B4 Transport

Question 1

Double Circulatory System

Answer 1

A double circulatory system is one where the blood passes through the heart twice to do one complete circuit of the body.

There are essentially two ‘loops’:

• the first transports blood to the lungs.
• the second transports blood around the tissues of the body.

Question 2

Red blood cells

Answer 2

Red blood cells pick up oxygen from the air in your lungs and carry it to the cells where it is needed. Red blood cells have adaptations that make them very efficient at their job:
• They are biconcave discs. Being concave on both sides, gives them an increased surface area to volume ratio for diffusion.
• They are packed with a red pigment called haemoglobin that binds to oxygen.
• They have no nucleus, making more space for haemoglobin.

Question 3

Platelets

Answer 3

Platelets are small fragments of cells. They have no nucleus. They are very important in helping the blood to clot at the site of a wound. Blood clotting is a series of enzyme-controlled reactions that result in converting fibrinogen into fibrin. This produces a network of protein fibres that capture lots of red blood cells and more platelets to form a jelly-like clot that stops you bleeding to death.

Question 4

White blood cells

Answer 4

White blood cells are much bigger than red blood cells and there are fewer of them. They have a nucleus and form part of the body’s defence system against harmful microorganisms. Some white blood cells (lymphocytes) form antibodies against microorganisms. Some form antitoxins against poisons made by microorganisms. Yet others (phagocytes) engulf and digest invading bacteria and viruses.

Question 5

Blood plasma

Answer 5

Your blood plasma is a yellow liquid. The plasma transports all of your blood cells and some other substances around your 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 your blood to form urine.
• The small, soluble products of digestion pass into the plasma from your small intestine and are transported to the individual cells.

Question 6

Arteries

Answer 6

Your arteries carry blood away from your heart to the organs of your body. This blood is usually bright-red oxygenated blood. The arteries stretch as the blood is forced through them and go back into shape afterwards. You can feel this as a pulse where the arteries run close to the skin’s surface (e.g., at your wrist). Arteries have thick walls containing muscle and elastic fibres. As the blood in the arteries is under pressure, it is very dangerous if an artery is cut, because the blood will spurt out rapidly every time the heart beats.

Question 7

Veins

Answer 7

The veins 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. They have much thinner walls than arteries and often have valves to prevent the backflow of blood. The 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. The blood is squeezed back towards the heart by the action of the skeletal muscles.

Question 8

Capilleries

Answer 8

Throughout the body, capillaries form a huge network of tiny vessels linking the arteries and the veins. Capillaries are narrow with very thin walls. This enables substances, such as oxygen and glucose, to diffuse easily out of your blood and into your cells. The substances produced by your cells, such as carbon dioxide, pass easily into the blood through the walls of the capillaries.

Question 9

aorta

Answer 9

the artery that leaves the heart from the left ventricle and carries oxygenated blood to the body

Question 10

atria

Answer 10

the upper chambers of the heart

Question 11

coronary arteries

Answer 11

the blood vessels that supply oxygenated blood to the heart muscle

Question 12

haemoglobin

Answer 12

the red pigment that carries oxygen around the body in the red blood cells

Question 13

plasma

Answer 13

the clear yellow-liquid part of the blood that carries dissolved substances and blood cells around the body

Question 14

pulmonary artery

Answer 14

the large blood vessel that takes deoxygenated blood from the right ventricle of the heart to the lungs

Question 15

pulmonary vein

Answer 15

the large blood vessel that carries oxygenated blood from the lungs back to the left atrium of the heart

Question 16

statins

Answer 16

drugs used to lower blood cholesterol levels and improve the balance of high- to low-density lipoproteins in the
blood

Question 17

stent

Answer 17

a metal mesh placed in a blocked or partially blocked artery. They are used to open up the blood vessel by the
inflation of a tiny balloon

Question 18

vena cava

Answer 18

the large vein that brings deoxygenated blood from the body into the heart

Question 19

ventricles

Answer 19

chambers of the heart that contract to force blood out of the heart

Question 20

aphids

Answer 20

insects that penetrate the plant phloem and feed on dissolved food. They acts as vectors that carry pathogenic
viruses, bacteria and fungi into healthy plant tissue

Question 21

epidermal

Answer 21

the name given to cells that make up the epidermis or outer layer of an organism

Question 22

guard cells

Answer 22

surround the stomata in the leaves of plants and control their opening and closing

Question 23

palisade mesophyll

Answer 23

the upper layer of the mesophyll tissue in plant leaves made up of closely packed cells that contain many
chloroplasts for photosynthesis

Question 24

phloem

Answer 24

the living transport tissue in plants that carries dissolved food (sugars) around the plant

Question 25

spongy mesophyll

Answer 25

the lower layer of mesophyll tissue in plant leaves that contains some chloroplasts and many large air spaces to
give a big surface area for the exchange of gases

Question 26

translocation

Answer 26

the movement of sugars from the leaves to the rest of the plant through the phloem

Question 27

transpiration

Answer 27

the loss of water vapour from the leaves of plants through the stomata when they are opened to allow gas
exchange for photosynthesis. It involves evaporation from the surface of the cells and diffusion through the
stomata

Question 28

xylem

Answer 28

the non-living transport tissue in plants that transports water from the roots to the leaves and shoots

Question 29

Factors Affecting Rates of Transpiration (wind)

Answer 29

Windier conditions increase transpiration because the leaf’s boundary layer is smaller.

Question 30

Factors Affecting Rates of Transpiration (light)

Answer 30

Light levels as low as one thousandth of the sun can cause stomata to open.

Question 31

Factors Affecting Rates of Transpiration (temperature)

Answer 31

Warmer air holds more water, creating a larger driving force for water movement out of the plant, increasing rates of transpiration.

Question 32

Factors Affecting Rates of Transpiration (humidity)

Answer 32

The drier the atmosphere, the larger the driving force for water movement out of the plant, increasing rates of transpiration.