Unit 4

Question 1

Integral proteins

Answer 1

• Plasma membrane
• Penetrate & pass through lipid bilayer
• Amphipathic

Question 2

Lipid-anchored

Answer 2

• Plasma membrane
• Do not embed by protein portion. Rather, protein is linked to a lipid which embeds in the membrane. 3 Main types:
  a.) GPI-anchored
  b.) Fatty acid anchored
  c.) Isoprenylation anchor

Question 3

GPI-anchored proteins

Answer 3

• Plasma membrane
• Part of lipid-anchored category
• Protein is covalently attached to glycosylated phosphatidylinostitol
• Mainly found on external side of plasma membrane

Question 4

Fatty acid anchored protein

Answer 4

• Plasma membrane
• Part of lipid-anchored proteins group
• Protein can be attached to multiple isoprene groups. 3 such groups called fernesyl. 4 groups called geranylgeranyl. Common on small GTPases

Question 5

Peripheral proteins

Answer 5

• Plasma membrane
• Attach to membrane by weak electrostatic bonds & are easily solubilised
• Located entirely outside of bilayer on either extracellular or cytoplasmic side.
• Associate with membrane surface by non-covalent bonds
• Can be removed from membranes by agents that disrupt electrostatic interactions like high pH & high concentrations of salt

Question 6

SDS

Answer 6

• Strong ionic detergent
• Ionised group at its hydrophillic end

Question 7

Triton X-100

Answer 7

• Mild non-ionic detergent
• Non-ionised but polar group at its hydrophillic end