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 statements best explains why water is an excellent solvent for ionic compounds?

Accepted Answer

Water is a polar molecule, allowing it to form hydration shells around ions through hydrogen bonding and electrostatic interactions.

Question 2

A scientist discovers a new organism with cells that lack a nucleus, have circular DNA, and possess unique membrane lipids not found in bacteria or eukaryotes. To which domain does this organism most likely belong?

Accepted Answer

Archaea

Question 3

Which of the following best describes the relationship between the structure and function of proteins?

Accepted Answer

The primary structure of a protein determines its 3D shape, which in turn determines its function.

Question 4

Which of the following functional groups is both hydrophilic and commonly found in nucleic acids?

Accepted Answer

Phosphate group

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 best distinguishes a saturated fatty acid from an unsaturated fatty acid?

Accepted Answer

Saturated fatty acids contain only single bonds between carbon atoms, while unsaturated fatty acids contain one or more double bonds.

Question 7

Which of the following is a correct statement about the endosymbiotic theory?

Accepted Answer

It proposes that mitochondria and chloroplasts originated from free-living prokaryotes engulfed by ancestral eukaryotic cells.

Question 8

Which of the following best describes the difference between DNA and RNA?

Accepted Answer

DNA contains deoxyribose and thymine, while RNA contains ribose and uracil.

Question 9

A molecule with the formula $$C_{6}H$$_{12}$$O_{6}$ is classified as which type of macromolecule, and what is its primary function in cells?

Accepted Answer

Carbohydrate; energy storage and fuel

Question 10

Which of the following best explains why phospholipids form bilayers in aqueous environments?

Accepted Answer

Their hydrophilic heads interact with water while their hydrophobic tails avoid water, resulting in a bilayer arrangement.

Question 11

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

Accepted Answer

Long-term energy storage

Question 12

A buffer solution is added to a beaker of pure water. Which of the following best describes the buffer's role if a strong acid is then added?

Accepted Answer

The buffer will absorb excess $$H^+$$ ions, minimizing the change in pH.

Question 13

Which of the following best describes the difference between structural isomers and enantiomers?

Accepted Answer

Structural isomers differ in the covalent arrangement of their atoms, while enantiomers are mirror images of each other.

Question 14

Which of the following best explains why cellulose is not digestible by humans, while starch is?

Accepted Answer

Cellulose has $$\beta-1$$,4-glycosidic linkages, which human digestive enzymes cannot hydrolyze, while starch has $$\alpha-1$$,4-glycosidic linkages, which can be broken down.

Question 15

Which of the following best describes the role of ribosomes in the cell?

Accepted Answer

They are the sites of protein synthesis, translating mRNA into polypeptides.

Question 16

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

Accepted Answer

Hypotonic

Question 17

Which of the following statements about the cytoskeleton is correct?

Accepted Answer

It provides structural support, enables cell movement, and facilitates intracellular transport.

Question 18

Which of the following best describes the process of dehydration synthesis?

Accepted Answer

It joins monomers by removing a molecule of water, forming a covalent bond.

Question 19

Which of the following is a correct statement about the plasma membrane?

Accepted Answer

It is composed of a phospholipid bilayer with embedded proteins, providing selective permeability.

Question 20

Which of the following best explains why ATP is considered a nucleotide?

Accepted Answer

It consists of a ribose sugar, adenine base, and three phosphate groups.

BIOL 251 Exam 1 Study Guide: Organization of Life, Chemical Context, and Cells

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