Transport (Diffusion, Active Transport, Osmosis)

Question 1

Diffusion

Answer 1

Diffusion is the net movement of particles from an area of high concentration to an area of lower concentration. It describes the movement of particles in fluids (liquids and gases). The particles all move randomly. Substances can move in and out of cells across cell membranes via diffusion (e.g CO2, urea).

Question 2

Diffusion Example

Answer 2

The random movement of particles through a gas or liquid from high concentration to a low concentration.

Question 3

Perfume

Answer 3

When you spray perfume, the smell diffuses across the room from the high concentration (where you just sprayed it) to low concentration (the other side of the room).

Answer 4

When you spray perfume, the smell diffuses across the room from the high concentration (where you just sprayed it) to low concentration (the other side of the room).

Question 5

Urea

Answer 5

a waste product of cells, diffuses out of cells and into the blood for excretion by the kidneys

Question 6

Which of the following is a waste product removed during diffusion?

Answer 6

CO₂

Question 7

Factors Affecting Diffusion

Answer 7

The rate of diffusion can speed up or slow down.

Question 8

Concentration gradient

Answer 8

The concentration gradient is linked to the difference in concentration between two areas.
The bigger the difference in concentration between two areas, the greater the concentration gradient and the faster the rate of diffusion.

Question 9

Membrane surface area

Answer 9

The larger the surface area of the membrane that a substance is diffusing through (e.g. the membrane around a cell), the faster the rate of diffusion.

Question 10

Temperature

Answer 10

The higher the temperature, the faster the rate of diffusion.

Question 11

Which of the following does NOT affect the rate of diffusion across membranes?

Answer 11

Colour of molecule

Question 12

Select the factors that will create the highest rate of diffusion

Answer 12

Large membrane surface area, high temperature and high concentration gradient

Question 13

The concentration gradient is the difference in concentration between two areas

Answer 13

The bigger the difference in concentration, the greater the concentration gradient and the faster the rate of diffusion.

Question 14

What would happen to the rate of diffusion if the concentration got steeper and the temperature rose?

Answer 14

The speed of diffusion would increase

Question 15

Osmosis

Answer 15

Osmosis is the diffusion of water across a partially permeable membrane from a dilute solution (high concentration of water) to a concentrated solution (low concentration of water).

Question 16

Partially permeable membrane

Answer 16

A partially permeable membrane allows water through, but won’t let larger molecules dissolved in water pass through.

Question 17

Water movement

Answer 17

Water will move to make the concentrations the same on both sides of the membrane:
When there are lots of water molecules (in a dilute solution) on one side of a partially permeable membrane, but not many on the other side (in a concentrated solution), water will move from the dilute to the concentrated solution.

Question 18

Net movement of water

Answer 18

It is important to remember that water molecules will move through the membrane in both directions, but the net (overall) movement of water will be from the dilute solution to a concentrated solution.

Question 19

Osmosis

Answer 19

Osmosis

Osmosis is the diffusion of water across a partially permeable membrane from a dilute solution (‘high concentration’ of water) to a concentrated solution (‘low concentration’ of water).

Question 20

Which of the following is a specialised plant tissue that uses osmosis to absorb water

Answer 20

Root hair cell

Question 21

Osmosis is the diffusion of water across a partially permeable membrane from a what solution?

Answer 21

Osmosis is the diffusion of water across a partially permeable membrane from a dilute solution (‘high concentration’ of water) to a concentrated solution (‘low concentration’ of water).

Question 22

Experiment definition

Answer 22

Experiment
An experiment is a test under controlled conditions. There are two main variables in an experiment - the independent variable and the dependent variable.

Question 23

Independent variable

Answer 23

This is the variable that you control - it is changed to see how the dependent variable will change. For example, in an osmosis experiment, you change the concentration of the sugar solution each time. This is the independent variable.

Question 24

Dependent variable

Answer 24

The dependent variable is the variable that you measure as an outcome of the experiment. In the osmosis experiment, it will be the change in the mass of the object being used.

Question 25

Investigating Osmosis

Answer 25

This experiment shows the effect of water concentration on osmosis.

Question 26

Measure change in mass

Answer 26

Cut discs of raw potato and measure their mass. Put discs in different concentrations of sugar or salt solution. After 30 minutes, measure the mass of each disc again.

