Ch 2 The Study of Structure of the Plasma Membrane

Question 1

What are the functions of membrane?

Answer 1

• Compartmentalization (enclosed the cell contents and intracellular spaces)
• scaffold for biochemical activities
• providing a selectively permeable barrier (prevent unrestricted exchange)
• transporting solutes
• responding to external signals
• intercellular interaction
• energy transduction

Question 2

What is the content of fluid-mosaic model of membrane?

Answer 2

Phospholipids, glycolipid, Cholesterol

Question 3

What are liposome and its usage?

Answer 3

Phospholipid bilayers that have closed in upon themselves to form a tiny bubble, or vesicle.

1. Membrane proteins can be inserted into liposomes and their function studied in a much simpler environment than that of a natural membrane.
2. Liposomes have been developed as vehicles to deliver drugs or DNA molecules within the body

Question 4

Which two styles do membrane carbohydrates exist in?

Answer 4

Glycoproteins and glycolipids

Question 5

Which orientation do carbohydrate of the plasma membrane face? Outward or inward?

Answer 5

outward

Question 6

Mammal’s glycolipid exist in glycosphingolipid or glyceroglycolipid?

Answer 6

glyceroglycolipid

Question 7

What are the differences of oligosaccharides between glycolipid and glycoprotein?

Answer 7

The carbohydrate of glycoproteins is present as short, branched oligosaccharides, typically having fewer than 15 sugars per chain.
Oligosaccharides may be attached to several different amino acids by two major types of linkages.

Question 8

Which three groups can membrane proteins divided into?

Answer 8

Integral proteins, Peripheral proteins, Lipid-anchored proteins

Question 9

Which group membrane proteins are definitely movable?

Answer 9

integral proteins able to move laterally within itself

Question 10

How many factors are related with membrane physical state?

Answer 10

1) phospholipids with saturated fatty acids tend to have higher transition temperature；those with unsaturated chains are opposite；the introduction of one double bond in a saturated fatty acid lowers the melting temperature almost 60 centigrade
2) the shorter the fatty acyl chains of a phospholipid, the lower its melting temperature
3) cholesterol molecules disrupt the close packing of fatty acyl chains and interfere with their mobility，the presence of cholesterol tends to abolish sharp transition temperatures and create a condition of intermediate fluidity

Question 11

What strategies do cell have to maintain membrane fluidity in relative low temperature?

Answer 11

• desaturating single bonds in fatty acyl chains to form double bonds
• reshuffling the chains between different phospholipid molecules to produce ones that contain two unsaturated fatty acids, which greatly lowers the melting temperature of the bilayer

Question 12

Conception: lipid raft

Answer 12

Specialized region or microdomain process distictive lipid composition ,cholesterol and sphigolipid, that are more gelated and highly ordered than surrounding regions

Question 13

What are the four different processes in which substances move across membrane?

Answer 13

1. simple diffusion through the lipid bilayer
2. simple diffusion through an aqueous, protein-lined channel
3. diffusion that is facilitated by a protein transporter
4. active transport，which requires an energy-driven protein “pump” capable of moving substances against a concentration gradient

Question 14

What kinds of solutes can pass through membrane by simple diffusion?

Answer 14

small inorganic molecules such as O2、CO2、NO（nitrogen monoside ）、and H2O
small fat-soluable molecules, such as glycerol, ethanol

Question 15

What kind of passive transport has the highest efficiency?

Answer 15

Facilitated diffusion

Question 16

What are the characters of active transport?

Answer 16

Requires energy (ATP)
Active transport proteins are highly selective
Active transport is needed for proper functioning of nerves and muscles

Question 17

Cotransport belongs to active transport or passive transport?

Answer 17

Active transport