Chapter 2: The Chemistry of Biology

Question 1

__________ is the smallest chemical unit of a type of pure substance.

1. An atom
2. A proton
3. A molecule
4. An amino acid

Answer 1

an atom

Question 2

Which of the following is NOT a property of water?

1. It is less dense when frozen than when it’s a liquid.
2. It is a solvent for both polar and nonpolar molecules dissolve in it.
3. It takes a lot of energy to raise the temperature of water.
4. Water molecules stick to each other.
5. A lot of energy must be withdrawn from water in order to lower its temperature.

Answer 2

It is a solvent for both polar and nonpolar molecules dissolve in it

Question 3

The tendency of molecules to stick together, called cohesion, is stronger in water than in other liquids because:

1. the polarity of water allows an oxygen atom from one water molecule to form a hydrogen bond with the oxygen atom of another water molecule.
2. the polarity of water allows a hydrogen atom from one water molecule to form a hydrogen bond with the oxygen atom of another water molecule.
3. the polarity of water allows a hydrogen atom from one water molecule to form an ionic bond with the oxygen atom of another water molecule.
4. the polarity of water allows a hydrogen atom from one water molecule to form a hydrogen bond with the hydrogen atom of another water molecule.
5. the polarity of water allows a hydrogen atom from one water molecule to form a covalent bond with the oxygen atom of another water molecule.

Answer 3

the polarity of water allows a hydrogen atom from one water molecule to form a hydrogen bond with the oxygen atom of another water molecule.

Question 4

What type of bond is illustrated by the dotted lines between the water molecules diagrammed below?
XXXXX

1. ionic bond
2. hydrogen bond
3. covalent bond
4. peptide bond

Answer 4

hydrogen bond

Question 5

Water consists of polar molecules. Due to this property, what types of substances can water very effectively dissolve?

1. polar substances
2. non-polar substances
3. lipids
4. all organic molecules

Answer 5

polar substances

Question 6

The nucleus of an atom is usually made up of:

1. neutrinos, which have no electrical charge.
2. protons, which a positive charge, and neutrons, which have no electrical charge.
3. protons, neutrons, and proteins that hold them together.
4. neutrons, which have no electrical charge.
5. protons, which have a positive electrical charge, and proteins, which hold them together.

Answer 6

protons, which a positive charge, and neutrons, which have no electrical charge

Question 7

Relative to protons:

1. electrons have approximately the same mass.
2. electrons have a significantly stronger positive charge.
3. electrons have significantly greater mass.
4. electrons have significantly less mass.
5. None of the above; electrons have no mass.

Answer 7

electrons have significantly less mass

Question 8

In the diagram of an atom below, what structure represents an electron?
XXXX
A
B
C
D

Answer 8

C

Question 9

How many hydrogen bonds are explicitly represented in this figure?
XXXXX

1. 1
2. 0
3. 4
4. 8
5. 10

Answer 9

4

Question 10

Which of the following molecules is NOT formed by covalent bonding?

1. NaCl
2. H2
3. H2O
4. CH4
5. O2

Answer 10

NaCl

Question 11

Why do coastal areas have milder, less variable climates than inland areas?

1. Because water is a good solvent, it is able to dissolve the photons in light, reducing their ability to heat or cool the land.
2. Large bodies of water have high salt concentrations and salt absorbs a large proportion of the light energy that would have warmed the land.
3. Coastal areas are concentrated near the equator, which varies less than other parts of the globe in the angle at which the sun’s light hits it.
4. Large bodies of water, especially oceans, can absorb huge amounts of heat from the sun during warm times of the year, reducing temperature increases on the land. Similarly, during cold times of year the ocean slowly cools, giving off heat that reduces the temperature drop on shore.
5. None of the above. No one knows why coastal areas have milder, less variable climates than inland areas.

Answer 11

Large bodies of water, especially oceans, can absorb huge amounts of heat from the sun during warm times of the year, reducing temperature increases on the land. Similarly, during cold times of year the ocean slowly cools, giving off heat that reduces the temperature drop on shore

Question 12

All matter on earth, both living and non-living, is made up of:

1. carbohydrates.
2. atoms.
3. DNA.
4. cells.
5. phospholipids.

Answer 12

atoms

Question 13

The number of electrons in the outermost shell of a sodium atom (Na) is 1. Chlorine (Cl) has 7 electrons in its outermost shell. A molecule of common table salt is NaCl. Based on the number of electrons in the outermost shell of each element, what type of chemical bond exists between the two atoms of an NaCl molecule?

1. hydrogen bond
2. peptide bond
3. covalent bond
4. ionic bond

Answer 13

ionic bond

Question 14

Consider the following chemical reaction:

6CO2 + 6H2O → C6H12O6 + 6O2

Which of the following correctly names the reactant(s)?
1. CO2
2. C6H12O6 and O2
3. CO2 and H2O
4. C6H12O6

Answer 14

CO2 and H2O

Question 15

An atom of iron has the atomic number 26. This means that:

1. it has an atomic mass of 26.
2. it has 26 protons.
3. it has 13 electrons.
4. it has 13 neutrons.
5. it has 52 protons.

Answer 15

it has 26 protons

Question 16

Which four chemical elements make up around 96% of the biomass in plants, animals, fungi, and bacteria?

1. carbon, oxygen, hydrogen, meanorium
2. carbon, oxygen, hydrogen, nitrogen
3. carbon, oxygen, hydrogen, potassium
4. carbon, oxygen, hydrogen, uranium
5. carbon, oxygen, hydrogen, sulfur

Answer 16

carbon, oxygen, hydrogen, and nitrogen

Question 17

The four most abundant elements in living organisms are:

1. sodium, nitrogen, carbon, and silicon.
2. carbon, nitrogen, oxygen, and calcium.
3. carbon, hydrogen, nitrogen, and phosphorus.
4. carbon, nitrogen, potassium, and oxygen.
5. hydrogen, nitrogen, oxygen, and carbon.

Answer 17

hydrogen, nitrogen, oxygen, and carbon

Question 18

One important difference between covalent and ionic bonds is that:

1. in covalent bonds two atoms share electrons while in ionic bonds two atoms of opposite charge are attracted to each other.
2. ionic bonds only occur among water-soluble elements.
3. in ionic bonds two atoms share electrons, while in covalent bonds one atom gives one or more electrons to the other atom.
4. in ionic bonds both protons and electrons can be shared while in covalent bonds only electrons can be shared.
5. ionic bonds are much stronger than covalent bonds.

Answer 18

in covalent bonds two atoms share electrons while in ionic bonds two atoms of opposite charge are attracted to each other

Question 19

Look at the carbon atom diagrammed below and the accompanying legend. Why does the carbon atom have no overall (or net) electrical charge? XXXX

1. the number of neutrons equals the number of protons
2. the number of electrons equals the number of neutrons
3. the number of electrons equals the number of protons
4. there are only two electrons in the outermost shell

Answer 19

the number of electrons equals the number of protons

Question 20

If an atom has 7 protons and 7 electrons, what is the atomic number of the atom?

1. 7
2. 14
3. 49
4. cannot be determined from the information given

Answer 20

7