5. A single polypeptide chain can have all of the following levels of structure EXCEPT:
(A) Primary structure
(B) Secondary structure
(C) Tertiary structure
(D) Quaternary structure

1. Which of the following describes the difference between two isotopes of the same element?(A) They have a different atomic number.(B) They have one more proton.(C) They have one more electron.(D) They have a different number of neutrons.

2. The property of water that allows hydrogen bonds to form between water molecules is primarily due to:(A) water's overall nonpolar nature.(B) the equal sharing of electrons between oxygen and hydrogen.(C) the polar covalent bonds between oxygen and hydrogen atoms.(D) water being a good solvent for hydrophobic substances.

3. If the pH of a solution decreases from 7 to 4, it means the concentration of hydrogen ions (H+) has:(A) decreased by a factor of 3. (B) decreased by a factor of 1000.(C) increased by a factor of 3. (D) increased by a factor of 1000.

4. Which of the following is defined as the study of carbon compounds?(A) Biochemistry (B) Organic chemistry(C) Physical chemistry (D) Inorganic chemistry

6. Which of the following is present in a prokaryotic cell?(A) Mitochondrion (B) Ribosome (C) Nuclear envelope (D) Chloroplast

7. For a resting neuron, which of the following is true regarding ion distribution and membrane potential?(A) The concentration of Na+ is higher inside the cell, and the membrane potential is positive.(B) The concentration of K+ is higher outside the cell, and the membrane potential is positive.(C) The concentration of Na+ is higher outside the cell, and the inside is negatively charged relative to the outside.(D) The concentration of K+ is higher outside the cell, and the inside is positively charged relative to the outside.

8. Which of the following classes of large biological molecules does NOT consist of polymers?(A) Carbohydrates (B) Proteins (C) Lipids (D) Nucleic acids

9. Which of the following processes involves the net movement of water across a selectively permeable membrane?(A) Active transport (B) Facilitated diffusion (C) Osmosis (D) Cotransport

10. To study the process of protein translation from mRNA, which cellular component would be most enriched in the finalpellet after cell fractionation?(A) Nuclei (B) Mitochondria(C) Pieces of plasma membranes (D) Ribosomes

11. Consider a metabolic pathway where compound X is converted to Y, and Y is converted to Z. If the enzyme converting X to Y is inhibited by the accumulation of Z, this is an example of:(A) Allosteric activation. (B) Competitive inhibition.(C) Noncompetitive inhibition. (D) Feedback inhibition.