Q: A solution has a pH of 4. What is the concentration of hydrogen ions $$[H^+] in $$this solution?

$$[H^+] = 1 \times 10$$^{-4}$$ \ \mathrm{M}$$

Question 1

Which of the following best describes why water has a high specific heat compared to other substances?

Accepted Answer

Because water molecules form extensive hydrogen bonds, which require more energy to break.

Question 2

A scientist discovers a new element with atomic number 12 and mass number 25. Which statement is correct about this element?

Accepted Answer

It has 12 protons, 13 neutrons, and 12 electrons.

Question 3

Which of the following best explains why saturated fats are solid at room temperature while unsaturated fats are liquid?

Accepted Answer

Saturated fats have only single bonds, allowing molecules to pack closely together.

Question 4

Which of the following is a correct comparison between peptide bonds and glycosidic linkages?

Accepted Answer

Peptide bonds join amino acids, while glycosidic linkages join monosaccharides.

Question 5

A solution has a pH of 4. What is the concentration of hydrogen ions $$[H^+] in $$this solution?

Accepted Answer

$$[H^+] = 1 	imes 10$$^{-4}$$ \ \mathrm{M}$$

Question 6

Which of the following statements about the secondary structure of proteins is correct?

Accepted Answer

It includes alpha helices and beta sheets stabilized by hydrogen bonds between backbone atoms.

Question 7

Which of the following best describes the difference between polar covalent bonds and ionic bonds?

Accepted Answer

Polar covalent bonds involve partial charges due to unequal sharing of electrons, while ionic bonds involve full charges due to electron transfer.

Question 8

A cell is placed in a solution and water moves into the cell, causing it to swell. Which term best describes the solution relative to the cell?

Accepted Answer

Hypotonic

Question 9

Which of the following is a direct consequence of the antiparallel arrangement of DNA strands in the double helix?

Accepted Answer

Complementary base pairing occurs with hydrogen bonds between bases.

Question 10

Which of the following best explains why carbon atoms can form such a wide variety of organic molecules?

Accepted Answer

Carbon can form up to four covalent bonds with other atoms.

Question 11

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

Accepted Answer

ATP stores energy in its phosphate bonds, which is released during hydrolysis and used to drive endergonic reactions.

Question 12

A mutation causes a single amino acid change in the primary structure of a protein. Which of the following is most accurate?

Accepted Answer

Some single amino acid changes can have dramatic effects, as in sickle-cell hemoglobin, but not all will.

Question 13

Which of the following best describes the difference between facilitated diffusion and active transport across a cell membrane?

Accepted Answer

Facilitated diffusion moves substances down their concentration gradient without energy input; active transport moves substances against their gradient using energy.

Question 14

Which of the following is a correct statement about the relationship between enthalpy ($$\Delta H$$), entropy ($$\Delta S$$), and Gibbs free energy ($$\Delta G) in $$biological reactions?

Accepted Answer

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

Question 15

Which of the following is NOT a function of carbohydrates in cells?

Accepted Answer

Catalyzing chemical reactions

Question 16

Which of the following best explains why phospholipids spontaneously form bilayers in water?

Accepted Answer

Their amphipathic nature causes hydrophobic tails to avoid water and hydrophilic heads to interact with water.

Question 17

Which of the following statements about the RNA world hypothesis is correct?

Accepted Answer

It proposes that RNA was the first genetic material and could both store information and catalyze reactions.

Question 18

Which of the following best describes the effect of increasing temperature on enzyme-catalyzed reactions in cells?

Accepted Answer

Increasing temperature increases enzyme activity up to an optimal point, after which the enzyme denatures and activity decreases.

Question 19

Which of the following is a correct statement about the permeability of lipid bilayers?

Accepted Answer

Small, nonpolar molecules cross lipid bilayers more easily than large, charged molecules.

Question 20

Which of the following best describes the process of hydrolysis in biological polymers?

Accepted Answer

It breaks polymers into monomers by adding a water molecule.

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