Lecture 4

Question 1

What is the basic structure of the generalized plasma membrane postulated by Singer and Nicholson?

Answer 1

the basic cell membrane consists of a phospholipid bilayer that has proteins and glycoproteins embedded or attached.

Question 2

How are phospholipids arranged in the plasma membrane?

Answer 2

The phospholipids are arranged with their hydrophilic tails facing eachother, while their hydrophobic heads face outwards.

Question 3

Which phospholipids are found in the outer leaflet?

Answer 3

• cholesterol
• phosphatidylcholine
• phosphatidylethanolamine
• sphingomyelin
• glycolipids
• glycosylphosphatidylinositol

Question 4

Which phospholipids are found in the inner leaflet?

Answer 4

• glycosylphosphatidylinositol
• phosphatidylethanolamine
• cholesterol
• phosphatidylserine

Question 5

What are the functions of glycolipids and where are they located within the plasma membrane?

Answer 5

• Glycolipids are located in the outer leaflet
• they create a cell coat involved in cell-to-cell interactions
• convey antigenicity

Question 6

What are lipid rafts?

Answer 6

lipid rafts are small patches of cholesterol and sphingolipids that compartmentalize cellular processes by serving as organizing centers

Question 7

What is the glycocalyx, where is it located and what does it do?

Answer 7

The glycocalyx is a carbohydrate coat on the extracellular surface of the cell membrane.

• It serves as a barrier against microorganisms
• cell-to-cell interactions
• protects cell rom ionic and mechanical stress

Question 8

How can you differentiate between peripheral and integral proteins?

Answer 8

• peripheral proteins are found on the outer and inner leaflets of the cell membrane, they can be removed easier than integral proteins by changing the ionic concentrations or pH
• integral proteins are embedded in the bilayer

Question 9

Describe the characteristics of transmembrane proteins.

Answer 9

• Transmembrane proteins are integral proteins that pass all the way through both phospholipid bilayers.
• they function as channel and transporter proteins

Question 10

What are the major mechanisms for moving materials across cell membranes?

Answer 10

• diffusion
• osmosis
• facilitated diffusion
• active transport

Question 11

Which mechanisms are energy dependent?

Answer 11

Active transport is the only mechanism that requires energy

Question 12

Which mechanisms require transporters?

Answer 12

Facilitated diffusion requires transport molecules

Question 13

What are the three transport proteins?

Answer 13

• Unitransporters
• Symporters
• Antiporters