Question 1

Which of the following best describes the relationship between atoms, molecules, and compounds in living organisms?

Accepted Answer

Atoms combine to form molecules, and molecules combine to form compounds that are essential for life.

Question 2

Which four elements make up approximately 96% of living matter?

Accepted Answer

Oxygen, carbon, hydrogen, and nitrogen

Question 3

A radioactive isotope is useful in biological research because:

Accepted Answer

It can be used as a tracer to follow the movement of substances within organisms.

Question 4

The atomic number of an element is defined as:

Accepted Answer

The number of protons in the nucleus of an atom

Question 5

Which of the following equations correctly represents the formation of sodium chloride from its elements?

Accepted Answer

$$\mathrm{Na} + \mathrm{Cl} \rightarrow \mathrm{NaCl}$$

Question 6

Which statement best explains why water is a polar molecule?

Accepted Answer

Oxygen is more electronegative than hydrogen, causing unequal sharing of electrons.

Question 7

If an atom has 6 protons, 6 neutrons, and 6 electrons, what is its atomic mass?

Accepted Answer

$$6 + 6 = 12$$

Question 8

Which of the following best describes an ionic bond?

Accepted Answer

A bond formed by the attraction between oppositely charged ions

Question 9

Which of the following is a real-world application of radioactive isotopes in biology?

Accepted Answer

Using carbon-14 to date ancient fossils

Question 10

A molecule of methane ($$\mathrm{CH}_4) is $$formed when:

Accepted Answer

One carbon atom forms four single covalent bonds with four hydrogen atoms

Question 11

Which of the following best explains why sodium (Na) and chlorine (Cl) form an ionic bond?

Accepted Answer

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

Question 12

Which of the following is NOT a correct pairing of biological organization level and its example?

Accepted Answer

Molecules – a population of deer

Question 13

Which property of an atom determines how it will interact with other atoms?

Accepted Answer

The number of electrons in its outermost shell

Question 14

Which of the following best describes a covalent bond?

Accepted Answer

A bond where two atoms share one or more pairs of electrons

Question 15

Which of the following statements about hydrogen bonds is correct?

Accepted Answer

They are weak attractions between a hydrogen atom and an electronegative atom like oxygen or nitrogen.

Question 16

A scientist is studying a molecule that has a region with a partial positive charge and a region with a partial negative charge. This molecule is most likely:

Accepted Answer

Polar

Question 17

Which of the following best explains why trace elements are important for living organisms?

Accepted Answer

They are required in small amounts for essential biological processes.

Question 18

Which of the following scenarios best illustrates the concept of emergent properties in biology?

Accepted Answer

A functioning heart can pump blood, but individual heart cells cannot.

Question 19

If a neutral atom of chlorine has 17 protons and 18 neutrons, what is its mass number?

Accepted Answer

$$17 + 18 = 35$$

Question 20

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.

AP/DE Biology Chapter 2

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