Chapter 2

Question 1

Element

Answer 1

A substance that is composed of a single type of atom and cannot be separated into simpler parts by chemical methods; 92 are naturally occurring

Question 2

4 Most Common Elements Found in Organisms

Answer 2

• Carbon (C)
• Hydrogen (H)
• Oxygen (O)
• Nitrogen (N)

Question 3

Atoms

Answer 3

The basic units of all matter; composed of three subatomic particles:

• Neutrons
• Protons
• Electrons

Question 4

Neutrons

Answer 4

Uncharged particles found in the nucleus of an atom

Question 5

Protons

Answer 5

Positively charged particles found in the nucleus of an atom

Question 6

Electrons

Answer 6

Negatively charged particles that form a “cloud” around the nucleus of an atom

Question 7

Atomic Number

Answer 7

The number of protons in the nucleus of an atom (same number of electrons)

Question 8

Atomic Weight

Answer 8

The sum of the number of protons and neutrons in an atom

Question 9

Isotope

Answer 9

Forms of the same chemical element that differ in their number of neutrons; useful tools in biological research

Question 10

Molecule

Answer 10

Two or more atoms held together by chemical bonds

Question 11

Compound

Answer 11

A molecule consisting of more than one element

Question 12

Chemical Bond

Answer 12

Form between the outer (valence) shell of atoms when electrons are lost, gained or shared in order to achieve their most stable state

Question 13

Ionic Bonds

Answer 13

Form between cations and anions because of strong attractions between positive and negative charges

Question 14

Cation

Answer 14

Negatively charged ion; gains electrons

Question 15

Anion

Answer 15

Positively charged ion; losses electrons

Question 16

Ion

Answer 16

An atom that is no longer neutral due to the loss or gain of an electron

Question 17

Covalent Bond

Answer 17

Strong chemical bond formed by the sharing of electrons between atoms (pairs of valence electrons)

Question 18

Valence Electrons

Answer 18

Found in an atom’s outer shell

Question 19

Non-Polar Covalent Bond

Answer 19

The electrons are shared equally

Question 20

Polar Covalent Bond

Answer 20

The electrons are shared unequally

Question 21

Hydrogen Bond

Answer 21

Weak bond formed when a hydrogen atom in a polar molecule is attracted to an electronegative atom in the same or another polar molecule

Question 22

pH

Answer 22

A measure of acidity of aqueous solutions:

• 0-6: acidic
• 7: neutral
• 8-14: basic (alkaline)

Question 23

Buffer

Answer 23

A compound that stabilizes the pH of a solution; prevents a dramatic rise or fall in pH

Question 24

Macromolecules

Answer 24

Large molecules that contain 10S of atoms to billions of atoms; complex enough that life is usually necessary to make them
- organic: contain at least carbon and hydrogen

Question 25

4 Types of Macromolecules

Answer 25

- Carbohydrates - Lipids - Proteins - Nucleic Acids

Question 26

Carbohydrates

Answer 26

Include sugars, starch, glycogen, chitin, cellulose, peptidoglycan; most are composed of ringed molecules (one up to thousands)

Question 27

Monosaccharides

Answer 27

Simple sugars; primary choice to make cellular energy (ATP)

Question 28

Polysaccharides

Answer 28

Carbohydrates that cells make to store energy in the form of a carbohydrate ( glycogen in animals, starch in plants); Complex carbohydrate molecules that cells use as building blocks of cell walls (chitin in fungi, cellulose in plants, peptidoglycan in bacteria)

Question 29

Triglycerides

Answer 29

Fat molecules (lipids) that cells construct to store energy: - Saturated fat: Solid at room temperature - Unsaturated fat: Liquid at room temperature

Question 30

Phospholipids

Answer 30

Fat molecules (lipids) that cells construct as building blocks for cell membranes and other membrane-bound organelles

Question 31

Steroids

Answer 31

Fat molecules (lipids) that have four carbon rings connected to each other (cholesterol and some hormones)

Question 32

Protein

Answer 32

Molecule made up of amino acids (20 different types); conduct most of the cellular work; used for building blocks for cell walls, cell membranes, flagella, cilia, and organelles; used as enzymes that allow cells to create chemical reactions

Question 33

Nucleic Acids

Answer 33

Made up of nucleotides (1000s - 1000000s); DNA, RNA, ATP

Question 33

Enzymes

Answer 33

Proteins that function as biological catalysts, facilitating the conversion of a substrate into a product; specific to one type of substrate; end in -ase

Question 34

Catalyst

Answer 34

A substance that speeds up the rate of a chemical reaction without being altered or depleted in the process

Question 35

Active Site

Answer 35

Small crevices on enzymes that allow a substrate to precisely bond to it

Question 36

Enzyme-Substrate Complex

Answer 36

The temporary binding of an enzyme and a substrate which lowers the activation energy for a reaction

Question 37

Cofactors

Answer 37

An inorganic substance (minerals) that loosely attach to enzymes and complete the active site; without them, enzymes cannot function correctly and normal metabolism is impaired

Question 38

Coenzymes

Answer 38

Organic substances (vitamins) that attach to enzymes and complete the active site; without them, enzymes cannot function correctly and metabolism is impaired

Question 39

Environmental Factors That Can Disrupt the Normal Shape and Function of Enzymes

Answer 39

- Temperature: speeds up or slows down the rate of reactions; too high temperatures denature enzymes - Salt concentration: most operate best at low concentrations - pH: best at values slightly above 7

Question 40

Allosteric Regulation

Answer 40

The temporary binding of regulatory molecules to the allosteric site of an enzyme

Question 41

Feedback Inhibition

Answer 41

The end product of a chemical reaction serves as an allosteric inhibitor

Question 42

Competitive Inhibition

Answer 42

An inhibitor molecule binds to the active site of an enzyme and prevents the true substrate from binding

Question 43

Non-Competitive Inhibition

Answer 43

An inhibitor molecule binds to the allosteric site of an enzyme and permanently changes the shape of the enzyme