Topic 4.1 Cell transport mechanisms

Question 1

What are the 3 main types of passive transport?

Answer 1

• diffusion
• facilitated diffusion
• osmosis

Question 2

Define passive transport

Answer 2

a transport that takes place as a result of concentration, pressure or electrochemical gradients and involves no energy from a cell

Question 3

Define active transport

Answer 3

the movement of substances into or out of a cell using ATP produced during cellular respiration

Question 4

Name the 3 active transport mechanisms

Answer 4

1) endocytosis
2) exocytosis
3) active transport

Question 5

Define diffusion

Answer 5

the movement of the particles in a liquid or gas down a concentration gradient from an area of high concentration to an area of low concentration

Question 6

Define facilitated diffusion

Answer 6

diffusion which takes place through carrier proteins or protein channels

Question 7

Define osmosis

Answer 7

the movement of solvent molecules down a concentration gradient

Question 8

Define endocytosis

Answer 8

the movements of large molecules into cells through vesicle formation, uses energy

Question 9

Define exocytosis`

Answer 9

the movement of large molecules out of the cell by fusing the vesicle with the cell surface membrane, requiring ATP

Question 10

What molecules are transported by facilitated diffusion?

Answer 10

• substances with strong positive or negative charges

- large molecules

Question 11

Define osmotic concentration

Answer 11

a measure of the concentration of solutes in a solution that have an osmotic effect

Question 12

What is an isotonic solution?

Answer 12

a solution in which the osmotic concentration of solutes is the same as that in the cells

Question 13

What is an hypertonic solution?

Answer 13

a solution in which the osmotic concentration of solutes is higher than that in the cell contents

Question 14

Define a hypotonic solution

Answer 14

a solution in which the osmotic concentration of the solutes is lower than that in the cell

Question 15

Define pressure potential

Answer 15

a measure of the inward pressure exerted by the plant cell wall on the protoplasm of the cell, opposing the entry of water by osmosis. usually has a positive value

Question 16

What is turgor?

Answer 16

the state of a plant cell when the solute potential causing the water to be moved into the cell by osmosis is balanced by the force of the cell wall pressing on the protoplasm

Question 17

Define incipient plasmolysis

Answer 17

the point at which so much water has moved out of the cell by osmosis that turgor is lost and the cell membrane begins to pull away from the cell wall as the protoplasm shrink

Question 18

What is plasmolysis?

Answer 18

the situation where a plant cell is placed in a hypertonic solution when so much water leaves the cell by osmosis that the vacuole is reduced and the protoplasm is concentrated and shrinks away from the cell wall

Question 19

Define water potential

Answer 19

a measure of the potential water has to move out of a cell by osmosis

Question 20

Define turgor pressure

Answer 20

a measure of the inward pressure exerted by the plant cell wall on the protoplasm of the cell as the cell contents expand and press outwards, a force which opposes the entry of water by osmosis

Question 21

What is osmotic potential?

Answer 21

a measure of the potential of a solution to cause water to move into the cell across a partially permeable membrane as a result of dissolved solutes

Question 22

Give the equation to determine water potential of a cell

Answer 22

water potential of cell= turgor pressure + osmotic potential

Question 23

Is the value of osmotic potential always positive or negative

Answer 23

always negative

Question 24

What happens when too much water enters an animal cell?

Answer 24

the cell bursts

Question 25

What happens when too much water leaves an animal cell?

Answer 25

the cell shrivels

Question 26

Which solution has the highest water potential?

Answer 26

pure water, value of 0

Question 27

Which solution has the highest osmotic potential?

Answer 27

pure water

Question 28

What is the trend in osmotic potential?

Answer 28

the greater the solute concentration of a solution, the lower/more negative the osmotic potential

Question 29

What are carrier proteins?

Answer 29

proteins that move a substance through the membrane in active transport

Question 30

What metabolic poison stops mitochondria from working?

Answer 30

cyanide

Question 31

Define phagoctosis

Answer 31

the active process when a cell engulfs something relatively large such as a bacterium and encloses it in a vesicle

Question 32

What is pinocytosis?

Answer 32

the active process by which cells take tiny amounts of extracellular fluid into vesicles

Question 33

State the evidence for active transport (4 reasons)

Answer 33

1) active transport only takes place in living, respiring cells
2) the rate of active transport depends on the temperature and oxygen concentration. affecting the rate of respiration and production of ATP
3) many cells known to carry out lots of active transport contain large numbers of mitochondria- site of aerobic respiration and ATP production
4) poisons that stop respiration or prevent ATPase also stop active transport. e.g. cyanide prevents synthesis of ATP during respiration and active transport. however, if ATP is artificially added, active transport starts again