B2.1

Question 1

Define diffusion

Answer 1

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

Question 1

How does temperature affect diffusion?

Answer 1

As the temperture increases, the rate of diffusion increases as the particles have more kinetic energy to move faster

Question 2

How does the concentration gradient affect diffusion?

Answer 2

The greater the concentration gradient, the higher the rate of diffusion because if there is a higher ratio of particles on one end of the gradient, then this will allow more particles to diffuse at once

Question 3

How does the surface area of the membrane affect diffusion?

Answer 3

The larger the surface area of the membrane, the higher the rate of diffusion because this provides more space for the particles to move through

Question 4

How does diffusion distance of the membrane affect the rate of diffusion?

Answer 4

The shorter the diffusion distance, the higher the rate of diffusion because it will take less time for the particles to move through the membrane.

Question 5

Define osmosis

Answer 5

The net movement of water molecules from a region of high water potential to a region of low water potential across a partially permeable membrane.

Question 6

Which process transfers water from the soil to the roots?

Answer 6

Osmosis

Question 7

Which process transfers mineral ions from the soil to the roots

Answer 7

Active transport

Question 8

If blood is mixed in a solution with more solute concentration than inside the blood, what will happen to the cell?

Answer 8

The cell will turn crenated because the solution is hypotonic and a higher solute concentration means a lower water concentration. So, the red blood cells will lose water by osmosis since there is an higher water concentration in the cell than outside of the cell until it becomes crenated (crinkled).

Question 9

If blood is mixed with a dilute solution, what will happen to the cell?

Answer 9

The cell will burst because the solution is hypertonic so there is a higher concentration of water outside of the cell than inside. The cell will gain so much water by osmosis that it will swell and eventually burst.

Question 10

Define active transport

Answer 10

The movement of particles from a region of low concentration to a region of high concentration against the concentration gradient using ATP (energy).

Question 11

During which phase of the cell cycle does mitosis happen?

Answer 11

Cell division

Question 12

What is the surface area to volume ratio of a cube of 3x3x3 cm?

Answer 12

2:1

Question 13

Describe how lungs are adapted to increase rate of gas exchange

Answer 13

They have alveoli which:
- have a high sa:vol ratio
- Capillary network
- shorter diffusion distance

Question 14

What is cell differentiation?

Answer 14

When cells become specialised to perform a particular function

Question 15

How are sperm cells specialised to their function?

Answer 15

They have:
- flagellum - helps them move through liquids and into the ovum (egg)
- lots of mitochondria - for maximum respiration which provides lots of energy for the flagellum to move
- enzyme acrosome —> stores digestive enzymes which break down the outer layers of the ovum to allow the sperm to transfer genetic material to the ovum

Question 16

How are nerve cells adapted to carry impulses?

Answer 16

• they have a long axon to transport the impulse at long distances
• they have extensions to connect to other nerve cells and contain neurotransmitters to transmit the impulse

Question 17

How are root hair cells specialised to take up water and minerals

Answer 17

• large sa:volume ratio for shorter diffusion distance
• lots of mitochondria to generate energy for active transport of mineral ions

Question 18

What are stem cells?

Answer 18

undifferentiated cells that can develop into a different types of cells to perform a certain action for the body

Question 19

Where are adult stem cells found?

Answer 19

In the bone marrow

Question 20

Where are embryonic stem cells found?

Answer 20

In the embryo

Question 21

How is an embryonic stem cell formed?

Answer 21

When a sperm fertilises an egg, a zygote is created. Then it undergoes mitosis to form a small group of cells called the embryo. Each cell in the embryo (embryonic stem cell) differentiate into all types of cells.

Question 22

Where are plant stem cells found?

Answer 22

In the meristems of the plant (roots and shoots)

Question 23

What are stem cells used for?

Answer 23

Growth and repair

Question 24

How are red blood cells specialised to carry oxygen?

Answer 24

• biconcave structure —> increases sa:volume ratio to allow more gas exchange
• no nucleus —> creates more space for more oxygen to be transported around the body
• lots of haemoglobin —> red hormone that helps the cell to bind to oxygen easily

Question 25

How are cilliated cells adapted to sweep away dust, bacteria, mucus and hair?

Answer 25

They have hair like structures called cillia which sweep the dust, bacteria, mucus and hair from the airways to the back of the throat which is then swallowed to prevent it clogging up in the airways and then the lungs.