4.1 structure of the cell surface membrane (DO EVERYDAY)

Question 1

function of phospholipids (3)

Answer 1

• 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 2

function of proteins (5)

Answer 2

• provide structural support
• help cells adhere
• act as receptors
• allow active transport through carrier proteins
• act as channels transporting water-soluble substances across the membrane

Question 3

function of cholesterol (3)

Answer 3

• reduce lateral movement of other molecule
• make the membrane less fluid at high temperature
• prevent leakage of water and dissolved ions from the cell

Question 4

function of glycolipids (3)

Answer 4

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

Question 5

function of glycoproteins (3)

Answer 5

• act as recognition sites
• help cells to attach to one another and so form tissues
• allow cells to recognize one another

Question 6

functions of membranes within cell (5)

Answer 6

• control the entry and exit of materials in discrete organelles
• separate organelles from cytoplasm so that specific metabolic reactions can take place within them
• provide an internal transport system
• isolate enzymes that might damage the cell
• provide surfaces on which reactions can occur

Question 7

why is the cell- surface membrane described as fluid?

Answer 7

molecules can move relative to one another

Question 8

why is the cell- surface membrane described as a mosaic?

Answer 8

proteins embedded vary in shape, size and pattern

Question 9

state properties of molecules that do not freely diffuse across the membrane

Answer 9

• not lipid soluble
• too large to pass the channels
• same charge as on the protein channel so is repelled
• polar so cannot pass non-polar hydrophobic tails

Question 10

what are glycoproteins made up of?

Answer 10

carbohydrate chains attached to extrinsic proteins

Question 11

what type of polarity does cholesterol have?

Answer 11

very hydrophobic

Question 12

how do phospholipids arrange themselves in the bilayer?

Answer 12

• hydrophilic heads point outside

- hydrophobic tails point inside

Question 13

what are protein channels?

Answer 13

water-filled tubes

Question 14

what do protein channels allow through?

Answer 14

allow water-soluble ions to diffuse across the membrane

Question 15

how do carrier proteins allow substances through?

Answer 15

• bind to ion

- change shape in order to move these molecules across the membrane