Structure and Function of Biological Membranes

Question 1

Plasma membrane

Answer 1

• Provides cell boundary & prevents movement of material in/out of cell.
• Organelle membrane divides cytoplasm into compartments
• Composed of lipids & proteins
• Highly dynamic

Question 2

Compartmentalised

Answer 2

More efficient inside eukaryotic cells as components compartmentalised eg ribosomes work best at ph5 (in cell, ph7, would be less efficient

Question 3

Membrane properties

Answer 3

-Barrier: flexible, self-repairing, continuous -Selectively permeable: only allows passage of certain molecules into/out of cell

Question 4

Membrane Composition

Answer 4

-Lipids (phospholipids, cholesterol, or other sterols) -Proteins -Carbohydrates -(Glycoproteins/Glycolipids) -Oligosaccharide chains covalently linked to protein/lipid. Made up of suger residues linked covalently in branched chains

Question 5

Phospholipids

Answer 5

~1x10^9 lipid molecules form a bilayer around a small cell, held together by non-covalent forces

• Amphipathic (contains hydrophobic &hydrophilic regions)
• Polar head group (hydrophilic) (carboxyl group (COO-))
• Hydrophobic tail (hydrocarbon tail)
• Provide the structure &permeability barrier of membranes
• Have important role in cell signalling membrane interactions

Question 6

Fatty Acids in Membrane Phospholipids

Answer 6

-Linear hydrocarbon chains -12-22 C atoms -even no. of C atoms -Saturated/ unsaturated -Unsaturated- all cis double bonds that cause ‘kink’ (not trans)

Question 7

Major Membrane Phospholipids

Answer 7

-Phosphatidylethanolamine -Phosphatidylserine (overall -ve charge) -Phosphatidylcholine -Sphingomyelin

Question 8

Cholesterol

Answer 8

-polar head group -rigid steroid ring structure -non-polar hydrocarbon tail

Question 9

In aq solution lipids form micelles/ bilayers

Answer 9

Question 10

Lipid Bilayers

Answer 10

Question 11

Experimental Uses Of Lisosomes

Answer 11

• Drug delivery
• Delivery of DNA & RNA into cells
• Cosmetic industry