Question 27

Calculate percentage change in mass

Answer 27

Subtract the final mass from the initial mass of each disc. Divide this number by the initial mass and then multiply by 100 to give a percentage change in mass. The concentration in which the potato's mass changed the least is closest to the water concentration of the potato (because the least water has moved into or out of the potato by osmosis).

Question 28

Disc mass

Answer 28

Disc mass By measuring the mass of each disc before and after being put in solution, the change in mass can be worked out; the mass of a disc may have increased, decreased or stayed the same.

Question 29

Decreased

Answer 29

If the mass of a disc decreased, it has lost water by osmosis.

Question 30

Stayed the same

Answer 30

Stayed the same If the disc's mass did not change, it has neither gained nor lost water by osmosis.

Question 31

Increased

Answer 31

If the mass of the disc increased, it has gained water by osmosis.

Question 32

Lost

Answer 32

Water moved out of the potato cells by osmosis because the water concentration of the solution was lower than that of the cells.

Question 33

Neither

Answer 33

Water did not move into or out of the potato cells because the water concentration of the solution was equal to that of the cells.

Question 34

Gained

Answer 34

Water moved into the potato cells by osmosis because the water concentration of the solution was higher than that of the cells.

Question 35

Active Transport in Humans and Plants: Sugar absorption in human gut

Answer 35

Active transport allows sugar molecules, which are needed for cell respiration, to be absorbed into the blood from the gut, even when the sugar concentration of the blood is higher.

Question 36

Active transport allows sugar molecules, which are needed for cell respiration, to be absorbed into the blood from the gut, even when the sugar concentration of the blood is higher.

Answer 36

Active transport in the root hairs of plants allows plants to absorb mineral ions, which are necessary for healthy growth, even though the concentration of minerals is usually lower in the soil than in the root hair.

Question 37

In active transport, molecules are transported from

Answer 37

a low concentration to a high concentration.

Question 38

Active transport is the process where dissolved molecules move from

Answer 38

a less concentrated solution to a more concentrated solution. As the net movement of molecules is against the concentration gradient, energy is required. This energy is provided by respiration.

Question 39

Name the substances that are absorbed via active transport in the following structures:

Answer 39

Minerals: Roots of plants Sugar: Guts of humans

Question 40

Transport in Cells The three main forms of transport in cells are: Diffusion

Answer 40

Diffusion is the net movement of particles from an area of high concentration to an area of lower concentration.

Question 41

Osmosis

Answer 41

Osmosis is a special case of diffusion where only water molecules move. It requires a partially permeable membrane

Question 42

Active transport

Answer 42

Active transport is the net movement of particles against a concentration gradient. Energy is therefore required.

Question 43

Select the processes that are forms of passive transport?

Answer 43

Osmosis, diffusion

Question 44

Blackcurrant Squash - Diffusion or Osmosis? The example of blackcurrant squash being added to water can be used to demonstrate the difference between osmosis and diffusion.

Answer 44

Diffusion When you add blackcurrant squash to water, the particles in squash spread out, so that the strength of its flavour is the same throughout the whole drink. The squash molecules move from the high concentration of squash molecules to the low concentration. This is diffusion, not osmosis.

Question 45

Osmosis

Answer 45

Osmosis Osmosis would take place if the orange squash was trapped inside a membrane. The water moves instead of the squash molecules. To equalise the concentration, the water moves into the membrane: The water moves from the dilute solution (outside the membrane) to the concentrated solution (where the squash is).

Question 46

Pair the following definitions with a method of transportation in cells:

Answer 46

Diffusion This is the net movement of particles from an area of high concentration to an area of lower concentration. This is a form of passive transport (which does not require any energy). Active transport This is the net movement of particles against a concentration gradient, and so energy is required. Osmosis This is a special case of diffusion, where only water molecules move. It requires a partially permeable membrane. This is a form of passive transport (which does not require any energy).

Question 47

Complete the following sentences about forms of transport in cells:

Answer 47

Diffusion is the net movement of particles from an area of high concentration to an area of low concentration. Osmosis is a special case of diffusion where only water molecules move. It requires a partially permeable membrane. Active transport is the net movement of particles against a concentration gradient. Energy is therefore required.