B3 - Diffusion & Active Transport

Question 1

What is osmosis?

Answer 1

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

Question 2

What is a partially permeable membrane?

Answer 2

A membrane with very small holes in it so that only small molecules like water can pass through

Question 3

Why do some of the water molecules involved in osmosis go towards the high concentration region?

Answer 3

The water molecules move about randomly and sometimes deflect off another water molecules at the right angle so that it passes into the high concentration region
However, the net movement of the water molecules is towards the low concentration region

Question 4

How is osmosis used in the human body?

Answer 4

So that water or solutions can travel into and out of cells

Question 5

What decides if osmosis causes the water to go into or out of the cell?

Answer 5

If the cell is short of water, the concentration of water outside the cell will be higher so osmosis will bring water into the cell
If the cell has too much water, the opposite will occur

Question 6

What are the 3 ways in which substances move around living organisms?

Answer 6

Osmosis
Diffusion
Active transport

Question 7

What is diffusion?

Answer 7

Where substances move from an area of high concentration to an area of low concentration without the input of energy

Question 8

What is active transport?

Answer 8

Where substances move from an area of low concentration to an area of high concentration because another substance is carrying it
Active transport requires energy

Question 9

What is an exchange surface?

Answer 9

What the substances need to pass through

Question 10

What are the 2 ways that diffusion is used in plants?

Answer 10

Carbon dioxide diffuses through the stomata into the plant

Oxygen diffuses out of the plant through the stomata

Question 11

What are guard cells?

Answer 11

Cells that control the size of the stomata

They control the amount of water lost and make it equal to the amount of water coming into the plant through the roots

Question 12

In terms of diffusion, why are leaves flat?

Answer 12

To increase the area of the exchange surface making diffusion more effective

Question 13

Describe the process of gas exchange

Answer 13

Oxygen in the alveoli diffuses into the capillary network to get into the bloodstream
Carbon dioxide in the blood passes the alveoli and diffuses into them so that it can escape

Question 14

What are villi and how do they work?

Answer 14

Tiny hair-like projections on the inside of the small intestine that increase the surface area of the small intestine massively
The digested food is absorbed by the villi and it passes into the capillary network inside the villi

Question 15

What do alveoli and villi have in common?

Answer 15

They are both exchange surfaces

Question 16

What are root hairs?

Answer 16

Tiny hairs that stick out of the sides of the roots of s plant so that the roots have a larger surface area so that they absorb more mineral ions and water

Question 17

Describe how the minerals and water get from the soil into the root hairs

Answer 17

The concentration is higher inside the plant so active transport has to be used to get the minerals and water into the root hairs
Active transport requires energy from respiration to work though

Question 18

Describe how the digested food travels from the small intestine to the capillary network

Answer 18

There is a higher concentration of nutrients in the blood than in the small intestine meaning the nutrients are actively transported from the surface of the villi to the capillary network inside