Unit 2 - Diffusion/osmosis/active transport

Question 1

Define diffusion

Answer 1

The net movement of particles from an region of higher concentration to a region of lower concentration

Question 2

Is diffusion active or passive?

Answer 2

Passive

Question 3

Define passive transport

Answer 3

Movement of substances that does not require energy

Question 4

Define osmosis

Answer 4

The movement of water from a region of high water potential to a region of low water potential across a partially permeable membrane

Question 5

Define facilitated diffusion

Answer 5

Diffusion across a plasma membrane through protein channels

Question 6

Is facilitated diffusion passive?

Answer 6

Yes

Question 7

Is osmosis passive or active?

Answer 7

Passive

Question 8

Define active transport

Answer 8

The movement of molecules from an area of low concentration of that molecule to an area of high concentration of that molecule. This movement requires ATP

Question 9

What sort of molecules tend to move via diffusion across a membrane?

Answer 9

-small molecules (e.g. gases)
-lipid soluble molecules
-non-polar molecules

Question 10

Which 2 factors affect the rate of diffusion?

Answer 10

Temperature
Concentration difference

Question 11

What effect does an increase in temperature have on the rate of diffusion?

Answer 11

It increases the rate of diffusion

Question 12

What effect does a greater difference in concentration of two regions have on the rate of diffusion?

Answer 12

It increases the rate of diffusion

Question 13

Why does a higher temperature increase rate of diffusion?

Answer 13

-higher temperature means particles have more kinetic energy and move at higher speeds

Question 14

Why is it easier for oxygen to diffuse across a membrane than water?

Answer 14

-oxygen molecules are small and non-polar whereas water molecules are polar
-the hydrophobic interior of the phospholipid bilayer repels the charged molecules
-water is only partially charged so is still able to diffuse through the membrane, though only slowly

Question 15

What 4 factors affect the rate of diffusion across a membrane?

Answer 15

-temperature
-concentration gradient
-surface area
-thickness of membrane

Question 16

Why are membranes containing protein channels selectively permeable?

Answer 16

-Most protein channels are specific to one molecule or ion
-Therefore only these specific molecules/ions are able to move across the membrane

Question 17

What does facilitated diffusion allow to move across a membrane?

Answer 17

-larger molecules
-lipid insoluble molecules
-small charged particles

Question 18

What does active transport require to occur?

Answer 18

ATP
Carrier proteins

Question 19

Define endocytosis

Answer 19

the bulk transport of material into cells

Question 20

Define pinocytosis

Answer 20

the bulk transport of liquids into cells

Question 21

Define phagocytosis

Answer 21

the bulk transport of solids into cells, most commonly the process by which white blood cells engulf pathogens

Question 22

Define exocytosis

Answer 22

the bulk transport of materials out of a cell

Question 23

Does bulk transport require ATP?

Answer 23

Yes

Question 24

Why would a molecule be moved by bulk transport?

Answer 24

It is too big for channel or carrier proteins

Question 25

Outline how exocytosis occurs

Answer 25

-vesicles are usually formed by the golgi apparatus
-vesicles move towards and fuse with the cell surface membrane
-contents of the vesicle are then released outside of a cell

Question 26

How can the effect of surface area on the rate of diffusion be investigated?

Answer 26

-agar made with phenolpthalein and NaOH is pink as NaOH is alkai
-cubes of different sizes are placed in HCl
-In HCl the cubes will go colourless
-Leave for 5 minutes
-measure the volume of cube that is still pink
-calculate % diffusion

Question 27

How can the effect of temperature on the rate of diffusion be investigated?

Answer 27

-an artificial cell is made from dialysis tubing
-solution is placed in cell
-cell is placed in water bath at different temperatures
-indicators can be used to see the rate of diffusion (e.g. iodine for starch or benedict’s solution for glucose)

Question 28

What is the effect of a higher surface area to volume ratio on the rate of diffusion?

Answer 28

It increases the rate of diffusion

Question 29

What is a hypertonic solution?

Answer 29

having a higher concentration of solute relative to another solution

Question 30

What is an isotonic solution?

Answer 30

having the same concentration of solute relative to another solution

Question 31

What is a hypotonic solution?

Answer 31

having a lower concentration of solute relative to another solution

Question 32

What would be the effect of placing a red blood cell in a hypotonic solution?

Answer 32

-net movement of water into the cell
-cell swells and bursts
-causing haemolysis
-cell contents lost, haemoglobin released

Question 33

What would be the effect of placing a red blood cell in a hypertonic solution?

Answer 33

-net movement of water out of the cell
-cell shrinks and shrivels
-becomes darker in colour as haemoglobin is more concentrated
-crenation

Question 34

What would be the effect of placing a plant cell in a hypotonic solution?

Answer 34

-net movement of water into cell
-cell becomes turgid
-protoplast pushed against cell wall

Question 35

What would be the effect of placing a plant cell in a hypertonic solution?

Answer 35

-net movement of water out of cell
-contents shrink
-cell plasmolysed
-protoplast completely pulled away