Question 1

Which of the following statements best explains why water is considered essential for life at the cellular level?

Accepted Answer

Water acts as a universal solvent, allowing most biochemical reactions to occur in aqueous environments.

Question 2

A solution contains 180 g of glucose (molecular weight = 180) dissolved in 1 liter of water. What is the molarity of this solution?

Accepted Answer

$$1\ 	ext{M}$$

Question 3

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

Accepted Answer

Covalent bonds involve the sharing of electrons, while ionic bonds involve the transfer of electrons.

Question 4

Why are carbon–carbon double bonds more rigid than single bonds?

Accepted Answer

Double bonds are shorter and prevent rotation around the bond axis.

Question 5

A chemist wants to prepare 0.5 M NaCl solution. The molecular weight of NaCl is 58 g/mol. How many grams of NaCl are needed to make 1 liter of this solution?

Accepted Answer

$$29\ 	ext{g}$$

Question 6

Which property of water is primarily responsible for its ability to dissolve ionic compounds like NaCl?

Accepted Answer

Its ability to form hydrogen bonds with ions

Question 7

Which of the following best describes Avogadro’s number?

Accepted Answer

The number of molecules in one mole of a substance

Question 8

Which of the following scenarios best illustrates the formation of a hydrogen bond?

Accepted Answer

A hydrogen atom covalently bonded to oxygen in one water molecule is attracted to the oxygen atom of a neighboring water molecule.

Question 9

Which statement about electron shells is correct?

Accepted Answer

Atoms are most stable when their outermost electron shell is completely filled.

Question 10

A protein binds to another protein in a cell through complementary charges. Which type of interaction is primarily responsible for this binding?

Accepted Answer

Noncovalent interactions such as hydrogen bonds and electrostatic attractions

Question 11

Which of the following molecules would be considered hydrophobic?

Accepted Answer

A molecule with many C-H bonds and few or no polar groups

Question 12

Which of the following best explains why salts like NaCl dissolve readily in water?

Accepted Answer

Water molecules surround and stabilize the ions through charge interactions.

Question 13

Which of the following is true about the atomic nucleus?

Accepted Answer

It contains protons and neutrons and is much smaller than the electron cloud.

Question 14

Which of the following is a consequence of the polarity of water molecules?

Accepted Answer

Water molecules can form hydrogen bonds with each other.

Question 15

A molecule of ethene (C$$_2H$_4) $$contains a double bond between the two carbon atoms. Which property does this double bond confer to the molecule?

Accepted Answer

It restricts rotation and makes the molecule more rigid.

Question 16

Which of the following best describes a mole in chemistry?

Accepted Answer

The amount of substance containing $$6 	imes 10$$^{23}$$ particles.

Question 17

Which of the following is a real-world example of a polar covalent bond?

Accepted Answer

The O-H bond in a water molecule

Question 18

Why are noncovalent bonds important in biological systems, even though they are weaker than covalent bonds?

Accepted Answer

They allow for transient interactions necessary for dynamic cellular processes.

Question 19

Which of the following best explains why noble gases like neon are chemically unreactive?

Accepted Answer

Their outermost electron shells are completely filled.

Question 20

A scientist observes that a protein binds to another protein only in the presence of water. Which property of water most likely facilitates this interaction?

Accepted Answer

Water forms hydrogen bonds that stabilize the interaction between the proteins.

Introduction to Biochemistry: Key Concepts for Biology

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