Exchange Of Materials

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 osmosis a type of?

Answer 2

Diffusion.

Question 3

Why does the concentration in the cells need to remain the same?

Answer 3

So that they can work properly.

Question 4

What is the concentration of tissue fluid used for?

Answer 4

It is usually different to the concentration inside a cell so water will move into or out of the cell.

Question 5

How does the cytoplasm regulate?

Answer 5

If it uses up water in chemical reactions the cytoplasm becomes more concentrated and water moves in by osmosis. On the other hand if the cytoplasm becomes too dilute, water leaves the cell by osmosis.

Question 6

What are the problems with osmosis?

Answer 6

If the solution outside the cell is more dilute than the cell contents, water will move into the cell by osmosis. The cell may swell and burst. If the concentration outside the cell is more concentrated the cell will shrivel up.

Question 7

Why do plants need osmosis?

Answer 7

They rely on it to support their stems and leaves.

Question 8

What happens when water moves into the cell of a plant?

Answer 8

The vacuole swells and presses the cytoplasm against the cell walls. he pressure builds up until no more water can enter. This makes the cell hard and rigid.

Question 9

What is active transport?

Answer 9

When substances are moved through a partially permeable membrane against the concentration gradient.

Question 10

What does active transport enable to happen?

Answer 10

Cells can absorb ions from very dilute substances. Substances such as sugars and ions can also be moved.

Question 11

Where does the energy for active transport come from?

Answer 11

Cellular respiration.

Question 12

How are root hair cells adapted for absorbing water and minerals?

Answer 12

They have a big surface area. They also have long hairs which stick out into the soil.

Question 13

How do root hair cells take in minerals?

Answer 13

Using active transport.

Question 14

When is active transport used in humans?

Answer 14

When taking glucose from the gut and from the kidney tubules.

Question 15

How can the effectiveness of exchanging materials be increased?

Answer 15

Having a large surface area, being thin to provide a short diffusion path, having an efficient blood supply, this moves the diffusing substances away and maintains the concentration gradient, being ventilated, to maintain the gaseous exchange and steep concentration gradient.

Question 16

How do stomata help with gas exchange?

Answer 16

They let carbon dioxide diffuse through, and let oxygen and water diffuse out of the stomata.

Question 17

How do the guard cells help with water loss?

Answer 17

Thy close the stomata if the plant is losing water faster than it is being replaced by the roots. Without them the plant will soon wilt.

Question 18

How does the flattened shape help the plant?

Answer 18

Increases the surface area.

Question 19

How do the air spaces help the plant?

Answer 19

Increases the amount of CO2 which can get into the cell.

Question 20

In the body where does gas exchange take place?

Answer 20

In the lungs there are millions of air sacs called alveoli.

Question 21

How are the alveoli adapted to maintain the concentration gradient.

Answer 21

They have an enormous surface area, a moist lining for dissolving gases, very thin walls, a good supply of blood.

Question 22

How is the thorax separated from the digestive organs?

Answer 22

The diaphragm.

Question 23

What is the diaphragm?

Answer 23

A strong sheet of muscle.

Question 24

How does air get into the blood?

Answer 24

The air which is breathed in goes through the trachea. This splits into two tubes called bronchi, one going to each lung. The bronchi split into progressively smaller tubes called bronchioles. The bronchioles then end up at the alveoli, where gas exchange takes place.

Question 25

What happens when you breathe in?

Answer 25

Intercostal muscles and diaphragm contract, thorax volume increases, this decreases the pressure drawing air in.

Question 26

What happens when you breathe out?

Answer 26

Intercostal muscles and diaphragm relax, thorax volume decreases, this increases the pressure, so air is forced out.

Question 27

Why may people need artificial ventilators?

Answer 27

The tubes leading to the lungs may be very narrow so less air gets through them. The structure of the alveoli can break down. Some people are paralysed in an accident or by disease so they can’t breathe.

Question 28

What two main ways to artificial breathing aids work?

Answer 28

Negative pressure and positive pressure.

Question 29

What kind of pressure is the iron lung?

Answer 29

Negative pressure.

Question 30

Why was the iron lung originally made?

Answer 30

Polio was a disease that left people unable to breathe.

Question 31

How do iron lungs work?

Answer 31

Patients lay in a metal chamber with their head sticking out.
Air was pumped out of the chamber, lowering the pressure and creating a vacuum.
As a result the chest wall of the patient moved up. This increased the volume and decreased the pressure inside the chest, so air was drawn out.
The vacuum was them switched off, so air returned to the cylinder increasing pressure.
The ribs moved down, lowering volume and increasing the pressure inside the thorax, forcing air out of the lungs.

Question 32

How do positive pressure ventilators work?

Answer 32

It can be given using a face mask or by a tube going into the trachea. Positive pressure bag ventilators are held and squeezed by doctor or nurses.

Question 33

What are the benefits of positive pressure ventilators?

Answer 33

The patient doesn’t have to be placed in the iron lung. Equipment can be used at home and the patient can be moved about. Patients can have control over the machine.

Question 34

How are the villi adapted?

Answer 34

They increase the surface area in a big way so that digested food us absorbed more quickly into the blood. They have a single layer of surface cells and a very good blood supply to assist quick absorption. Covered in microvilli.

Question 35

How is active transport used in the gut?

Answer 35

Glucose and other dissolved food molecules are then moved from the small intestine into the blood by active transport?

Question 36

Why is active transport important in the gut?

Answer 36

Makes sure that none of the digested food is wasted and lost in faeces.

Question 37

What do plant roots contain which helps them with active transport?

Answer 37

Mitochondria to supply the energy they need.

Question 38

How is transpiration caused?

Answer 38

The evaporation and diffusion of water from inside the leaves.

Question 39

What is transpiration?

Answer 39

The loss of water from the plant.

Question 40

What is the transpiration stream?

Answer 40

The constant movement of water molecules through the xylem from the roots to the leaves.

Question 41

Anything that increases the rate of photosynthesis will also increase the rate of what?

Answer 41

Transpiration, as the stomata are open to let more CO2 in, but this also lets water out.

Question 42

How do plants control water loss?

Answer 42

Most leaves have waxy, waterproof layers. Stomata are found on the underside of the leaf. Plant will wilt if too much water is being lost. Stomata will close.

Question 43

What do potometers measure?

Answer 43

The uptake of water not transpiration.