2.2: Fundamentals and Water

Question 1

What is molecular biology?

Answer 1

explains living porcesses in terms of the chemical substances involved
- heart of molec bio is relationship between genes and protein

Question 2

the reductionist approach?

Answer 2

molectular biology is reductionist as it involves looking at various biochemical processes and breaking then down into their component parts

Question 3

chemical bonds?

Answer 3

forces that hold atoms together and form compounds
- ionic
- covalent
- polar-covalent

Question 4

electronegativity?

Answer 4

the greater affinity for electrons, the greater the electronegativity of the element
- noble gases have zero electronegativity

Question 5

intramolecular forces?

Answer 5

bonds that hold atoms togetehr in a molecule
- difference in electronegativity of two elements determines type of bond formed

Question 6

non-polar covalent bonding

Answer 6

electrons are equally shared
EM<0.4

Question 7

polar covalent bonding

Answer 7

electrons are shared unequally
0.4<EM<1.7

Question 8

ionic bonding

Answer 8

electrons are transferred
1.7<EM

Question 9

abt ionic bonding

Answer 9

• between metals and non-metals
• EM>1.7
• atoms lose ions = cations
• atoms gain electrons = anions
• very strong electrostatic force of attraction between oppositely charged ions

Question 10

abt polar covalent bonding

Answer 10

• created when electrons are shared unequally between two atms
  partial charges are indicated

Question 11

abt non-polar covalent bonds

Answer 11

• occurs when bond is formed between two atoms of same element or elements
• HOFBrINCl

Question 12

carbon tetrachloride: polar or non-polar?

Answer 12

covalent bonds can be polar or non-polar but because of the molecular shape (diapoles cancel due to their opposite directions) the overal molecule is non-polar

Question 13

symetrical molecules polarity?

Answer 13

they are polasr if all atoms surrounding central atom are the same

Question 14

polar molecules?

Answer 14

have asymetric distribution of charge
- lone pairs
- not same atoms surrounding central molecule
- overall charge is higher on one side than the other

Question 15

importance of water?

Answer 15

abundant in all life forms
- 2/3 of brain contains water
- controls many body functions
- can dissolve many substances, good for chem reactions and transporting materials

Question 16

water?

Answer 16

formed by covalent bonds between O and H atoms
- unequal sharing of electons creating polar covalent bond
- have partial positive and negative charge
- bent molecules with both H on one pole and O on other pole

Question 17

hydrogen bonding?

Answer 17

when the positive pole of water is attracted to the negatuve pole of another (this is a diapole-diapole force)
- not really a force but a intermolecular force of attraction
- relatively weak on their own but many h2o molecules showing this at once gives water unique properties

Question 18

H bonds and properties of water?

Answer 18

• strong evidence for hydrogen bonds but remains a theory
• useful way of explaining cohesive, adhesive, thermal and solvent properties of water
• assume this theory is correct as it has yet to be falsified

Question 19

cohesive properties of water

Answer 19

cohesion= binding together two molecules of same type
- water molecules can “stick to each other due to hydrogen bonding
applications:
- water transported through xylem of plant from roots to leaves, water sticks to each other making easier transporation
- high surface tension for water striders to “walk” water

Question 20

adhesion properties of water

Answer 20

for hydrogens bonds to other polar molecules, sticking to them
- sllows for water to be transported through a plant, water clings to cellulose in cells walls, helps “creep” up vessel
- allows water to cling to surfaces

Question 21

thermal properties of water

Answer 21

high specific heat capacity
- hydrogen bonds restrict movement of water molecules making it need more energy to weaken these attractive forces, thus more heat energy is needed to increase temperature of water
- allows water to stay relatively stable (good for aquatic habittats)
high latent heat of vaporization
- requires more energy to vaporize
- endothermic reation takes energy away from system, effective to remove excess heat (ie sweating as coolant)

Question 22

solvent properties of water

Answer 22

• universal solvent, can dissolve all polar molecules and aids in ion dissociation by forming shell around them, seperating them in solution
• anything that dissolves in water = soluble

Question 23

water: hydrophobic and hydrophillic interactions

Answer 23

hydrophobic
- non polar, cannot dissolve in water but maybe soluble in other substances
- these molecules tend to join togethr in water (ie. oil particles in water)
- ex. lipids, fats, oils
hydrophillic
- all substances soluble in water, polar molecules
- ex. molecules that water “sticks” to (cellulose), glucose

Question 24

transport of molecules in blood plasma: NaCl

Answer 24

ionic, freely soluble in water
- dissolves to form Na+ and Cl- ions in plasma

Question 25

transport of molecules in blood plasma: amino acis

Answer 25

amino acis have both negative and positive charges
- soluble enough to be carried in plasma
- degree of solubility depends on R group (whether side chain is hydrophobic of hydrophillic)

Question 26

transport of molecules in blood plasma: glucose

Answer 26

polar and freely soluble

Question 27

transport of molecules in blood plasma: oxygen

Answer 27

is non-polar but can dissolve because of its small size
- will reach a saturation point at low concentrations
- when temperature increases, solubility of O2 increases
- not enough O2 needed for cellular respiration at 37 degrees so hemogoblin helps, increases capacity of blood for O2 transport (has 4 O2 binding sites)

Question 28

transport of molecules in blood plasma: fat molecules and cholesterol

Answer 28

• transported in a lipoprotein complex (micelle with tryglyceride molecules inside) that has phospholipid hydrophillic heads out and hydrophobic tails in
• fats: non polar, large, insoluble, carried inside the lipoportein complex
• carbohydrates: positioned in micelle membrane so its hydrophophillic portion faces out and hydrophobic portion faces in

Question 29

water vs methane

Answer 29

Similarities:
- Comparable size and weight (H2O = 18 dalton ; CH4 = 16 dalton)
Comparable valence structures (both have tetrahedral orbital formations, but water is bent due to unbonded electron pairs)

Differences:
- Water is polar and can form intermolecular hydrogen bonds (due to high electronegativity of oxygen atom)
- methane is non-polar and can only form weak dispersion forces between its molecules
- Water has a significantly higher melting and boiling point
- Water has a higher specific heat capacity
- Water has a higher heat of vaporisation
- Water as a higher heat of fusion

Question 30

water as a coolant in sweat

Answer 30

• The change of water from liquid to vapour (evaporation) requires an input of energy
• This energy comes from the surface of the skin when it is hot, therefore when the sweat evaporates the skin is cooled
• Because water has a high specific heat capacity, it absorbs a lot of thermal energy before it evaporates
• Thus water functions as a highly effective coolant, making it the principal component of sweat