Lectures 1 & 2

Question 1

Mass Number

Answer 1

number of protons + neutrons

Question 2

Atomic Number

Answer 2

number of protons

Question 3

Covalent Bond

Answer 3

• Made of 2 electrons
• Those 2 electrons are shared (i.e. one electron comes from each atom)
• Atoms can form bonds until their outermost shell is filled

Question 4

Polar Covalent Bonds in water molecules

Answer 4

electrons are not shared equally (O is more electronegative than H), so partial charges exist on the O and H atoms

Question 5

Increasing positive electrical charge in nucleus

Answer 5

H < C < N < O < F

Question 6

Hydrogen Bond

Answer 6

A hydrogen bond is an electrostatic attraction between two polar groups that occurs when a hydrogen (H) atom, covalently bound to a highly electronegative atom such as nitrogen (N), oxygen (O), or fluorine (F)

Question 7

Meniscus

Answer 7

forms where water meets a solid surface,
as a result of two forces.
Adhesion: Water
molecules that adhere
to the glass resist the
downward pull of
cohesion
Cohesion: Water
molecules at the
surface experience a
net downward pull
from hydrogen bonds
with water molecules
below

Question 8

High Surface Tension

Answer 8

Property of Water
- Because of surface
tension, light objects
do not fall through the
water’s surface

Question 9

Ice

Answer 9

Water molecules form a crystal lattice.

Question 10

Liquid water

Answer 10

• No crystal lattice forms.
• Denser than ice. As a result,
  ice floats.

Question 11

Ionic Bond

Answer 11

• Electrostatic attraction between positive and negative charge
• Forms ions

Question 12

Hydrophilic

Answer 12

Water loving

a) Polar molecules and ions dissolve readily in water
- partial negative and positive charges of water interact with the positive and negative ions
ex. salt dissolved in water, ions separate then dissolve

Question 13

Hydrophobic

Answer 13

Water Fearing
b) Nonpolar molecules do not dissolve in water.
cannot interact with water, so they stay away
ex. Water and oil

Question 14

Hydrophobic interaction

Answer 14

Water forces nonpolar molecules together, because doingso minimizes their disruptive effects on the hydrogen-bonded water network
- important for protein folding

Question 15

Van der Waals interaction

Answer 15

Nonpolar molecules are also attracted to each other via relatively weak attractions called van der Waals forces (transient dipoles).

Question 16

Bond Energy

Answer 16

Amount of energy needed to separate two bonded or interacting atoms under physiological conditions

Question 17

Chemical bonds in order of strength in biology

Answer 17

Covalent > H bond > Ionic Bond > Hydrophobic interaction > LDF

Question 18

Chemical Reactions

Answer 18

A chemical reaction can be written as an equation. The equation must balance because matter is neither created nor destroyed.

Question 19

Molarity

Answer 19

A 1 molar (1 M) solution is one mole of a compound dissolved in water to make one liter.
Example: One mole of NaCl is the atomic weight of Na (23) plus the atomic weight of Cl (35.5), or 58.5, in grams. When 58.5 grams of NaCl are dissolved in water to make one liter, the solution is 1 molar.

Question 20

Mole

Answer 20

• amount of a substance in grams whose weight is equal to its molecular weight.

Question 21

Acids

Answer 21

release/donate H+ ions in solution.
If the reaction (dissociation) is complete, it is a strong acid, such as HCl.
The carboxyl group (—COOH) is common in biological compounds. It functions as a weak acid because it dissociates partially and reversibly
—COOH —COO– + H+

Question 22

Bases

Answer 22

• accept H+ in solution (release OH–). (takes protons from water)
• NaOH ionizes completely to Na+ and OH–. The OH– absorbs H+ to form water. It is a strong base.
• The amino group (—NH2) is an important part of many biological compounds; it functions as a weak base by partially and reversibly accepting H+:
  —NH2 + H+ —(NH3)+

Question 23

pH

Answer 23

defined as the negative logarithm of the H+ concentration in moles/liter
1 (very acidic) -14 (very basic)
7- neutral (water)