Chapter 2 - The Molecules of Life

Question 0

What is the structure of an atom?

Answer 0

An atom is made up of neutrons, protons, and electrons. The neutrons and protons form a nucleus.

Question 1

Distinguish between an element and a compound.

Answer 1

An element is a pure substance that cannot be broken down further.
A compound is a substance formed when two or more elements mare chemically bonded together.

Question 2

What are the six elements that make up 96-98% of living matter?

Answer 2

Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, and Sulfur.

Question 3

Define trace element and give examples.

Answer 3

Trace elements are elements that an organism needs very small quantities of to survive. Examples are zinc, manganese, and iodine.

Question 4

What are the bonds formed within molecules?

Answer 4

Covalent bonds and ionic bonds.

Question 5

What are the bonds formed between molecules?

Answer 5

Hydrogen bonds, hydrophobic interactions, and van der Waals interactions.

Question 6

What is a covalent bond?

Answer 6

A covalent bond is a chemical bond formed by a shared pair of electrons holding two different atoms together.

Question 7

What is a polar covalent bond?

Answer 7

A polar covalent bond is a chemical bond formed by unequal sharing of electrons between two atoms.

Question 8

What is an ionic bond?

Answer 8

An ionic bond is the bonding of two atoms resulting from the attraction of opposite charges.

Question 9

Explain why strong covalent bonds and weak bonds are essential in living organisms.

Answer 9

Covalent bonds link atoms to form a cell’s molecules while weak bonds can be broken down and put together easily. An example is DNA: the phosphodiester bonds form the backbones of the strands and the hydrogen bonds hold the two strands together. However, the hydrogen bonds can be unzipped easily for duplication.

Question 10

What is a hydrogen bond?

Answer 10

A hydrogen bond is when a hydrogen atom covalently bound to an electronegative atom interacts with an electronegative atom of another molecule. An example is hydrogen bonding in water.

Question 11

What is a hydrophobic interaction?

Answer 11

A hydrophobic interaction is an interaction of nonpolar substances and polar substances. An example is oil and water.

Question 12

What is a van der Waals interaction?

Answer 12

A van der Waals interaction is the interaction of electrons of nonpolar substances.

Question 13

Give an example that illustrates how a molecule’s shape can determine its biological function.

Answer 13

A phospholipid is made up of a phosphate head and a fatty acid tail. The phosphate head is hydrophillic while the fatty acid tail is hydrophobic. The phospholipid bilayer makes up the cell membrane and helps to control what goes in and out of a cell. Another example is DNA.

Question 14

Why are water molecules (a) polar and (b) capable of hydrogen bonds?

Answer 14

Water molecules are formed by a covalent bond. Oxygen is much larger than hydrogen, so the electrons are more attracted to them. This results in a positive charge on the oxygen end and a negative charge on the hydrogen end, making the molecule polar. This is also why water molecules are capable of hydrogen bonds since hydrogen is positively charged.

Question 15

List 5 properties of water that are emergent properties resulting from hydrogen bonding.

Answer 15

1. Cohesion and adhesion
2. Moderation of temperature
3. Insulation
4. Excellent solvent
5. Weak acid

Question 16

Distinguish among a solute, a solvent, and a solution.

Answer 16

A solute is the dissolved substance in a solution.
A solvent is the major component in a solution.
A solution is a homogeneous mixture containing particles the size of a typical ion or covalent molecule.

Question 17

Distinguish between hydrophobic and hydrophilic substances.

Answer 17

A hydrophobic substance is a nonpolar substance that is insoluble in water and is “water fearing” or “water repelling”. A hydrophilic substance is “water loving” and is soluble in water (can be dissolved into ions).

Question 18

Define acid, base, and pH.

Answer 18

An acid is a substance that provides H+ ions in water.
A base is a substance that provides OH- ions in water.
pH is the concentration of H+ ions in water.
–> pH = -log[H+], where [H+] is the concentration of protons

Question 19

Explain how carbon’s electron configuration accounts for its ability to form large, complex, and diverse organic molecules.

Answer 19

Carbon has four valence electrons, which allow the formation of 4 covalent bonds with a variety of atoms to stabilize it. This versatility leads to the diversity of organic molecules.

Question 20

Name the major functional groups found in organic molecules.

Answer 20

1. Hydroxyl group (OH)
2. Carbonyl group (CO)
3. Carboxyl group (COOH)
4. Amino group (NH2)
5. Sulfhydryl group (SH)
6. Phosphate group (OPO3)2-
7. Methyl group (CH3)

Question 21

List the four major classes of macromolecules.

Answer 21

Proteins, nucleic acids, carbohydrates, and lipids.

Question 22

Identify the monomers for proteins, nucleic acids, and carbohydrates.

Answer 22

Proteins – amino acids
Nucleic acids – nucleotides
Carbohydrates – monosaccharides

Question 23

Why are lipids not considered true polymers like the other macromolecules?

Answer 23

Their monomer units, fatty acids, are not linked by covalent bonds.

Question 24

Define adhesion.

Answer 24

Adhesion is the ability to stick to something.

Question 25

Define cohesion.

Answer 25

Cohesion is the ability to stick together.

Question 26

What is an anion?

Answer 26

An anion is a negatively charged ion.

Question 27

What is a cation?

Answer 27

A cation is a positively charged ion.