B3.1 Exchange of Materials

Question 1

Dissolved Substances move by which two processes? (2)

Answer 1

Diffusion and Active Transport

Question 2

Water often moves across boundaries by which process?

Answer 2

Osmosis

Question 3

Define Osmosis

Answer 3

Osmosis is the diffusion of water from a low concentration to a high concentration through a partially permeable membrane.

Question 4

Define Active transport

Answer 4

Active transport is the process by which dissolved molecules move across a cell membrane from a low concentration to a high concentration, against the concentration gradient. This requires the use of energy provided from respiration.

Question 5

The effectiveness of an exchange surface is increased by what 4 factors?

Answer 5

• Having a large surface area
• Being thin, to provide a short diffusion path.
• (in animals) having an efficient blood supply.
• (in animals, for gaseous exchange) being ventilated.

Question 6

In humans the surface area of the lungs is increased by which structure in the lungs?

Answer 6

The alveoli

Question 7

In humans the surface area of the small intestine is increased by which structure?

Answer 7

Villi

Question 8

How does the villi provided a larger surface area?

Answer 8

By having an extensive network of capillaries to absorb the products of digestion by diffusion and active transport.

Question 9

Where are the lungs located in the body, and are protected by what?

Answer 9

• Upper part of the body (thorax)

- Protected by the ribcage and separated from the lower part of the body (abdomen) by the diaphragm.

Question 10

When we breathe, which gas diffuses in, and which gas diffuses out?

Answer 10

• Oxygen diffuses into the bloodstream

- Carbon Dioxide diffuses out of the bloodstream into the air.

Question 11

What happens when we breathe in? (4)

Answer 11

• Intercostal muscles between the ribs and the diaphragm contract.
• Ribcage moves out and up, and diaphragm becomes flatter.
• Volume of the thorax increases.
• Pressure of the thorax decreases as air is drawn in.

Question 12

What happens when we breathe out? (4)

Answer 12

• The intercostal muscles of the ribcage and diaphragm relax.
• The ribcage moves down and in and the diaphragm becomes domed.
• The volume of the thorax decreases.
• The pressure increases and air is forced out.

Question 13

The movement of air into and out of the lungs is know as what process?

Answer 13

Ventilation

Question 14

Give three reasons why a person may not be able to get enough oxygen into their bloodstream? (3)

Answer 14

• If the alveoli are damaged, the surface area for gas exchange is reduced.
• If the tubes leading to the lungs are narrowed, less air can be moved through them.
• If the person is paralysed, their muscles will not work to pull the ribcage up and out.

Question 15

Describe the process of how an ‘iron lung’ works. (4)

Answer 15

• Used for people with polio who are paralysed.
• Covers the whole body of the patient apart from the head.
• The pressure in the capsule (iron lung) is mechanically lowered to allow the lungs to expand and take in air and then raised to make the lungs contract and expel air.
• However the blood flow in the lower part of the body can be poor and cause an increase in circulation side effects.

Question 16

How are modern ventilators better than the iron lung? (4)

Answer 16

• Modern ventilators work by pumping air in a go/stop cycle, using a mouth piece connection, directly into the lungs to expand them and push out the ribcage.
• When the pump temporarily stops, the ribcage relaxes, allowing the lungs to contract and get rid of the air.
• This is a much more convenient method, and it doesn’t interfere with the body’s blood supply.
• However there can be problems if the alveoli bursts, then the body can’t cope with the artificially increased air supply.

Question 17

What do most sport drinks contain, which is vital during exercise or other physical activities? (3)

Answer 17

• Water to replace water lost when sweating.
• Glucose (sugar) to replace the sugar used for energy released in exercise.
• Mineral ions to replace those lost in sweating.

Question 18

What does the term “isotonic” mean, with regards to sport drinks?

Answer 18

If the drink concentration matches the body fluids the solution is called isotonic.

Question 19

Define transpiration?

Answer 19

The loss of water vapour from the leaves of plants through the stomata when they are opened to allow gas exchange for photosynthesis.

Question 20

In plants Carbon dioxide enters the leaves by which process?

Answer 20

Diffusion

Question 21

In plants most of the water and mineral ions are absorbed by which plant organ?

Answer 21

Roots.

Question 22

What increases the surface area of the roots?

Answer 22

Root Hairs

Question 23

What increases the surface area of leaves?

Answer 23

Increased by flattened shape and internal air spaces.

Question 24

What is the role of the stomata?

Answer 24

Stomata open and close, allowing CO2 in, and O2 out during the process of photosynthesis.

Question 25

Plants mainly lose water vapour from which side of the stomata.

Answer 25

Plants lose most of their water from the underside of their stomata.

Question 26

Evaporation is more rapid in what sort of conditions? (3)

Answer 26

Hot, dry, and windy conditions.

Question 27

The opening and closing of the stomata is controlled by which group of cells?

Answer 27

Guard Cells.