Exchange surfaces

Question 1

examples of diffusion in the body

Answer 1

oxygen and carbon dioxide in gas exchange, urea

Question 2

why do single celled organisms have large surface to volume ratios

Answer 2

so enough substances can be exchanged across the membrane

Question 3

how are exchange surfaces adapted

Answer 3

• they have a thin membrane, so substances only have a short distance to diffuse
• large surface area so a lot of a substance can diffuse at once
• lots of blood vessels , to get things in and out of the blood quickly
• well ventilated

Question 4

how are the lungs adapted to exchange substances

Answer 4

• job is to transfer oxygen to the blood and to remove waste carbon dioxide from it
• lungs contain alveoli where gas exchange takes place
• alveoli have large surface area
• alveoli have a moist lining for dissolving gases
• alveoli have thin walls
• alveoli have a good blood supply

Question 5

how are villi adapted to exchange substances

Answer 5

• they increase surface area in a big way so that digested food is absorbed more quickly into the blood
• they have a single layer of surface cells
• good blood supply to assist quick absorption
• short diffusion paths

Question 6

how are structures in plants adapted to exchange substances

Answer 6

• underneath the leaf covered in holes called stomata where co2 diffuses in
• oxygen and water vapour diffuse out of the stomata
• guard cells open and close the stomata depending on how much water the plant is losing
• flattened shape of leaf increases surface area so it’s more effective
• air spaces inside the walls of the leaf increase surface area so theres a higher chance of co2 getting inside cells

Question 7

how does ventilation and good blood supply help with exchange surfaces

Answer 7

The moving blood and ventilated surfaces mean that a steep concentration gradient can be maintained. This increases effective exchange

Question 8

what is a concentration gradient

Answer 8

the difference in the concentration of a chemical across a membrane

Question 9

emphysema is a disease which weakens and breaks down walls of the alveoli
- a person with this may suffer with low energy levels during physical excercise. why?

Answer 9

• as the walls of the alveoli break down, the surface area in the lungs is reduced
• meaning the amount of oxygen that can diffuse into the blood at one time is reduced
• this means that body cells wont get enough oxygen for respiration during exercise, resulting in lower energy levels

Question 10

how does the structure of the small intestine adapted to absorb the products of digestion

Answer 10

• covered in villi, which increases the surface area for absorption
• theres a good blood supply, which maintains a concentration gradient so absorption can happen quickly
• the villi have a single layer of cells which give them a short diffusion pathway

Question 11

how are gills adapted for efficient substance exchange

Answer 11

-gills are covered in filaments
- filaments give gills a large surface area
- filaments have a thin membrane to provide a short diffusion path
- filaments have an efficient blood supply to take the oxygenated blood away and this ensures that the concentration gradient is always high

Question 12

what gases enter and leave a plant

Answer 12

• co2 goes into the plant
• water vapour goes out
• oxygen diffuses out

Question 13

what is the purpose of air spaces in a leaf

Answer 13

they increase the surface area for carbon dioxide to diffuse into the cells

Question 14

where is the meristem found

Answer 14

growing tips of shoots
growing tips of roots