3. Movement into and out of cells

Question 1

Diffusion

Answer 1

The net movement of particles from a region of their higher concentration to a region of their lower concentration, down a concentration gradient, as a result of their random movement.

Substances move into and out of cells by diffusion thorugh the cell membrane.

Question 2

Factors affecting diffusion

Answer 2

• The temperature increases (due to an increase in kinetic energy)
• The distance decreases
• The surface area increases
• The concentration gradient increases.

Question 3

Passive process

Answer 3

Means no energy is needed. Particles will anturally move due to their own energy, organism doesn’t have to provide any energy.

Question 4

Factors affecting diffusion (temperature)

Answer 4

Increasing temperature = increasing diffusion rate

This is bc the particles have mroe energy and thus move more so they collide against each other more frequently + spread out faster.

Question 5

Factors affecting diffusion (Concentration gradient)

Answer 5

Higher difference in concentration = faster diffusion rates

If the concentrations on both sides are nearly equal the diffusion rate will be much slower.

Question 6

Factors affecting diffusion (Surface Area to Volume)

Answer 6

Larger surface area to volume = faster diffusion rates

This is because there is a larger area upon which the particles can move across (diffuse).

Question 7

Factors affecting diffusion (distance)

Answer 7

Smaller distances = faster diffusion

This is because the particles have to travel a shorter distance. Common sense lol.

Question 8

Water Potential

Answer 8

A measure of the tendency of water to move from one area to another due to osmosis.

Question 9

Osmosis

Answer 9

(A type of diffusion - with water instead)

Osmosis is the diffusion of water molecules across a partially permeable membrane, which allows only certain substances to pass through.

The net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution), through a partially permeable membrane.

Question 10

Turgid

Answer 10

Describes a plant cell in which the turgor pressure is sufficient to keep the cell stiff.

In osmosis a cell becomes turgid when it gains a large amount of water.

Question 11

Turgor pressure

Answer 11

The water pressure inside a plant cell that presses against the cell wall.

Question 12

Flaccid

Answer 12

Describes a plant cell in which the turgor pressure is insufficient due to loss of water by osmosis.

Question 13

Plasmolysis

Answer 13

A process that occurs when a plant cell is placed in a concentrated solution. In a plasmolysed cell, the cytoplasm shrinks so much that the cell membrane is pulled away from the cell wall.

All the water leaves the cell therefore it will most likely die.

Question 14

Crenated

Answer 14

When an animal cell loses most of its water due to osmosis. (deflates kind of)

Question 15

Spherical

Answer 15

When an animal cell becomes round due to having absorbed a lot of water due to osmosis. Will most likely burst.

Question 16

How does diffusion differ in different states of matter?

Answer 16

Solid - Does not happen

Liquid - Slow bc the particles have less energy to randomly spread

Gases - Much faster bc the particles have more energy to randomly spread.

Question 17

When do particles move across a membrane using diffusion?

Answer 17

When there is a permeable membrane. This means particles can move across it.

This can also happen with a semi permeable membrane but it will only let certain substances through.

Question 18

What are some examples of diffusion in organisms?

Answer 18

Movement of carbon dioxide and oxygen in leaves.

Movement of glucose and other food molecules into and out of the blood.

Movement of carbon dioxide and oxygen in in the alveoli of the lungs.

Movement of water, glucose, urea and ions in the glomerulus and nephron of the kidney.

Question 19

Where does the energy causing diffusion come from?

Answer 19

Molecules and ions (actually all particles but kognity does not say that - ask Miss Chip why) have their own store of kinetic energy. The state of matter depends on the amount of energy particles have Diffusion is a passive process - therefore the kinetic energy comes from the particles (no external energy)

Question 20

Solvent

Answer 20

Substance, usually a liquid, that can dissolve other substances to form solutions.

Question 21

What functions does water (as a solvent) perform in our body?

IMPORTANT + Check that it is in the summary sheet

Answer 21

In the alimentary canal, water allows for digestion of food molecules as both the enzymes and food molecules are dissolved in water, allowing them to interact and the molecules to break down.

In the kidneys, the toxic waste urea and excess ions are filtered from the blood and excreted dissolved in water. This is what forms urine.

Our blood is responsible for transporting a variety of substances around our body. Many of these are dissolved in the water that forms our blood plasma. Glucose, proteins and hormones are just some examples.

Question 22

Cell membranes relationship with osmosis.

Answer 22

The cell membrane controls what enters and leaves the cell. It lets smaller particles, such as water particles, enter the cell through osmosis. However, larger particles such as ions and starches are unable to enter the cell.

• Useful in plant cells - water in the vacuole of the plant cell exerts pressure on the cell wall keeping the plant stabilised and not wilted. (turgor pressure)

(relates to turgid, flaccid, plasmolyzed cells.)

Question 23

What happens when you place potatoes in different concentrated solutions?

Answer 23

Concentrated solution - lose mass bc there is more water inside the potato to begin with.

Water - Gain mass bc there is more water outside the potato to begin with.

Question 24

Active transport

Answer 24

The movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration, using energy from respiration.

Question 25

Active transport (further explained)

Answer 25

Cell membranes have carrier proteins in them connecting one side of the membrane to the other. Carrier proteins (or protein carriers) are able to pick up substances that the cell needs and move them from outside to inside the cell.

The proteins can change their shape for this to happen.

The carrier proteins need ATP (energy from respiration) to move proteins.

Question 26

Active transport in plants

Answer 26

Plants need minerals to survive. An example of this is nitrate ions. However, nitrate ions are in high concentration in the root hair cells of the plant. There is a lower concentration of nitrate ions in the soil.

Therefore nitrate ions would be moving from a lower concentration (soil) to a higher concentration (root hair cells).

This is why active transport is needed for this process.