Cell membrane and organelles

Question 1

Fluid mosaic model

Answer 1

1. phospholipid (and protein) molecules moving laterally
2. presence of embedded proteins scattered in the membrane

Question 2

effect of high temp on cell membrane

Answer 2

effect on phospholipids:
- high temps result in disruption of HI between phospholipids
- thus causing membrane to become too fluid (i.e. more transient gaps)
- (specific membrane property) and causing cell membrane to be ineffective as a barrier

effect on proteins:
- high temps result in denaturation (i.e. loss of 3d conformation) of proteins
- through breakage of H bonds, ionic bonds and HI
- (specific protein function) thus resulting in non-functional transport protein / no more enzyme activity / …

Question 3

protein synthesis at rER

Answer 3

1. bound ribosomes on rER synthesise polypeptide
2. synthesised polypeptide is then passed through rER membrane
3. and into the rER lumen for folding and packaging into vesicles
4. transport vesicles containing folded polypeptide pinch/bud off rER

Question 4

protein synthesis at Golgi body/apparatus

Answer 4

1. modification/glycoslylation of protein,
2. which is then packaged/sorted at the cell surface for secretion
3. bud off as secretory vesicles,
   which then move towards and fuse with plasma membrane,
   resulting in the release of contents via exocytosis

Question 5

process of exocytosis

Answer 5

1. (a) movement of vesicles to the cell surface membrane
   (b) and fusion of membrane of vesicle with cell surface membrane
2. thus emptying vesicle contents into extracellular region

Question 6

how nutrient availability affects processes
(e.g. cell division)

Answer 6

• glucose
  -> required for aerobic respiration to release ATP
  -> used as energy required for process
• essential amino acids,
  which cannot be produced by cells and thus must be taken up from envt
  -> to synthesise important proteins needed for process