Structure of cell surface membrane

Question 1

what is plasma membrane

Answer 1

another name for cell-membrane and forms boundaries btwn cell cytoplasm & enviroment

Question 2

What is the purpose of cell-surface membrane

Answer 2

controls movement of substances in & out the cell

Question 3

what do phospholipids do

Answer 3

they form a bilayer

Question 4

which molecules can pass through the phospholipid bilayer

Answer 4

1. small molecules like O2 & CO2 because they are small
2. lipid soluble molecules can pass through the tails

Question 5

which molecules cannot pass through the phospholipid bilayer

Answer 5

1. big molecules such as Na+ cannot pass through as they are to big to pass through and cannot get through the fatty acid tails

Question 6

what are protein channels

Answer 6

these are channels that allow certain molecules to pass through
not open forever

Question 7

what type of molecules are allowed to pass through when protein channels are open

Answer 7

allow through water soluble ions to diffuse through

Question 8

what are carrier proteins

Answer 8

they change their shape to allow the entry of large & polar molecules to enter the cell

Question 9

what is the purpose of proteins in phospholipid bilayers

Answer 9

mechanical support to the membrane or in conjunction with glycoproteins as receptors on the surface

Question 10

what type of diffusion is used in protein channels & carrier proteins

Answer 10

passive diffusion

Question 11

what is passive transport

Answer 11

when energy is not required as the diffusion is not going against the gradient

Question 12

what is active transport

Answer 12

energy driven because its moving against a gradient

Question 13

what are the functions of proteins inside the membrane?

Answer 13

1. gives structural support
2. they allow active transport through carrier proteins
   3.cell-surface receptors
   4.act as channels transporting water soluble substances across the membrane

Question 14

what is the purpose of cholesterol inside the cell membrane

Answer 14

they add strength to the membrane and prevent water loss and the dissolving of ions from the cell as they are hydrophobic

Question 15

what is the function of cholestral in the membrane

Answer 15

1. the reduce lateral movement
   2.regulates the fluidity of the cell membrane
2. prevents cell membrane from becoming to fluid when temp. is high.
3. stops cell membrane from becoming rigid (frozen) when temp. is to low

Question 16

what is the phospholipid bilayer made of

Answer 16

hydrophilic heads
hydrophobic tails

Question 17

which way do the hydrophilic heads face and why

Answer 17

they face outwards to the cell membrane as they are hydrophilic (attracted to water)

Question 18

which way do hydrophobic tails face and why

Answer 18

the face inwards because they repel water.

Question 19

what is the functions of the phospholipids

Answer 19

1. to allow lipid soluble substances to enter & leave
2. prevent water soluble through & out
3. make membrane flexible self-sealing

Question 20

what is the arrangement fluid-mosaic model

Answer 20

this is the way all the various molecules are combined into the cell-surface menbmerna

Question 21

State through which molecule in the cell-surface membrane each of the following are likely to pass in order to get in or out of a cell.
a. a molecule that is soluble in lipids
b. a mineral ion

Answer 21

a. phospholipid
b. protein

Question 22

what are glycolipid made out of?

Answer 22

a carbohydrate covalently bonded with a lipid

Question 23

what is the function of glycolipid?

Answer 23

act as recognition sites
* help maintain the stability of the membrane * help cells to attach to one another and so form tissues

Question 24

what are glycoproteins

Answer 24

Carbohydrate chains are attached to many extrinsic proteins on the outer surface of the cell membrane

Question 25

what are the functions of glycoproteins

Answer 25

1. to act as recognition sites
2. helps cells attach to one another and form tissues
   3.allows cells to recognize on another