Lecture 2: Chemistry Review

Question 1

summarize the structure of an atom

Answer 1

Atoms: smallest unit of matter
1. Neutrons: no charge, mass = around 1 Dalton
2. Protons: positive charge, mass around 1 Dalton
3. Electrons: negative charge, mass around 0.0005 Dalton

Question 2

atomic mass, atomic number, isotopes

Answer 2

Atomic mass: sum of protons and neutrons
Atomic number: number of protons in atom
Isotopes: same number of protons but different # of electrons

Question 3

ionic vs. covalent bonds

Answer 3

1. Ionic Bonds (formed between ions to fill valence shells)
2. Covalent Bonds (shared electrons)
   - Single Bond: one pair of shared electrons
   - Double Bond: two pairs of shared electrons

Question 4

predict the polarity of a molecule

Answer 4

The attraction of a particular atom’s electrons in a covalent bond is called its electronegativity
Non-polar covalent bonds: electrons shared equally due to same electronegativity
Polar covalent bonds: unequally shared electrons

Question 5

how does pH relate to hydronium and hydroxide concentrations

Answer 5

hydroxide ion (OH-): negative charge
-> as the solution becomes more basic (more OH-), pH increases
hydronium ion (H3O+): positive charge
-> as the solution becomes more acidic (more H3O+), pH decreases

Question 6

why is water essential to life? four emergent properties

Answer 6

1. water molecules are able to stay together
2. water moderates temperature (specific heat capacity)
3. solid ice is less dense than liquid water
4. water is the solvent of life

Question 7

cohesion/adhesion:

Answer 7

Cohesion: the linking together of water molecules via hydrogen bonding
Adhesion: clinging together of one substance to another

Question 8

solution/solvent/solute

Answer 8

Solutions are homogenous mixtures of two+ substances
Solvent: does the dissolving
Solute: the thing being dissolved

Question 9

hydrophilic/hydrophobic:

Answer 9

Hydrophilic: water-loving
Hydrophobic: water-hating, repels water

Question 10

why is carbon the base of all organic molecules

Answer 10

carbon’s ability to form stable bonds with many elements, including itself, only 6 electrons so can form up to 4 bonds at a time with one single carbon

Question 11

isomers

Answer 11

the same number of atoms of the same elements but different structures
Structural isomers: straight vs. branched, the longer the chain = the more chance of structural differences
Cis-trans isomers: same atoms, different angles (rotation)
Enantiomers: mirror images

Question 12

Hydroxyl group (-OH):

Answer 12

Chemically reactive, Hydrophilic
Polar due to electronegative oxygen, hydrogen bonds with water

Question 13

Carbonyl group (>C=O):

Answer 13

Chemically reactive, Hydrophilic
Sugars with ketone group are called ketoses, and those with aldehydes are called aldoses

Question 14

Carboxyl group (-COOH):

Answer 14

Chemically reactive, Hydrophilic
It acts as an acid since the covalent bond between O and H is so polar

Question 15

Amino group (-NH2):

Answer 15

Chemically reactive, Hydrophilic
Acts as a base

Question 16

Sulfhydryl group (-SH):

Answer 16

Chemically reactive, Hydrophobic
(2 can form disulphide bonds)

Question 17

Phosphate group (-OPO3 ^2-):

Answer 17

Chemically reactive, Hydrophilic
- Contributes negative charge

Question 18

Methyl group (-CH3):

Answer 18

Chemically unreactive, Hydrophobic
- Affects the expression of genes when on DNA or proteins
Recognizable tag on biomolecules

Question 19

monomers

Answer 19

a long molecule consisting of similar/identical building blocks (Proteins, Carbohydrates, Fats/Phospholipids, Nucleic Acids)

Question 20

polymerization

Answer 20

the creation of polymers -> facilitated by enzymes that speed up reactions

Question 21

dehydration reactions

Answer 21

covalently bond two monomers together, losing water in the process

Question 22

hydrolysis reactions

Answer 22

disassemble polymers into monomers -> bond = broken by water