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Flashcards in Movement Into And Out Of Cells Deck (15):
1

Define diffusion

The net movement of particles from an area of high concentration to an area of low concentration down a concentration gradient.

2

Give three examples of diffusion

Oxygen exiting the alveoli and carbon dioxide entering them
Digested food diffusing into the villi
The placenta

3

State the living diffusion experiment.
What is the problem with it?

Put cubes of beetroot into five different boiling tubes.
Fill each tube with water of different temperatures.
The pigment in the beetroot should diffuse out into the water.
The test tube with the highest temperature should attain the fastest rate of diffusion.

The problem is that it really shows cell permeability instead of how temperature affects diffusion rate.

4

State the non-living diffusion experiment

Fill a beaker with water and pink dye.
Put cubes of agar jelly in.
The dye should diffuse into the jelly.
See and measure the time it takes for the jelly to become completely pink (dye fully diffused).

5

Define osmosis

The net movement of water molecules from an area of high water potential to an area of low water potential across a semipermeable membrane down a water potential gradient.

6

Give an example of osmosis

Water molecules in the soil entering a root hair cell.

7

Describe and explain osmosis in animals cells

If the cytoplasm of animal cells, such as red blood cells, has a lower water potential than its surroundings then water will move into the cells by osmosis and they will swell and burst (hypotonic).
If the cytoplasm of the cell has a higher water potential than its surroundings then water will leave the cell by osmosis and the cell will shrivel up (hypertonic).
If the water potential is equal inside the cell and outside the cell, it will remain normal (isotonic).

8

Describe and explain osmosis in plant cells

Unlike animals cells, plants have a cell wall, which means that when water enters the plant cell by osmosis (because the water potential in the cytoplasm is lower than that of its surroundings), the vacuole swells up and pushes against the wall but doesn’t burst. It becomes turgid.
When the water leaves plant cells by osmosis because the water potential within the cytoplasm is higher than that of its surroundings, the vacuole shrinks and the cell membrane begins to pull away and peel off the cell wall (plasmolysis). The cell is flaccid.

9

State the non-living experiment for osmosis

Put pure water into a beaker.
Put a highly concentrated sucrose solution into a visking tube.
Because the water potential is higher in the beaker than in the tube, the water should enter the tube (as it is a semipermeable membrane), making the liquid within it rise up into the capillary tube. Sucrose molecules, however, cannot cross the membrane and into the beaker as they are too big.
Repeat with different concentrations.

10

State the living experiment for osmosis

Cut out equal-sized cylinders of potato.
Bolt them with tissue paper.
Weigh each of them and modify so that they all have the same volume, surface area and mass.
Put each cylinder into test tubes with different sucrose concentrations for a few hours.
Remove them, blot them with tissue paper, and re-weigh them.
In pure water (very low sucrose concentration), water enters the potato cells by osmosis as the surroundings have a higher water potential than the cytoplasm of the cells. The potato should swell up and gain weight.
In very high sucrose concentrations, water exits the cells by osmosis as the surroundings have a lower water potential than the cytoplasm of the cells. The potato shrinks and loses weight.

The lower the concentration of sucrose, the higher the percentage change in mass.

11

What is the equation for percentage change in mass?

Percentage change in mass = ((end mass - start mass)/start mass) x 100

12

Define active transport

He movement of particles from an area of low concentration to an area of high concentration against a concentration gradient, using up energy in the form of ATP. This requires a transporter protein.

13

Give an example of active transport

Mineral ions in the soil entering a root hair cell.

14

What are mineral ions required for in plants?

Nitrates- provide a source of the element nitrogen which is used to make amino acids which join together to make proteins. Needed for growth.

Magnesium- required to make chlorophyll.

15

What are the factors affecting movement in and out of cells?

Distance- as the distance increases, the rate of diffusion decreases as the molecules have further to travel.
Temperature- as the temperature increases, the rate increases as the molecules have more kinetic energy and are therefore able to move faster.
Concentration gradient- the steeper the concentration gradient, the faster the rate of movement of molecules.
Surface area to volume ratio- the larger the ratio, the greater the surface area over which the movement of molecules can take place.