Cell Transport

Question 1

Ways substances can be transported across the cell membrane (5)

Answer 1

Diffusion, facilitated diffusion, osmosis, active transport, vesicular transport

Question 2

Diffusion

Answer 2

Passive transport, Movement of particles from an area of high concentration to low concentration, continues until equilibrium is reached

Question 3

Diffusion can occur

Answer 3

Across the phosphlipid layer of the cell membrane (lipid soluble substances), across the membrane via channel proteins (water and water soluble substances), across the membrane via carrier proteins (large molecules)

Question 4

Facilitated diffusion

Answer 4

Molecule (glucose or amino acid) travels through protein channel or binds to carrier protein

Question 5

Osmosis

Answer 5

Paasive, movement of water molecules across a semi-permeable membrane, moves until equilibrium is reached

Question 6

Hypotonic solution

Answer 6

Solute concentration in the solution is lower than in the cell, water will move into the cell causing it to lyse/swell or burst

Question 7

Isotonic solution

Answer 7

Same concentration of solute inside snd outside the cell

Question 8

Hypertonic solution

Answer 8

Solute concentration in the solution is higher than inside the cell, water will move out of the cell causing it to shrink/shrivel

Question 9

Factors that affect diffusion (6)

Answer 9

Molecule size, molecule shape, concentration, charge, lipid solubility, temperature

Question 10

How does molecule size affect diffusion

Answer 10

Small molecules such as oxygen and carbon dioxide can slip by the polar heads of the phospholipids to the other side, large molecules cannot diffuse across the membrane

Question 11

How does molecule shape affect diffusion

Answer 11

Means carrier proteins have to be used

Question 12

How does concentration affect diffusion

Answer 12

The greater the concentration gradient between the outside or inside of the membrane the greater the rate of diffusion, if concentration of oxygen outside the cell increases then it will diffuse more quickly into the cell

Question 13

How does molecule charge affect diffusion

Answer 13

Ions or molecules with a charge can’t pass through the lipid bilayer using diffusion, protein channels or carrier proteins are required

Question 14

How does lipid solubility affect diffusion

Answer 14

Lipid soluble molecules such as testosterone and oestrogen can move through the lipid bilayer

Question 15

How does temperature affect diffusion

Answer 15

Increases in temperature causes all molecules to move faster, quicker molecule movement translates into quicker diffusion

Question 16

The greater the surface area

Answer 16

The larger the amount of raw materials that can enter at any one time

Question 17

Active transport

Answer 17

Requires energy, Movement of particles across a semi-permeable membrane against the concentration gradient (low to high)

Question 18

Active transport occurs

Answer 18

So a concentration difference can be maintained or increased across a membrane, occurs via carrier proteins or vesicles

Question 19

Carrier proteins in active transport

Answer 19

Molecule binds to the carrier protein, ATP also binds to the carrier protein, energy is released to change the shape of the protein, molecule is released on the other side of the CM

Question 20

Endocytosis

Answer 20

Small pieces of membrane form vesicles sureounding material moving into the cell, the CM folds around the substance to enclose it, it pinches off and enters the cell

Question 21

Exocytosis

Answer 21

Small pieces of membrane form vesicles surrounding material moving out of the cell, moves to the CM, fuses with it and is pushed out of the cell