Unit 2 - Plasma membranes

Question 1

Define phospholipid bilayer

Answer 1

-arrangement of phospholipids found in cell membranes
-the hydrophilic phosphate heads form the inner and outer surface of a membrane ,
-sandwhiching the fatty acid tails to form a hydrophobic core

Question 2

Why are membranes referred to as having a ‘fluid-mosaic structure’ ?

Answer 2

-the phospholipids are able to move freely relative to each other (fluid)
-the proteins embedded in the bilayer vary in shape, size, and position (mosaic)

Question 3

What are membrane proteins?

Answer 3

Proteins that provide a hydrophilic channel through a membrane

Question 4

What are the functions of phospholipids in cell surface membranes?

Answer 4

-forms basic structure
-acts as partially permeable barrier
-allows the passage of lipid soluble molecules
-prevents water soluble molecules from moving across

Question 5

What are the functions of carrier proteins in cell surface membranes?

Answer 5

-have an important role in both passive movement of polar molecules and ions down a concentration gradient
-this involves the shape of the protein changing

Question 6

Why does an increase in temperature increase membrane permeability?

Answer 6

-more temperature means phospholipids move more
-because they have a higher kinetic energy
-makes it easier for things to pass through