NH}_2) $$and carboxyl ($$-\mathrm{COOH}) $$groups

Question 3

Which of the following statements about hydrogen bonding in water is CORRECT?

Accepted Answer

Each water molecule can form up to four hydrogen bonds, leading to a high boiling point relative to its molecular weight.

Question 4

A solution has $$[\mathrm{H}^+] = 1 	imes 10$$^{-5}$$\ \mathrm{M}. $$What is the pH of this solution?

Accepted Answer

$$5$$

Question 5

Which of the following best explains the hydrophobic effect in biological systems?

Accepted Answer

Nonpolar molecules aggregate in aqueous solution to minimize disruption of hydrogen-bonded water networks, increasing entropy of the system.

Question 6

Which of the following is TRUE regarding the structure of DNA as described by Watson and Crick?

Accepted Answer

The two strands are antiparallel and held together by hydrogen bonds between complementary bases.

Question 7

Which enzyme is responsible for unwinding the DNA double helix during replication?

Accepted Answer

Helicase

Question 8

Given a weak acid with $$K_a = 1.0 	imes 10$$^{-5}$$, what is its pK_a$?

Accepted Answer

$$5$$

Question 9

Which of the following best describes the function of a buffer in biological systems?

Accepted Answer

A buffer resists changes in pH upon addition of small amounts of acid or base.

Question 10

Which of the following statements about amino acid stereochemistry is CORRECT?

Accepted Answer

Most naturally occurring amino acids in proteins are L-isomers.

Question 11

A peptide has the sequence Ala-Glu-Lys. Given the following $$pK_a$$ values: $$\alpha-$$COOH = $$2.0$$, $$\alpha-NH$_2$$ = $$9.0$$, Glu side chain = $$4.1$$, Lys side chain = $$10.5. $$What is the net charge of the peptide at pH $$7.0$$?

Accepted Answer

$$-1$$

Question 12

Which of the following best describes the specificity of trypsin in protein sequencing?

Accepted Answer

Trypsin cleaves peptide bonds on the carboxyl side of lysine and arginine residues.

Question 13

Which of the following statements about the Ramachandran diagram is TRUE?

Accepted Answer

It shows the allowed values of phi ($$\phi) $$and psi ($$\psi) $$angles for amino acid residues in a polypeptide chain.

Question 14

Which of the following amino acids is most likely to be found on the interior of a globular protein?

Accepted Answer

Leucine

Question 15

A protein domain typically consists of how many amino acid residues?

Accepted Answer

100–200

Question 16

Which of the following best describes the Central Dogma of Molecular Biology?

Accepted Answer

DNA is transcribed into RNA, which is then translated into protein.

Question 17

Which of the following is a key feature that distinguishes prokaryotic cells from eukaryotic cells?

Accepted Answer

Prokaryotic cells lack membrane-bound organelles such as a nucleus.

Question 18

Which of the following statements about the carbonic acid-bicarbonate buffer system in blood is CORRECT?

Accepted Answer

It helps maintain blood pH by neutralizing small amounts of added acid or base.

Question 19

Which of the following best describes the formation of a peptide bond?

Accepted Answer

A condensation reaction between the carboxyl group of one amino acid and the amino group of another, releasing water.

Principles of Biochemistry: Exam 1 Study Guide (Chapters 1, 2, 4, 5, 6)

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