Structure If The Cell Surface Membrane

Question 1

what is the plasma membrane?

Answer 1

-all members around and within all cells have that same basic structure

Question 2

what is a cell surface plasma membrane?

Answer 2

-the name given to the plasma membrane that surrounds cells and forms the boundary between the cell cytoplasm and the environment allowing different conditions to be established inside and outside of the cell

Question 3

what are phospholipids?

Answer 3

-they are important components of the cell surface membrane

Question 4

Why are phospholipids important?

Answer 4

• the hydrophilic heads of both phospholipid layers point to the outside of the cell surface membrane attracted by water on both sides
• the hydrophobic tails of both phospholipid layers point to the centre of the cell membrane repelled by the water on both sides

Question 5

What moves through the membrane via phospholipid portion?

Answer 5

-lipid soluble material

Question 6

what is the function of phospholipids in the membrane?

Answer 6

• allow lipid soluble substances to enter and leave the cell
• prevent water soluble substances entering and leaving the cell
• make the membrane flexible and self sealing

Question 7

where are proteins found in the phospholipid bilayer?

Answer 7

-proteins are interspersed throughout the cell surface membrane and embedded in the phospholipid bilayer as cell receptors, protein channels or carrier proteins

Question 8

what are extrinsic proteins?

Answer 8

• proteins that occur in the surface D the bilayer and never extend completely across
• they act to give mechanical support to the membrane or work with glycolipids as cell receptors for molecules like hormones

Question 9

what are channel proteins?

Answer 9

• they span the phospholipid bilayer from one side to the other
• they form water filled tubes to allow water soluble ions to diffuse across the membrane

Question 10

what are carrier proteins?

Answer 10

• they span the phospholipid bilayer from one side to the other
• they bind to ions or molecule like glucose then change shape in order to move these molecules across the membrane

Question 11

what are the functions of proteins in the membrane?

Answer 11

• they provide structural support
• act as channels transporting water so blunt substances across the membrane
• allow active transport across the membrane through carrier proteins
• form cell surface receptor se for identifying cells
• helps cells adhere together
• act as receptors

Question 12

what is cholesterol?

Answer 12

-cholesterol molecules occur within the phospholipid bilayer of the cell surface membrane

Question 13

what is the function of cholesterol in the membrane?

Answer 13

• reduce lateral movement of other molecules like phospholipids
• make the membrane less fluid at high temperatures
• prevents leakage of water and dissolved ions from the cell

Question 14

what are glycolipids made from?

Answer 14

• a carbohydrate covalent bonded with a lipid
• the carbohydrate portion extends from the phospholipid bilayer into the watery environment outside the cell where it acts as a cell surface receptor for specific chemicals

Question 15

what are the functions of glycolipids in the membrane?

Answer 15

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

Question 16

what are glycoproteins?

Answer 16

• carbohydrate chains that are attached to many extrinsic proteins on the outer surface of the cell membrane
• they act as cell surface receptors from hormones and neurotransmitters

Question 17

what are the functions of glycoproteins?

Answer 17

• act as recognition sites
• helps cells to attach to one another and so form tissues
• allows cells to recognise one another like lymphocytes can recognise own cells

Question 18

What does the cell surface membrane do?

Answer 18

-controls the movement of substances into and out of the cell

Question 19

Which molecules can’t diffuse freely across the cell surface membrane?

Answer 19

• molecules that aren’t soluble in lipids
• large molecules that can’t pass through the channels in the membrane
• molecules of the same charge as the protein channels are repelled
• electrically charged Polar molecules can’t pass through the non polar tails of the bilayer

Question 20

what is the fluid mosaic model?

Answer 20

-the way in which all the various molecules are combined into the structure of the cell surface membrane

Question 21

how is the fluid mosaic model fluid?

Answer 21

-the individual phospholipid molecules can move relative to one another which gives the membrane a flexible structure that is constantly changing shape

Question 22

how is the fluid mosaic model a mosaic?

Answer 22

-the proteins are embedded in the phospholipid bilayer vary in shape size and pattern in the same way as the stones or tiles of a mosaic

Question 23

What do cholesterol molecules do?

Answer 23

• they add strength to the membranes
• they are very hydrophobic so prevent loss of water and dissolved ions from the cell
• they pull together the fatty acid tails of the phospholipid molecules which limits their movement and that of other molecules without making the membrane too ridged