Phospholipid Bilayer question

G O D I V A

Membranes are made up of a phospholipid bilayer. What is the use/function of:

•

cholesterol

•

glycoprotein

•

integral proteins embedded in the phospholipid bilayer

I'm revising for an exam in 2 days so please help

Reply 1

Hobnobs Galore

Cholesterol molecule straightens out hydrocarbon chains. Glycoprotein- for communication and transport (i think)

and proteins for transport- eg carrier proteins

Reply 2

BillyMarsh

Glycoproteins branch off into the surrounding fluids and stabilise the cell.
They are also used for intracellular messaging (Antigens specifically).

The embedded proteins could be carrier proteins / protein channels which are used in Active Transport in and out of the cell i.e. Na+ or they could be enzymes such as ATPase.

Cholesterol maintains mechanical stability.

Reply 3

Malsy

Cholesterol; to stabilise the bilayer as it would be too fluid without it.
Glycoproteins; to act as receptors(I think)
Integral Proteins: ion pores(to transport ions) or transport proteins(to carry glucose and amino acids)

Reply 4

Hobnobs Galore

Lol this thread proves how long ago it was since i did biology a-level!

Reply 5

Malsy

Hobnobs Galore

Lol this thread proves how long ago it was since i did biology a-level!

Lol. count yourself lucky; it's a nightmare.

Reply 6

kc-raine

cholesterol stablises the membrane.
glycoproteins are used as receptors i think.
other proteins are used as carriers or to create channels to help transport ions/molecules across the membrane.

hope it helps a bit!

Reply 7

BillyLiu

G O D I V A

Membranes are made up of a phospholipid bilayer. What is the use/function of:

•

cholesterol

•

glycoprotein

•

integral proteins embedded in the phospholipid bilayer

I'm revising for an exam in 2 days so please help

I'll help myself helping you by doing this :smile:

Interview tomorrow in Cambridge - might come up:

Cholesterol does maintain membrane fluidity - it increases fluidity at lower temperature, and vice versa at higher temperatures. The mechanism is that it acts as a wedge to seperate the phospholipid a little, thereby reducing Van Der Waals bonding and also increasing permeability to molecules.

Glycoprotein acts as cell recognition proteins - "self and non self" really.

Integral proteins -
Carrier proteins - actively transport molecules across the membrane against a concentration gradient (e.g. Na - K pump).

Protein Channels - provides a hydrophilic channel through which water solutes can diffuse through, though the protein is specific [question to others: am I right in saying this is facilitated diffusion?]

Protein Receptors - a ligand attaches to the substrate of the protein on one end, and the other end sends a cascade signal inside the cell, expressing or inhibiting a certain gene from T&T a protein.

Cell Adhesion - certainly some attach to the cytoskeleton inside the cell, and attach to other cell membranes.

lol, wall of text there. Hope this helps! :biggrin: