plasma membranes (7)

Question 1

what are phospholipis?

Answer 1

Lipids with a phosphate group (PO42-) covalently bonded to the glycerol backbone instead of a fatty acid

Question 2

in water what do phospholipids form ?

Answer 2

a bilayer

Question 3

how do people often describe the structure of the phospholipid bilayer ?

Answer 3

the fluid mosaic model

Question 4

what is the width of the bilayer ?

Answer 4

very thin membrane (7-8nm

Question 5

why is the bilayer aften refered to as the fluid mosaic model ?

Answer 5

FLUID-a two-dimensional liquid that restricts the lateral diffusion of membrane components

MOSAIC-Regions within the membrane that contain lipid rafts, proteins and/or glycoproteins.

Question 6

What is the cell membrane comprised of ?

and in what quantity ?

Answer 6

• Phospholipids (75%)
• Cholesterol (20%)
• Polar Glycolipids in the external layer (5%)

Question 7

what is cholesterol ?
function in membrane ?

Answer 7

is a steroid lipid made up of ringed carbon structure with floppy carbon chain and hydrophilic hydroxyl (OH) group.

Useful structural lipid for membranes

Question 8

how does cholesterol stabalise the cell membrane ?

Answer 8

Cholesterol immobilises the first few hydrocarbon groups of the phospholipids molecules.
This makes the lipid bilayer less deformable and decreases its permeability to small water-soluble molecules.

Question 9

why is fluidity of the cell membrane important ?

Answer 9

Fluidity allows the movement of membrane components required for cell movement, growth, division, secretion and the formation of cellular junctions

Question 10

what is a glycolipid ?

Answer 10

Lipid covalently attached to an oligosaccharide

Question 11

name two functions of glycolipids

Answer 11

Forms part of cell membrane and glycocalyx

Determines ABO blood group

Question 12

what are 3 functions of the glycocalyx ?

Answer 12

Required for detection of ‘self’ in immunity
Aids in cell- cell adhesion
Makes RBCs slippery and protects the GI from drying out

Question 13

name 5 functions of the phospholipid bilayer

Answer 13

It regulates what enters and exits the cell (altering pH and charge)
Is involved with cell recognition
Plays a major role in cell signalling e.g. from hormones
Has enzymatic functions
Aids in cell linking and cross-talk

Question 14

as the lipid bilayer is semi perimeable name three substances that can pass the membrane

Answer 14

O2
CO2
Hormones

Question 15

what types of compounds ca pass the membrane ?

Answer 15

non-polar

small molecules

Question 16

how can impermeable substances pass the membrane ?

name two of these cant diffuse across

Answer 16

need trans-membrane channel and carrier proteins

Na+ and glucose.

Question 17

name a molecule in which the membrane is only slightly permeable

Answer 17

slightly polar molecules such as water (H20)

Question 18

Why is the fact that cell membranes are selectivly permeable imporntant ?

Answer 18

Selective permeability allows cells to build concentration gradients

Question 19

name two compunds that are more concentrated in the extracellular fluid

Answer 19

O2 and Na+

Question 20

name two compunds that are more concentrated in the intracellular fluid

Answer 20

K+ & CO2

Question 21

how is the electrical graient balenced ?

hint ;which is + or -

Answer 21

the inside of a cell is more –ve

Question 22

name three ways that substances move down the cocentration gradient across the cell membrane

Answer 22

– 1. Diffusion through lipid bilayer
– 2. Channel mediated facilitated diffusion
– 3. Carrier mediated facilitated diffusion

Question 23

how can channel mediated transport be controlled ?

Answer 23

Can be gated

Can be timed or signal regulated

Question 24

how can Carrier mediated transport be controlled ?

Answer 24

Subject to transport maximum and saturation

Question 25

how does the hormone insulin help to maintain homeostasis ?

Answer 25

, up-regulates (creates more hence making the cell more sensitive to) glucose transporters

Question 26

what are the transmembrane protein channels called that water diffuses through to pass the cell membrane ?

Answer 26

aquaporins

Question 27

define hypertonic

Answer 27

having a higher osmotic pressure than a particular fluid

Question 28

define isotonic

Answer 28

a solution having the same osmotic pressure as some other solution,

Question 29

define hypotonic

Answer 29

having a lower osmotic pressure than a particular fluid,

Question 30

what are isotonic solutions often ?

hint- in terms of saline or dextrose %

Answer 30

0.9% saline
or
5% dextrose

Question 31

how is actice transport different from its passive conterpart ?

Answer 31

Involves expenditure of energy from hydrolysis of ATP.

• It is used to transport essential ions against their concentration gradient

Question 32

what is the difference between primary and secondary active transport ?

Answer 32

Primary active transport (uses energy from the hydrolysis of ATP)
– Secondary active transport (uses energy stored by an ionic concentration gradient)

Question 33

what perecentage of a cells ATP do they use on active transport ?

Answer 33

40%

Question 34

descibe the sodium-potassium pump ?

Answer 34

3Na+ bind
ATP is hydrolysed (ATPase)
phosphate binds to protein carrier (leading to change in shape )
2K+ bind 
phosphate released (shape reverted back)
2K+ enters