a1.1- water

Question 1

why is water a medium for life

Answer 1

• first cells originated in water
• where most life processes occur

Question 2

physical properties [9]

Answer 2

1. high specific heat capacity
   - takes a lot of energy to break H+ bonds
2. high latent heat of vaporisation
3. good coolant
4. good solvent
   - medium for metabolic reactions
5. transport medium
   - dissolves nutrients, gases and waste products
6. dense
   - can support the mass of large and small organisms
   - ice is less dense: life on top and below
7. buoyancy
   - float
8. viscosity
9. thermal conductivity

Question 3

organisms in water examples x2 [3]

Answer 3

black-throated loon
1. oiled feathers- water has greater thermal conductivity than air
2. large wings- generate lift in less buoyant air
3. hydrodynamic- reduce drag against viscosity

ringed seal
1. low density blubber- increases buoyancy
2. insulating blubber- reduce heat loss
(higher specific heat capacity, temperature is more stable)
3. streamlined shape: against viscosity

Question 4

why is water polar

Answer 4

• due to unequal sharing of electrons
• imbalance of charges
• hydrogen bonding due to polarity
  *bonds diagram

Question 5

reason for cohesion of water molecules + application

Answer 5

due to hydrogen bonds
1. transport of water under tension in xylem
2. use of water surfaces as habitats- surface tension

Question 6

adhesion of water to material that are polar + application

Answer 6

Attraction to charged or polar surfaces (such as cellulose cell walls) allows water to flow in opposition to gravitational forces (capillary action)

Question 7

solvent properties of water

Answer 7

• hydrophilic molecules dissolve in water
• most enzymes catalyse reactions in aqueous solution
• some functions of cells depend on them being hydrophobic and insoluble

Question 8

origin of water

Answer 8

• from extra-planetary objects
• ice asteroids maybe from asteroid belt
• other asteroid knocks out asteroid belt- to us
• large asteroids at least few hundred kilometers so it would still be ok after ozone

Question 9

reasons for water retention [2]

Answer 9

1. earths gravity prevents water form escaping the planet
2. temperature is cool enough to condense water

Question 10

relationship between the search for extraterrestrial life and the presence of water

Answer 10

• universal solvent
• important for transport medium within a cell

Question 11

adhesion

Answer 11

water molecule is able to stick to other polar or charged molecules via the formation of polar associations

Question 12

cohesion

Answer 12

• ability of like molecules to stick together
• forms h bonds

Question 13

hydrophilic

Answer 13

• water loving
• polar
• charged

Question 14

examples of hydrophilic substances [2]

Answer 14

1. glucose
2. minerals

Question 15

hydrophobic

Answer 15

• repels water
• non-polar
• non-charged

Question 16

examples of hydrophobic substances [2]

Answer 16

1. fat
2. oil

Question 17

goldilocks zone

Answer 17

• habitable zone
• range of distance form a star with the right temperatures for water to remain liquid

Question 18

signs of water in space

Answer 18

spectroscopy
- analyses the wavelengths of light emitted or absorbed by a substance
- used to detect the presence of water molecules in space

Question 19

other factors that contribute to look for extraterrestrial life

Answer 19

1. carbon
2. nitrogen
3. suitable temperature

Question 20

phospholipid bilayer

Answer 20

hydrophilic head
- glycerol and a phosphate molecule
hydrophobic tail x2
- fatty acid (hydrocarbon) chains

Question 21

properties of the phospholipid bilayer

Answer 21

• held together by weak hydrophobic interactions between the tails
• individual phospholipids can move within the bilayer: allows fluidity and flexibility
• spontaneous breaking and reforming of membranes (endocytosis / exocytosis)

Question 22

fluid-mosiac model

Answer 22

fluid– the phospholipid bilayer is viscous and individual phospholipids can move position
mosaic– phospholipid bilayer is embedded with proteins, resulting in a mosaic of components

Question 23

osmolarity

Answer 23

measurement of solute concentration of a solution

Question 24

what property allows for the presence of ions, sugars, amino acids and proteins in sweat

Answer 24

solvent properties