Question 1

Which of the following statements best explains why carbon is the backbone of most biological molecules?

Accepted Answer

Carbon can form up to four covalent bonds, allowing for complex and diverse molecular structures.

Question 2

Which of the following best describes a compound?

Accepted Answer

A substance consisting of two or more chemically bound elements in a fixed ratio.

Question 3

Why are hydrogen, carbon, nitrogen, and oxygen the most abundant elements in living organisms?

Accepted Answer

They form strong covalent bonds and are able to create stable, diverse molecules essential for life.

Question 4

Which of the following is true about covalent bonds in biological molecules?

Accepted Answer

Covalent bonds involve the sharing of electron pairs between atoms.

Question 5

A molecule of water ($$H_2O) is $$held together by which type of bond between the hydrogen and oxygen atoms?

Accepted Answer

Polar covalent bonds

Question 6

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

Accepted Answer

Polar covalent bonds involve unequal sharing of electrons, while nonpolar covalent bonds involve equal sharing.

Question 7

Which of the following statements about hydrogen bonds is correct?

Accepted Answer

Hydrogen bonds are weak interactions that occur between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom.

Question 8

Which of the following best explains why sodium chloride ($$NaCl) $$forms an ionic bond?

Accepted Answer

Sodium donates an electron to chlorine, resulting in oppositely charged ions that attract each other.

Question 9

Which of the following is a real-life example of the importance of hydrogen bonds in biology?

Accepted Answer

Hydrogen bonds hold together the two strands of DNA in the double helix.

Question 10

Which of the following best describes the relationship between atomic number and the identity of an element?

Accepted Answer

The atomic number is the number of protons in the nucleus, which defines the element.

Question 11

A neutral atom of nitrogen has an atomic number of 7. How many electrons does it have?

Accepted Answer

7

Question 12

Which of the following statements about the distribution of elements in the Earth's crust versus the human body is correct?

Accepted Answer

Elements like carbon, hydrogen, nitrogen, and oxygen are much more abundant in the human body than in the Earth's crust.

Question 13

Which of the following best explains why atoms with unpaired valence electrons are chemically reactive?

Accepted Answer

They tend to form bonds with other atoms to fill their valence shells and achieve stability.

Question 14

Which of the following is NOT a type of chemical bond important in biological molecules?

Accepted Answer

Metallic bonds

Question 15

A molecule of methane ($$CH_4) is an $$example of which type of covalent bond?

Accepted Answer

Nonpolar covalent bond

Question 16

Which of the following best describes the role of functional groups in organic molecules?

Accepted Answer

Functional groups confer specific chemical properties and reactivity to organic molecules.

Question 17

Which of the following scenarios best illustrates the concept of chemical reactivity in atoms?

Accepted Answer

A sodium atom donates an electron to a chlorine atom, resulting in the formation of $$Na^+$$ and $$Cl^-$$ ions.

Question 18

Which of the following best explains why water is a good solvent for many biological molecules?

Accepted Answer

Water's polarity allows it to form hydrogen bonds with many different molecules.

Question 19

Which of the following is a correct statement about the relationship between molecules and compounds?

Accepted Answer

All compounds are molecules, but not all molecules are compounds.

Question 20

Which of the following best describes the role of electrons in chemical bonding?

Accepted Answer

Electrons in the valence shell are involved in forming chemical bonds to achieve stable electron configurations.

Chemical Composition of Cells: Atoms, Bonds, and Organic Molecules

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