Intro To Cell Membranes

Question 1

What does the appearance of biological membranes differ on?

Answer 1

They differ depending on location and function

Question 2

What do plasma membranes do ?

Answer 2

They provide cell boundary and prevents movement of materials in to and out of the cells

Question 3

What do organelle membranes do ?

Answer 3

Divide cytoplasm into compartments

Question 4

What are the fundamental properties of membranes?

Answer 4

• Barrier
• Flexible, self-repairing, continuous
• Selectively permeable

Question 5

Can phospholipids move about in the bilayer?

Answer 5

Phospholipids can rotate or exchange in the lateral plane of the membrane - but normally move very slowly from one leaflet to the other

Question 6

What determines the fluidity of the lipid bilayer?

Answer 6

Its composition. The greater the number of double bonds, the shorter the acyl chains, the less tightly packed the molecules are = greater the fluidity

Question 7

What does amphipathic mean?

Answer 7

It is a molecule which has a polar and non polar region.

Question 8

What determines the fluidity of lipid bilayer?

Answer 8

No. of double bonds and No. of C atoms in the fatty acid chains of the phospholipids.

Question 9

How are phospholipids Amphipathic?

Answer 9

Polar Headgroup and hydrophobic tail.

Question 10

What state of matter are membranes at the temperature of the organism?

Answer 10

Fluids (liquid)

Question 11

Describe the composition of a cell membrane in a cold - blooded animal.

Answer 11

More double bonds and/or shorter acyl chains than membranes of warm blooded animals

Question 12

What is the net charge of Phosphatidyl serine?

Answer 12

-1

Question 13

What effects does cholesterol have on the cell membrane?

Answer 13

Makes the member less permeable.

Packs between phospholipids and makes the membrane less deformable at the surface. It does not make the overall membrane more rigid

Question 14

What does high concentrations of cholesterol do to the membrane ?

Answer 14

Prevents the membrane from becoming crystalline

Question 15

What is crystalline?

Answer 15

Solidification of membranes.

Question 16

What are formed by lipids in aqueous solutions?

Answer 16

Micelles or bilayers.

Question 17

What do lipid bilayers preferably form?

Answer 17

Sealed compartments.

Question 18

What are integral membrane proteins?

Answer 18

They are proteins that directly insert in the membrane by a hydrophobic domain.

Question 19

What are peripheral membrane proteins?

Answer 19

Peripheral membrane proteins are extrinsic membrane proteins temporarily bound with membranes which helps in cell signalling.

Question 20

What two ways can peripheral membrane proteins associate with the membrane?

Answer 20

Associate with integral membrane proteins or directly bind lipids
Covalently bound lipids which insert into the membrane

Question 21

What are micro domains?

Question 22

What do membrane lipids form?

Answer 22

Clusters or microdomain

Question 23

What forms rafts?

Answer 23

Cholesterol and sphingolipids can form micro domains called rafts.
Membrane (raft) is slightly thicker in the microdomain

Question 24

Where do tight junctions prevent movement?

Answer 24

They prevent movement between apical and baseolateral membranes

Answer 25

Flexible cytoskeleton gives red blood cells its flexibility and rigidity

Question 26

What do optical tweezers show us about the red blood cell membranes?

Answer 26

Shows us the tensile strength of red blood cell membranes

Question 27

What happens when red blood cells are placed in hypotonic solutions?

Question 28

What are red blood cell ghosts?

Answer 28

Predominantly plasma membrane (check)

Question 29

What happens when red blood cells are placed in hypertonic solutions?

Question 30

What do mutations in spectrin cause?

Answer 30

Mutations in spectrin causes certain types of hemolytic anemia

Answer 31

Integral proteins acts as anchor within the cytoskeleton (check)

Question 32

Are membranes symmetric?

Answer 32

No they are asymmetric

Question 33

When is membrane asymmetry important?

Answer 33

Coagulation
Cell recognition and clearance

Question 34

Why is O antigen a universal blood donor?

Answer 34

The structure of the O antigen will be recognised in A and B antigens

Question 35

What is coagulation?

Question 36

Is AB a universal blood acceptor or donor?

Answer 36

Universal acceptor

Question 37

Why do channels transport solute more rapidly than carriers?

Answer 37

Carrier proteins directly bind to the solute whereas channel proteins only interact very weakly with the solute

(Channels can transport 100 million ions per second)

Question 38

Suggest 3 features for the ion channels

Answer 38

Form narrow hydrophilic pores through the membranes
Are specific for different ions - e.g. potassium channel, sodium channel
Allow rapid movement of ions down the conc gradient or electrochemical gradient

Question 39

How many different types of channel are there ?

Answer 39

Over 100 different types of channel with different properties

Question 40

What does the mutation of voltage-gates sodium channel SCN9A cause?

Answer 40

It causes congenital insensitivity to pain

Question 41

What are the 3 types of carrier - mediated transport ?

Answer 41

Uniport
Symport
Antiport

Question 42

The mammalian plasma membrane is transport driven by __?

Answer 42

Sodium gradients

Question 43

Bacteria, yeast, intracellular membranes are transport driven by __?

Answer 43

Proton gradients

Question 44

Bacteria, yeast, intracellular membranes are transport driven by __?

Answer 44

Hydrogen gradients

Question 45

Glucose uptake is driven by ___?

Answer 45

An electrochemical gradient

Question 46

Describe the 3 types of transport of glucose at a transcellular level

Answer 46

Glucose/sodium ion symporter at the apical surface
Sodium/Potassium pump at the basal surface
Glucose carrier at the basal surface