B2.2 - Exchange & Transport

Question 1

Why is a large surface area to volume ration important in very small organisms(tapeworm)

Answer 1

Nutrients can diffuse directly into organism quickly enough to sustain life, as diffusion distances are small

Question 2

Why can’t most multicellular organisms used simple diffusion to survive?

Answer 2

Bigger organisms have lower surface area:volume ratios

Diffusion over the greater distance can’t occur fast enough to meet cells demands

Question 3

Exchange surface:

Answer 3

= an area where materials are interchanged

Question 4

How do lungs maximise the rate of diffusion of oxygen into bloodstream

Answer 4

= contain many alveoli which increase surface area of lungs, ensure efficient gas exchange

Question 5

How does the small intestine maximise the diffusion rate of digested food molecules into the blood

Answer 5

Walls of small intestine contain finger like villi, increase surface area of intestine wall
Microscopic microvilli on villi increase surface area further

Question 6

Circulatory system:

What is it made up of?

Answer 6

= Main transport system in animals

Made up of heart & blood vessels

Question 7

Why is the circulatory system a closed system?

Answer 7

As blood remains within these structures (heart & blood vessels)

Question 8

What does blood do in the circulatory system?

Answer 8

• transports substances around body to cells that need them (oxygen, glucose for respiration)
• carries away waste products (carbon dioxide)

Question 9

Why do we have a double circulatory system?

Answer 9

Blood flows through the heart twice during each circuit of the body

Question 10

Explain the process of the circulatory system:

Answer 10

• heart pumps blood to body organs & tissues
• oxygen & glucose diffuse out of blood into cells
• carbon dioxide diffuses out of cells into blood
• blood travels back to heart, pumps it to the lungs
• in lungs, carbon dioxide diffuses out of blood to be removed from body, oxygen diffuses in
• blood returns to heart & cycle repeats

Question 11

3 types of blood vessel

Answer 11

• arteries
• veins
• capillaries

Question 12

Blood vessel:

Answer 12

= tubelike structures that transport blood around body

Question 13

Lumen:

Answer 13

= hollow cavity in the centre of blood vessels

Question 14

Arteries function & structure

Answer 14

Carry blood away from heart under high pressure

• thick outer wall
• thick layer of muscle & elastic fibres
• small lumpen
• smooth lining

Question 15

Vein function & structure

Answer 15

Return blood to heart, have valves

• fairly thin outer wall
• thin layer of muscle & elastic fibres
• large lumen
• smooth lining

Question 16

Capillary function & structure:

Answer 16

Link arteries & veins in tissues & organs, form network so every cell is close to a capillary

• semipermeable wall, only 1 cell thick
• very small lumen

Question 17

Why do capillaries have semipermeable, one cell thick walls

Answer 17

So substances can easily move through them

Question 18

Why do arteries have thick & muscular walls?

Why do arteries have a thick layer of muscles & elastic fibres?

Answer 18

= To withstand the high pressures of blood caused by strong contractions of heart

= Wall expands with force of each contraction then snaps back(recoil) to push blood forward

Question 19

Why don’t veins need thick, muscular walls?

Answer 19

As blood pressure falls away from heart, pressure in veins is very low

Question 20

Why do veins contain valves?

Answer 20

Valves keep blood flowing in one direction, as the pressure is low in the veins, the valves are needed to make sure it flows back to the heart

Question 21

Why is the blood in a double circulatory system under higher pressure than a single one?

Answer 21

For each journey around the body, the blood is pumped twice

High pressure means materials transported quickly around body, essential for larger organisms

Question 22

What is a heart made of? Why is it different from other cells?

Answer 22

= cardiac muscle

Cardiac muscle cells contract without receiving a nerve impulse from your brain

Question 23

Four chambers of the heart:

Answer 23

• right atrium (top)
• left atrium (top)
• right ventricle (bottom)
• left ventricle (bottom)

(Opposite left & rights as on picture)

Question 24

What is blood made up of?

Answer 24

• red blood cells
• white blood cells
• plasma
• platelets

Question 25

Red blood cells

Answer 25

• small biconcave cells with no nucleus
• contain haemoglobin, carry oxygen
• fit though lumen of capillary 1 cell at a time

Question 26

White blood cells

Answer 26

• large cells, contain a nucleus

- fight disease by making antibodies/changing shape to engulf microorganisms

Question 27

Plasma

Answer 27

• liquid that blood cells float in
• 90% water, materials transported by dissolving in plasma
  (Amino acid, glucose, CO2, hormones, antibodies)

Question 28

Platelets

Answer 28

• tiny structures that help blood clot

Question 29

Factors affecting transpiration

Answer 29

• light intensity
• temperature
• air movement (wind)
• humidity