LECTURE 4

Question 1

Plasma membranes are

Answer 1

Selectively permeable

Question 2

What is the basic structure of all biological membranes

Answer 2

Spherical phospholipid bilayer

Question 3

Membranes are made of

Answer 3

Proteins and lipids

Question 4

Fluid mosaic model

Answer 4

Membrane is a fluid structure with a ‘mosaic’ appearance cuz of different types of proteins in it.

Question 5

Proteins in the bilayer can be classified in two groups

Answer 5

1) integral

2) peripheral

Question 6

Integral proteins

Answer 6

Embedded in the bilayer, at least one portion of the protein is hydrophobic

Question 7

Peripheral proteins

Answer 7

Attached loosely to the surface of the membrane

Question 8

Membranes consign other components:

Answer 8

• glycoproteins
• Glycolipids
• cholesterol

Question 9

Glycoproteins

Answer 9

• membrane proteins that have a sugar attached

- important function in cell recognition.

Question 10

Glycolipids

Answer 10

membrane lipids that have a sugar attached

Question 11

Cholesterol

Answer 11

• inserts between phospholipid molecules.

- influences membrane permeability and fluidity.

Question 12

Biological membranes are fluid at

Answer 12

physiological temps

Question 13

Phospholipids are able to move _______ but rarely ever move _______

Answer 13

Laterally Transversely

Question 14

High temps increase

Answer 14

Fluidity in membranes

Question 15

At higher temps, the membrane becomes more

Answer 15

Permeable

Question 16

Is the temp is low enough, the membrane will turn

Answer 16

Solid (phase transition)

Question 17

Length of fatty acids in the phospholipids

Answer 17

Short chains have less stable interaction then long Chains. Therefore, lower temp required to make short chain into solids.

Question 18

What is the shape of fatty acids in the phospholipids influenced by

Answer 18

double bonds,

Question 19

Unsaturated fatty acids in phospholipids

Answer 19

Double bonds cause structural kinks, decreasing ability of chains to pack together

Question 20

How does Cholesterol maintain membrane fluidity

Answer 20

Fluidity buffer at a greater range of temps

Question 21

What does cholosterol interfere with

Answer 21

Lateral movement of phospholipids, causing a reduction in ,embrace fluidity at moderate temps.

Question 22

What does cholosterol prevent

Answer 22

Close packing of phospholipids at low temps, (solidification)

Question 23

Animals have _____ of cholesterol and plants have ________ cholesterol in their membranes

Answer 23

A lot. Little

Question 24

Six major function of membrane proteins

Answer 24

1) transport of molecules in or out of cells
2) enzymatic reactions near the membrane
3) signalling via receptors
4) c ell-cell recognition
5) intercellular attachment
6) attachment of the extra cellular matrix proteins