cell membranes

Question 1

what are the main functions of plasma membranes

Answer 1

• forms a boundary between 2 environments (compartmentalisation) - this allows different conditions either sides of the membrane= different reactions
• a partially permeable barrier- controls the movement of substances in & out

Question 2

what are phospholipids made up of

Answer 2

• phosphate head (polar)
• glycerol
• hydrophobic tail
• fatty acids (non-polar)

Question 3

are phospholipid hydrophilic heads water soluble?

Answer 3

yes

Question 4

are phospholipid tails water soluble

Answer 4

no- they are water insoluble (hydrophobic)

Question 5

where are proteins in the cell membrane

Answer 5

randomly dotted throughout the cell surface membrane (embedded in the phospholipid layer)

Question 6

what are the 2 types of proteins?

Answer 6

1. extrinsic- found on surface of one side of the membrane
2. intrinsic- completely span the bilayer from one side to another

Question 7

what are the functions of membrane proteins?

Answer 7

• provide structural support
• act as receptors for molecules & identifying cells
• enzymes
• act as channel & carrier proteins

Question 8

what is a glycolipid

Answer 8

a carbohydrate chain attached to a lipid in the membrane

Question 9

what is a glycoprotein?

Answer 9

a carbohydrate chain attached to a protein
this carbohydrate part extends into the aqueoes environment outside the cell.

Question 10

what does a channel protein do? (intrinsic protein)

Answer 10

allows water soluble solutes to pass through the membrane

Question 11

what does a carrier protein do? (extrinsic protein)

Answer 11

change shape to what should/shouldnt transport through the membrane

Question 12

what are the overall functions of glycolipids and glycoproteins?

Answer 12

• provide stability
• act as cell-surface receptors for binding of molecules or recognition sites
• help cells attach to eachother (to form tissues)

Question 13

what are cholesterol?

Answer 13

• molecules found within the bilayer
• (ALWAYS in a chain of 4)
• e.g. steroid
• has a polar head group (OH) which can associate with heads of the phospholipids & surrounding aqeous environment

Question 14

functions of cholesterol

Answer 14

• adds strength and rigidity to the membrane
• preventing the loss of water and dissolved ions from cells

Question 15

permeable meaning

Answer 15

allows things to pass through it

Question 16

selective meaning

Answer 16

only permeable to certain things

Question 17

what can/can’t pass the phospholipid layer?

Answer 17

CAN- allows nonpolar substances to pass through & small molecules e.g. H2O

CAN’T- prevents most water soluble (polar) substances passing through.