transport in cells

Question 1

define diffusion

Answer 1

the net movement of molecules or ions from an area of high concentration to an area of low concentration

Question 2

what factors affect the rate of diffusion?

Answer 2

• concentration gradient
• increased surface area
• increased temperature
• decreased diffusion distance

Question 3

what is diffusion always affected by?

Answer 3

> the size and nature of diffusing molecules
- smaller molecules are faster than larger molecules
- lipid soluble are faster than water soluble
- non polar are faster than polar
- ions can’t diffuse across a membrane

Question 4

what is facilitated diffusion?

Answer 4

• it requires a protein molecule in the cell membrane (carrier or channel) to transport polar molecules and water soluble molecules across the membrane

Question 5

define osmosis

Answer 5

the diffusion of water molecules from an area of high water potential to an area of low water potential though a partially permeable membrane

Question 6

what is active transport?

Answer 6

the transport of molecules through carrier proteins from an area of low concentration to an area of high concentration - requires energy from in the form of ATP

Question 7

what’s the role of exocytosis?

Answer 7

• transports large molecules
• the vesicles containing large particles are fused with the cell membrane and released from the cell

Question 8

what’s the role of endocytosis?

Answer 8

• transports large molecules
• the particles are enclosed in vesicles made from the cell membrane and are transported into the cell in endocytosis

Question 9

what is co-transport?

Answer 9

uses ions (sodium and potassium ions) to move substances in and out of cells

Question 10

define osmosis

Answer 10

the passage of water from a region of a high water potential to low water potential across a partially permeable membrane

Question 11

what is the water potential of pure water?

Answer 11

0

Question 12

what is the net movement of water when a cell is placed in a hypotonic solution?

Answer 12

water moves into the cell by osmosis

Question 13

what is the net movement of water when a cell is placed in an isotonic solution?

Answer 13

there is no net movement

Question 14

what is the net movement of water when a cell is placed in hypertonic solution?

Answer 14

water moves out of the cell by osmosis

Question 15

what would happen if an animal cell is placed in a hypotonic or hypertonic solution?

Answer 15

hypotonic - cell is haemolysed
hypertonic - cell is crenated

Question 16

what would happen if a plant cell is placed in a hypotonic, isotonic or hypertonic solution?

Answer 16

hypotonic - cell is turgid
isotonic - cell is flaccid
hypertonic - cell is plasmolysed

Question 17

what is a hypotonic solution?

Answer 17

‘hypo’ means ‘less’
- there is a lower concentration of solutes than inside the cell cytoplasm
- higher water potential outside the cell

Question 18

what is an isotonic solution?

Answer 18

‘iso’ means ‘same’
- it’s the same concentration of solutes inside and outside the cell
- same water potential inside & outside the cell

Question 19

what is a hypertonic solution?

Answer 19

‘hyper’ means ‘more’
- there is a greater concentration of solutes than inside the cell cytoplasm
- lower water potential outside the cell

Question 20

describe co-transport in the small intestine

Answer 20

• sodium is actively pumped out of intestinal cells (via active transport)
• sodium and glucose move into intestinal cell by facilitated diffusion using carrier proteins
• glucose diffuses into the blood by facilitated diffusion using channel proteins