Adaptaions to specific environmental conditions

Variation in lipid compositions among cell membranes

Ability to change the lipid composition in response to temp changes has evolved in organisms that live where

Temperatures may vary

What is a membrane?

- Acollage of different proteins
-grouped together
-embedded in the fluid matrix of the lipid bilayer

What do proteins determine?

most of the membranes specific functions

Peripheral proteins are bound to what?

The surface of the membrane

Integral proteins penetrate

The hydrophobic core.

What are trans membrane proteins?

Integral proteins that span the membrane

The hydrophobic regions of proteins consist of what?

One or more stretches of non polar amino acids, often coiled in alpha helices

What are six major functions of membrane proteins?

-transport
-enzymatic activity
-signal transductions
-cell-cell recognition
-intercellular joining
-attachment to the cytoskeleton and extracellular matrix (ecm

Cells recognize each other by?

binding to surface molecules

What do surface molecules often contain

carbohydrates on the extracellular surface of the plasma membrane

Membrane carbohydrates may be covalently bonded to?

Lipids (forming glycolipids)
Or More commonly to proteins (forming glycoproteins)

carbohydrates on the external side of the plasma membrane vary among?

species, individuals, and even cell types in an individual