Transport

Question 1

Why can unicellular organisms rely on diffusion for the movement of their substances but multicellular organisms cannot?

Answer 1

They have a large surface area to volume ratio and they are relatively small, so diffusion can take place quickly. On the other hand, multicellular organisms have a small surface area to volume ratio and are large. This means that diffusion would be very slow and is why we have developed transport systems.

Question 2

What tubes in plants transport water and in what direction does the water go?

Answer 2

Xylem tubes transport water and they go from the roots up to the shoots.

Question 3

What tube in plants transport sucrose and amino acids and what direction does this go?

Answer 3

Phloem tubes transport sucrose and amino acids in all directions.

Question 4

Apart from the roots, how else do plants take in water?

Answer 4

The cells on plant roots grown into long hairs which stick out into the soil. Each branch of a root is also covered in millions of microscopic hairs, giving the plant a larger surface area to absorb water in my osmosis.

Question 5

What is transpiration?

Answer 5

The evaporation and diffusion of water from a plants surface (mainly from leaves).

Question 6

What stream do we say water is carried in?

Answer 6

The transpiration stream.

Question 7

How is the transpiration stream maintained? (Describe steps of transpiration)

Answer 7

1) water evaporates from the surface of a plant.
2) this evaporation creates a slight shortage in water. Due to the polarity of water molecules and its cohesion between the tubes, water is drawn up by xylem vessels to replace the water lost.
3) this in turn means that more water is needed to be drawn up from the roots, creating a constant transpiration stream of water through the plant.

Question 8

How does light intensity affect transpiration?

Answer 8

The more light there is, the greater the transpiration rate. if there is light, plants can carry out photosynthesis so the stomata open as guard cells are turgid. This means that the plant loses more water.

Question 9

How does temperature affect effect the rate of transpiration?

Answer 9

If there is more heat, water molecules have more kinetic energy to evaporate and diffuse. Therefore if the temperature is high, so is the transpiration rate.

Question 10

How does windspeed affect transpiration?

Answer 10

The higher the windspeed, the higher the transpiration rate. If windspeed is high, water vapour is constantly moved away so there is a concentration gradient.

Question 11

How does humidity affect transpiration rate?

Answer 11

If the air is humid, there are a lot of water molecules. This means that there is not a big concentration gradient and that transpiration doesn’t take place as much.

Question 12

What experiment can you carry out to see how the transpiration rate is affected?

Answer 12

1) At a slant, cut a plant root under water and assemble a photometer under water too.
2) remove the apparatus from the water, apart from the capillary tube, and make sure that the apparatus is air and water tight.
3) dry the leaves and leave for 10-15 minutes so that they can acclimatise.
4) remove the capillary tube from the water until an air bubble is formed and record its position.
5) start a stopwatch and record the distance moved.

Question 13

What do we assume the water loss in a photometer equals to?

Answer 13

Water loss= water loss from transpiration.

Question 14

What is the composition of blood?

Answer 14

Plasma
Platelets
Red blood cells
White blood cells

Question 15

What does blood carry?

Answer 15

Hormones
Digested food (glucose amino acids)
Waste substances (carbon dioxide and urea)
Heat energy

Question 16

What are the adaptations of the red blood cell?

Answer 16

Biconcave: this increases the surface area for oxygen to diffuse
Small size: allows them to fit through narrow capillaries
Haemoglobin: to absorb oxygen in the lungs and deliver it around the body.
No nucleus: frees up space for more haemoglobin to absorb oxygen.

Question 17

How do phagocytes work?

Answer 17

Phagocytes detect things that are foreign to the body, e.g. Pathogens. They have a grainy cytoplasm which contains sacks of enzymes so that they can engulf and digest pathogens.

Question 18

How do lymphocytes work?

Answer 18

They release antibodies that are specific to the antigens of the pathogen. They divide into two. One becomes a memory cell (so that you are not affected by the pathogen again) and the other half divide into 3 sets of antibodies.
One set attaches themselves to the pathogens so that they are marked out for destruction by the phagocytes.
Another set tries to disable the cell.
The other groups phagocytes together so that they can engulf and digest the pathogen.

Question 19

What happens in a vaccination?

Answer 19

Am inactive microbe is inserted into you to trigger your immune system. White blood cells work together and eventually destroy the pathogen and a memory cell is made so that you are never affected by the pathogen again.

Question 20

How does our blood clot?

Answer 20

When our blood vessels detect damage, a series of reactions take place to convert fibrinogen (a soluble fibre) into fibrin (insoluble). This acts as a plaster to prevent loads of blood loss and to stop pathogens from entering your body.

Question 21

What is the heart?

Answer 21

A muscular pump that delivers oxygen around the body. The left side is oxygenated and the right side is deoxygenated.

Question 22

What are the four heart chambers? And what do they do?

Answer 22

Left and right atrium and ventricle.
Atria- collect blood
Ventricle- pump blood around the body.

Question 23

What is the effect of exercise on our heart rate?

Answer 23

During exercise, our muscles need more energy for respiration and so we need more oxygen to be delivered to our cells and more car in dioxide taken away. In order to achieve this, adrenaline is released from our adrenal glands to increase the rate at which out heart works. This means that we breath more heavily, so we take in more oxygen.

Question 24

What is the role and structure of arteries?

Answer 24

Arteries take blood away from the heart at high pressure and speed. This means that the walls need to be strong, which is why they are thick and muscular and have narrow lumens. All arteries contain oxygenated blood (apart from the pulmonary artery) and move blood at very high pressure as oxygen is needed by important organs and tissues.

Question 25

What is the role and structure of veins?

Answer 25

Veins carry deoxygenated blood to the heart at low pressure and speed as it is returning from organs. They have relativ,eye thin walls, large lumens and smooth surfaces. All veins carry deoxygenated blood (apart from the pulmonary vein).

Question 26

What is the structure of a capillary?

Answer 26

Capillaries have very thin walls (1 cell thick) so that substances have a short distance for diffusion. They are where exchange takes place between blood and body cells.