Molecules

Question 1

unsaturated

Answer 1

fatty acid with a carbon-carbon double bond

Question 2

Explain how the properties of water are significant to living organisms.

Answer 2

1. water is transparent / light passes through water;
2. this allows organisms to live below the surface / plants to photosynthesize;
3. hydrogen bonds between water molecules make water cohesive;
4. this gives water a high surface tension allowing animals to live on the surface / maintains lung structure (pleural membranes);
5. helps in water movement through plants/transpiration;
6. water has a high latent heat of vaporization / OWTTE;
7. evaporation/sweating/transpiration leads to cooling;
8. water has a high specific heat capacity / OWTTE;
9. this provides a stable environment for water organisms;
10. water is a universal solvent; can transport materials around organisms/plants/animals;
11. can be a solvent for chemical reactions in organisms;
12. ice is less dense than water / water has a maximum density at 4°C surface (pond/lake/ocean) freezes first, allowing organisms to survive in the water below;
13. hydrogen bonds between water and other substance makes water adhesive

Question 3

Explain how the properties of phospholipids help to maintain the structure of cell membranes.

Answer 3

1. (labelled) phospholipid consisting of head and two tails;
2. head is glycerol and phosphate;
3. tails are fatty acid chains;
4. head hydrophilic and tails hydrophobic;
5. hydrophilic molecules/heads attracted to/soluble in water;
6. hydrophobic molecules/tails not attracted to water but attracted to each other;
7. (properties of phospholipids leads to) formation of double layer in water;
8. stability in double layer because heads on outer edge are attracted to water and tails are attracted to each other in middle;
9. phospholipid bilayer in fluid/flexible state because of attraction of non-polar tails to each other;
10. (fluidity) allows membranes to change shape/vesicles to form or fuse with membrane/(fluidity) allows cells to divide;
11. non-polar amino acid side chains attracted to (hydrophobic) tails;

Question 4

Which different carbohydrate molecules have which different linkages?

Answer 4

glucose 1,4 glucose : maltose
glucose 1,6 glucose : isomaltose
poly-1,4-ALPHA-glucose : amylose
poly-1,4-BETA-glucose : cellulose
poly-1,4-ALPHA-glucose w/ 1,6 branches : amylopectin, glycogen

Question 5

Explain the relationship between the properties of water and its uses in living organisms as a coolant, a medium for metabolic reactions and a transport medium.

Answer 5

1. water is a polar molecule;
2. oxygen has a partial negative charge / hydrogen has a partial positive charge;
3. hydrogen bonds form between adjacent water molecules;
4. water remains liquid over wide range of temperatures/0 to 100 °C ;
5. moderates temperature fluctuation / stable environment;
6. accurate reference to specific heat;
7. sweating/evaporation cools organisms;
8. accurate reference to high heat of vaporization;
9. polarity makes water a good/universal solvent for polar/ionic substances;
10. (all) metabolic reactions of cells take place in (aqueous) solutions;
11. blood/xylem/phloem transport solutes in water;
12. cohesive properties allow capillary action/transpiration stream/water column in xylem;