Chapter 4

Question 1

what part of the phospholipid is hydrophilic

Answer 1

head so point to the outside

Question 2

what part of the phospholipid is hydrophobic

Answer 2

tail so point into the centre

Question 3

3 main functions of the phospholipid membrane

Answer 3

allow lipid-soluble substances to enter and leave the cell, prevent water-soluble substances entering and leaving, make the membrane flexible

Question 4

Two types of proteins found in the bilayer

Answer 4

mechanical proteins and channel proteins

Question 5

what is a mechanical protein

Answer 5

a protein that doesn’t extend along the whole width of the bilayer, they are there for support or are receptors

Question 6

what is a protein channel

Answer 6

water-filled tubes to allow water soluble ions to diffuse across

Question 7

what are carrier proteins

Answer 7

bind to ions or molecules like glucose which causes a change in shape allowing these to move across the membrane using energy from ATP

Question 8

6 functions of proteins in the bilayer

Answer 8

provide structural support, act as channels allowing water-soluble substances to cross, allow active transport across the membrane through carrier proteins, identification of cells, adhere cells together, receptors

Question 9

2 functions of cholesterol in the membrane

Answer 9

reduce movement of molecules, prevent the leakage of water and dissolved ions

Question 10

what is a glycolipid

Answer 10

made up of a carbohydrate covalently bonded with a lipid

Question 11

3 functions of glycolipids in the membrane

Answer 11

recognition, stability, help cells to attach to one another

Question 12

what is a glycoprotein

Answer 12

carbohydrate chain attached to extrinsic proteins

Question 13

2 functions of glycoproteins

Answer 13

recognition, help cells to attach

Question 14

3 types of molecule that cannot diffuse through the membrane

Answer 14

lipid-insoluble, too large, polar molecules

Question 15

what does fluid mean in fluid mosaic

Answer 15

the flexible structure that is constantly changing shape

Question 16

what does the mosaic mean in fluid mosaic

Answer 16

proteins are embedded and vary in shape, size, pattern

Question 17

simple diffusion definition

Answer 17

the net movement of particles from an area of high concentration to an area of low concentration down a concentration gradient until equilibrium has been reached

Question 18

facilitated diffusion definition

Answer 18

the net movement of particles from an area of high concentration to an area of low concentration down a concentration gradient through a transmembrane channel until equilibrium has been reached

Question 19

osmosis definition

Answer 19

the net movement of water from an area of higher water potential to an area of low water potential down a concentration gradient through a semi-permeable membrane

Question 20

active transport definition

Answer 20

the movement of molecules into or out of a cell from a region of low concentration to a region of higher concentration using ATP and carrier proteins

Question 21

how is glucose/ amino acids absorbed

Answer 21

sodium ions are actively transported out of epithelial cells into the blood via the sodium potassium pump. This maintains a higher concentration of sodium in the lumen compared to the epithelial cell. Sodium ions diffuse into the epithelial cell down a concentration gradient through a protein carrier. As the sodium diffuses in, there is space for the protein to carry either glucose or amino acid molecules into the cell with them, the glucose/ amino acids are passed into the blood from the epithelial cell via facilitated diffusion

Question 22

co-transport definition

Answer 22

Co-transport is the coupled movement of substances across a cell membrane via a carrier protein