B4 Organizing animals and plants

Question 1

what are the adaptations of red blood cells?

Answer 1

• Biconcave discs, increased surface area to volume ratio for diffusion
• Packed with haemoglobin that binds to oxygen
• No nucleus, more space for haemoglobin which carries oxygen

Question 2

describe the function and structure of arteries

Answer 2

• Carry blood away from your heart to the organs of your body
• This blood is usually bright-red oxygenated blood
• Thick layer of muscle and elastic fibres
• Small lumen

Question 3

Why is it very dangerous if an artery is cut?

Answer 3

The blood in the arteries is under pressure, so blood will spurt out rapidly every time the heart beats if an artery is cut

Question 4

describe the function and structure of veins

Answer 4

• Carry blood away from the organs towards your heart
• This blood is usually low in oxygen and therefore a deep purple-red colour
• Veins do not have a pulse.
• Thinner walls than arteries and often have valves to prevent the backflow of blood
• Valves open as the blood flows through them towards the heart, but if the blood starts to flow backwards the valves close and prevent a backflow of blood
• Large lumen

Question 5

describe the function and structure of capillaries

Answer 5

• Form a huge network of tiny vessels linking the arteries and the veins
• Narrow with very thin walls (walls a single cell thick), enables substances (such as glucose and oxygen) to diffuse easily out of your blood and into your cells
• Tiny vessel with narrow lumen

Question 6

The blood plasma as a transport medium

Answer 6

The plasma transports all of the blood cells and some other substances around the body:
- waste carbon dioxide produced by the cells is carried to the lungs
- urea formed in your liver from the breakdown of excess proteins is carried to your kidneys where it is removed from the blood to form urine
- the small, soluble products of digestion pass into the plasma from the small intestine and are transported to the individual cells

Question 7

What is the function of heart valves?

Answer 7

Prevent back flow of blood

Question 8

What is the double circulatory system?

Answer 8

One part carries blood between heart and lungs; the other carries blood between heart and other organs

Question 9

what is the function of the vena cava?

Answer 9

Brings deoxygenated blood into the heart through the right atrium

Question 10

what is the function of the pulmonary vein?

Answer 10

Brings oxygenated blood from the lungs into the left atrium

Question 11

what is the function of the atria?

Answer 11

Top chambers of the heart where the blood enters; contract together to force blood down into the ventricles

Question 12

what’s the function of ventricles?

Answer 12

Contract and force blood out of the heart

Question 13

what is the function of the right ventricle?

Answer 13

Forces deoxygenated blood to the lungs in the pulmonary artery

Question 14

what is the function of the left ventricle?

Answer 14

Pumps oxygenated blood around the body in the aorta

Question 15

what is the function of the pulmonary artery?

Answer 15

Takes deoxygenated blood to the lungs

Question 16

what is the function of the aorta?

Answer 16

Carries oxygenated blood around the body

Question 17

Why is the muscle wall of the left ventricle thicker than the right ventricle?

Answer 17

To generate more pressure to force blood all over the body

Question 18

How do stents work?

Answer 18

• Used to keep narrow or blocked arteries open
• A stent is a metal mesh that is placed in the artery, a tiny balloon is inflated to to open up the blood vessel and the stent at the same time
• The balloon is deflated and removed but the stent remains in place, holding the blood vessel open
• The blood in the coronary artery flows freely
• Many stents also release drugs to prevent the blood clotting

Question 19

How do statins work?

Answer 19

• Reduce cholesterol levels in the blood, this slows down the rate at which fatty material is deposited in the coronary arteries
• Reducing the risk of coronary heart disease

Question 20

What are platelets?

Answer 20

Small fragments of cells that start the clotting process at wound sites

Question 21

State differences in the blood flowing in arteries and veins

Answer 21

Arteries:
- oxygenated blood
- contains more nutrients
- contains less waste

Veins:
- deoxygenated blood
- contains less nutrients
- contains more waste

Question 22

Why can substances diffuse easily between capillaries and the cells?

Answer 22

Capillary walls are very thin, only one cell thick, which provides short diffusion distances

Question 23

What is the function of xylem?

Answer 23

Transports water and mineral ions from roots to other parts of the plants

Question 24

What is the function of phloem?

Answer 24

Transports dissolved sugars from leaves to the rest of the plant

Question 25

What is transpiration?

Answer 25

Loss of water vapour by evaporation from the leaf surface through the stomata

Question 26

Describe the transpiration stream

Answer 26

Constant movement of water through xylem from roots to leaves

Question 27

Factors affecting rate of transpiration

Answer 27

• Temperature
• Humidity
• Air flow
• Light intensity

Question 28

How does temperature affect the rate of transpiration?

Answer 28

• Higher temperature increases the rate of transpiration, because the molecules move faster as the temperature increases, so diffusion occurs more rapidly
• The rate of photosynthesis also increases as the temperature increases, so more stomata will be open for gas exchange to take place

Question 29

How does humidity affect the rate of transpiration?

Answer 29

• Higher humidity decreases the rate of transpiration
• Humidity is a measure of moisture (water vapour) in the air; when the air is saturated with water vapour the concentration gradient is weaker so less water is lost

Question 30

How does wind or air flow affect the rate of transpiration?

Answer 30

More wind increases the rate of transpiration because it maintains a steep concentration gradient, so diffusion occurs rapidly

Question 31

How does light intensity affect the rate of transpiration?

Answer 31

• Greater light intensity increases the rate of transpiration
• Increased light intensity increases the rate of photosynthesis, so more stomata open up to let in carbon dioxide, the rate at which water is lost by evaporation and diffusion increases, therefore rate of transpiration increases

Question 32

Name the equipment used to estimate transpiration rate

Answer 32

Potometer

Question 33

What is the difference between translocation and transpiration?

Answer 33

Transpiration is the loss of water vapour by evaporation from the leaf surface through the stomata. Translocation is the movement of sugars from the leaves to the rest of the plant through the phloem.

Question 34

define the term double circulatory system

Answer 34

• blood is pumped to the lungs by the right side of the heart
• blood is pumped to the body by the left side of the heart

Question 35

explain how having only one ventricle makes the circulatory system less efficient than having two ventricles

Answer 35

• oxygenated and deoxygenated blood mixes
• so less oxygen reaches the body’s cells

Question 36

how does an artificial pacemaker work?

Answer 36

placed on the right atrium, sends strong, regular, electrical signals to the heart to stimulate it to beat properly

Question 37

describe how the structure of an artery is different from the structure of a vein

Answer 37

arteries have thick walls contain muscle and elastic fibres, veins have thin walls
arteries have a small lumen, veins have a large lumen