B2.1.1 - B2.1.3 - Supplying The Cell

Question 1

What is diffusion?

Answer 1

It is the passive net (overall) movement of particles from an area of high concentration to an area of low concentration down the concentration gradient.

Question 2

Is energy transferred during diffusion?

Answer 2

No as it is a passive process and happens because of the ordinary motion of the particles

Question 3

Diffusion continues until …

Answer 3

The concentration of the particles is the same everywhere. At this point the concentration gradient is 0

Question 4

What factors affect the rate of diffusion?

Answer 4

• the distance the particles need to move
• the concentration gradient
• the surface area

Question 5

How does distance affect the rate of diffusion

Answer 5

To increase the rate of diffusion you need to :

Decrease the DISTANCE that the particles need to move. This is because it takes less time to travel a shorter distance.

Question 6

How does the concentration gradient affect the rate of diffusion

Answer 6

To increase the rate of diffusion you need to:

• increase the concentration gradient. The steeper the concentration gradient the greater the net movement of particles.

Question 7

How does surface area affect the rate of diffusion

Answer 7

To increase the rate of diffusion you need to:

• increase the surface area. This allows more space for diffusion so more particles can move in a period of time.

Question 8

What is osmosis?

Answer 8

It is a type of diffusion

It is the movement of water molecules from a high water potential to a lower water potential (down a concentration gradient) across a selectively permeable membrane

Question 9

What is water potential?

Answer 9

It is the concentration of free water molecules

Question 10

What will happen to the number of feee water molecules if a solute dissolves in water

Answer 10

There will be fewer water molecules that are free to diffuse to other areas as the water molecules will cluster around the solute molecules.

Question 11

The more concentrated a solution becomes…

Answer 11

The lower the water potential

Question 12

What happens in a plant cell when the surroundings are less concentrated (have a higher water potential) than the cell contents ? ( if it is placed in a dilute solution)

Answer 12

If the cell is placed in a dilute solution it will take in water by osmosis .

The pressure in the cell increases. This pressure is caller turgor pressure

The cell becomes firm/ turgid.

Question 13

What happens if a plant cell is placed into a solution with the same concentration as its contents?

Answer 13

There is no net movement of water molecules. The cell stays the same

Question 14

What happens if a plant cell is placed in a more concentrated solution?

Answer 14

It looses water by osmosis.

The turgor pressure falls

The cell becomes flaccid (soft)

The cell contrasts collapse away from the cell

It becomes a plasmolysed cell

Question 15

What happens if an animal cell is placed into a solution that is more dilute than its contents?

Answer 15

It takes up water, swells and may burst. This is called Lysis

Question 16

What happens if an animal cell is placed into a solution with the same water potential as its cell contents?

Answer 16

There is no net movement of water. The cell stays the same

Question 17

What happens if an animal cell is placed into a more concentrated solution?

Answer 17

It loses water by osmosis.

The cent becomes crenated (crinkled)

Question 18

What is active transport

Answer 18

The transport of particles from an area of low concentration to an area of high concentration, against a concentration gradient using ATP (energy).

Question 19

What are three main things about active transport

Answer 19

• particles are transported/pumped against the concentration gradient
• ATP is required- this comes from respiration
• it makes use of carrier proteins in the cell membrane

Question 20

Why do cells that carry out active transport contain a lot of mitochondria

Answer 20

Because having lots of mitochondria means that cells can respite rapidly to produce large quantities of ATP

The rate of active transport depends on the rate of respiration to produce the requires ATP.

The greater the rate of respiration the greater the rate of active transport

Question 21

What are carrier proteins?

Answer 21

They are special proteins that span the width of the cell membrane .

Question 22

What do carrier proteins do?

Answer 22

• a particular molecule that the cell needs binds to a specific carrier protein.
• energy is transferred from an energy store to the protein to it can change shape or rotate.
• the carrier protein transports the molecule into the cell

Question 23

How do we use active transport during digestion?

Answer 23

In the small intestine carbohydrates are broken down into glucose.

The glucose is actively transported into the bloodstream through the villi.

The blood takes the glucose wherever it is needed in the body.

Question 24

How is active transport used in nerve cells?

Answer 24

A carrier protein actively pumps sodium ions out of the cell. At the same time potassium ions are pumped back in.

Question 25

How do plants use active transport?

Answer 25

To take minerals from the soil.

E.g Plants need nitrate ions to make proteins for growth. There is normally a lower concentration of nitrate ions in the soil surrounding the roots than in the plants.

The plant root hair cells use active transport to move the ions across the cell membrane and into the root cell