Cell Membrane

Question 1

What does amphiphilic mean?

Answer 1

Molecule has a hydrophobic and hydrophilic end like phospholipids

Question 2

Common constituents of phospholipid bilayer

Answer 2

PhosphoatidylETHANOLAMINE
PhsophoaditylSERINE
PhosphoaditylCHOLINE (lecithin)
Sphingomyelin

Question 3

Why is the membrane asymmetrical?

Answer 3

Glycolipids are attached in the outside but negative charges are attached on the inside

Question 4

What is “flip flop”?

Answer 4

Movement of hydrophobic head through a hydrophilic core.
This requires too much energy so does not happen
BUT phospholipids regularly move laterally

Question 5

More protein…

Answer 5

More fluidity

E.g neurones have less protein as they are more rigid so are better insulators

Question 6

Explain the movement of Na+ and K+ across a cell membrane

Answer 6

Na+/K+ pump = one alpha and one beta chain
Alpha chain crosses membrane 10 times but beta only once
FUNCTION = maintain osmotic balance
2K+ move out for every 3Na+ move in
Concentration and charge gradient

Question 7

What is the sodium potassium pump driven by?

Answer 7

Phosphorylation of aspartyl residue and hydrolysis of aspartly phosphate

Question 8

How are glucose and amino acids transported into cells?

Answer 8

Active transport of Na+
Facilitated diffusion of amino acids and glucose using the flip-flop mechanism
Some of the mechanisms are insulin dependent