cell membranes

Question 1

list three functions of cell membranes

Answer 1

• cell recognition
• control of transport of substances
• contains organelles

Question 2

what is the name of the arrangement of cell membrane?

Answer 2

fluid-mosaic model

Question 3

why is it described as a fluid-mosaic model?

Answer 3

fluid- individual phospholipid molecules can move relative to one another so membrane is flexible and can change shape
mosaic - scattered proteins embedded in bilayer varies pattern, shape and size like a mosaic

Question 4

name five molecules in a cell membrane

Answer 4

• phospholipid
• cholesterol
• glycolipid
• protein
• glycoprotein
• cholesterol

Question 5

what type of layer do the phospholipids form?

Answer 5

bilayer

Question 6

describe structure of bilayer

Answer 6

• hydrophilic head point out - attracted to water

- hydrophobic head points in - repelled by water

Question 7

what are the functions of the phospholipids?

Answer 7

• make membrane flexible
• allow entry/exit of lipid-soluble substances
• prevent entry/exit of water-soluble substances

Question 8

what are the two types of protein in membrane?

Answer 8

• intrinsic

- extrinsic

Question 9

name two types of intrinsic proteins

Answer 9

• channel proteins

- carrier proteins

Question 10

how does a channel protein work?

Answer 10

facilitated diffusion - forms a water-filled hydrophilic channel across membrane
- charged particles diffuse down gradient

Question 11

how do carrier proteins work?

Answer 11

facilitated diffusion - large molecules attached to membrane and protein changes shape so then it releases the molecule on opposite side of membrane

Question 12

functions of proteins in membrane

Answer 12

• structural support
• act as channels
• allow active transport/ facilitated diffusion through carrier proteins
• helps cells adhere together
• act as receptors

Question 13

where are glycoproteins attach on membrane?

Answer 13

carbohydrate chain attached to extrinsic proteins

Question 14

functions of glycoprotein

Answer 14

• cell recognition
• cell receptors - hormones/ neurotransmitters
• help cells attach and form tissues

Question 15

what is a glycolipid made of?

Answer 15

a carbohydrate covalently bonded to a lipid

Question 16

where are glycolipids in membrane?

Answer 16

extends from bilayer into water environment

Question 17

functions of glycolipid

Answer 17

• cell receptor (ABO blood)
• cell recognition
• stability of membrane
• help cells attach and form tissues

Question 18

how does cholesterol affect the movement of molecules in cell membrane?

Answer 18

restricts movement because it pulls together fatty acid tails

Question 19

other functions of cholesterol

Answer 19

• reduces lateral movement of phospholipids
• prevents leakage of water and dissolved ions from cell because it is hydrophobic
• makes membrane less fluid at high temperatures

Question 20

name three factors that affect the permeability of membranes

Answer 20

• pH
• solvent
• temperature

Question 21

how does pH affect the permeability of membranes?

Answer 21

• low pH - proteins are denatured due to interference of hydrogen bonding
• holes are formed so molecules pass through by diffusion and disrupts mosaic pattern

Question 22

how do solvents affect the permeability of membranes?

Answer 22

higher concentration of solvent the more permeable

• ethanol dissolves phospholipids due to polar/non-polar ends
• it affects fluidity of membrane by denaturing function of embedded proteins
• mosaic falls apart so molecules easily diffuse through

Question 23

how does temperature affect the permeability of membranes?

Answer 23

• at high temp, molecules vibrate faster and water expands putting pressure on membrane
• lipids more fluid so membranes are fragile
• proteins denature because vibrations disrupt hydrogen bonding
• membrane will have gaps for molecules to diffuse through