Biological Membranes

Question 1

What are the properties of a fluid mosaic model

Answer 1

Is a bilayer of amphipathic lipids
Has proteins: integral, peripheral, lipid anchored
Components are mobile
Components can interact

Question 2

What 4 properties are shared by all membranes

Answer 2

~6 nm thick
Stable
Flexible
Capable of self assembly

Question 3

What three classes of membrane proteins

Answer 3

Integral
Lipid anchored
Peripheral

Question 4

What is membrane fluidity determined by

Answer 4

Nature of lipid in the membrane

Temperature

Question 5

What increases membrane fluidity

Answer 5

Unsaturated lipids

Warming

Question 6

What decreases membrane fluidity

Answer 6

Cooling

Saturated lipids

Question 7

What is a transition temperature

Answer 7

The temperature at which the membrane enters a crystalline gel state

Question 8

Why is membrane fluidity crucial to cell function

Answer 8

Brings balance between ordered (ridged) structure and disordered structure
Mechanical support and flexibility
Dynamic interactions between membrane components
Membrane assembly and modification

Question 9

Why is cholesterol important in membrane fluidity

Answer 9

Alters packing and flexibility of lipids

Question 10

What are glycolipids and glycoproteins

Answer 10

Lipids and proteins with carbohydrates attached

Question 11

Composition of cell membranes can be changed by

Answer 11

Desaturation of lipids

Exchange of lipid chains

Question 12

What are lipid rafts

Answer 12

Small areas of the plasma membrane that are enriched in certain types of lipids like cholesterol

Question 13

Describe the properties of lipid rafts

Answer 13

Rafts are relatively ridged
Some membrane proteins accumulate in rafts
May form a functional compartment

Question 14

What can pass easily across a membrane

Answer 14

Small uncharged mollecules

Question 15

What cannot easily pass across the mebrane

Answer 15

Large /polar/ charged

Question 16

Name the 4 basic mechanisms for moving molecules across membranes

Answer 16

Simple diffusion
Diffusion through a channel
Facilitated diffusion
Active transport

Question 17

What passes by simple diffusion

Answer 17

Very small molecules
Uncharged
Sown a gradient
O2 CO2 H2O

Question 18

What passes by diffusion through a Chanel

Answer 18

Small charged molecules, ions
Down a gradient

Na+ K+ Ca+ Cl-

Question 19

What are ion channels formed by

Answer 19

Formed by integral membrane proteins that line in an aqueous pore

Question 20

What passes through an ion channel

Answer 20

Only one type of ion can pass
Down a conc gradient
Often are gated

Question 21

What are the 3 types of gated channels

Answer 21

Voltage gated channels
Ligand gated channels
Mechano gated channels

Question 22

What passes by facilitated diffusion

Answer 22

Compounds bind to integral membrane protein called a facilitative transporter and the change in conformation allows compound to be released on the other side of the membrane

Question 23

What active transport

Answer 23

Compunds binds specifically to integral membrane and change in conformation allows compound to be released on other side of membrane
Moves against a gradient

Question 24

What is a glycocalyx

Answer 24

An assembly of carbohydrate groups attached to proteins and lipids on the outside of the plasma membrane

Question 25

What is the purpose of a glycocalyx

Answer 25

Mediates cell cell and cell EMC interactions
Provides mechanical protection
Serves as a barrier to some particles
Binds regulatory factors

Question 26

What are the 6 functions of biological membranes

Answer 26

Cell boundary
Define/enclose compartments
Control movement of material into/out of the cell
Allows response to external stimuli
Enable interactions between cells
Provide scaffold for biochemical activities