Surface Area to Volume Ratio and Gas Exchange flashcards

Question 1

How does an organism’s size relate to their surface area to volume ratio?

Answer 1

The larger the organism, the lower the surface area to volume ratio.

Question 2

How does an organism’s surface area to volume ratio relate to their metabolic rate?

Answer 2

The smaller the surface area to volume ratio, the higher the metabolic rate.

Question 3

How might a large organism adapt to compensate for its small surface area to volume ratio?

Answer 3

• Changes that increase surface area
• body parts become larger
• elongating shape

Question 4

Why do multicellular organisms require specialised gas exchange surfaces?

Answer 4

• Their smaller SA: Volume ratio means the distance that needs to be crossed is larger
• Substances cannot easily enter the cells unlike single-celled organism.

Question 5

Name three features of an efficient gas exchange surface

Answer 5

1. Large surface area, e.g. folded membranes in mitochondria.
2. Thin/short distance, e.g. the wall of capillaries.
3. Steep concentration gradient, maintained by blood supply or ventilation, e.g. alveoli.

Question 6

Why can’t insects use their bodies as an exchange surface?

Answer 6

• They have a waterproof chitin exoskeleton

- a small SA:Volume ratio in order to conserve water.

Question 7

Name the three main features of an insect’s gas transport system.

Answer 7

● Spiracles

● Tracheae

● Tracheoles

Question 8

Explain the process of gas exchange in

insects.

Answer 8

• Gases move in and out of the tracheae through
  the spiracles.
• A diffusion gradient allows oxygen to diffuse into
  the body tissue while waste CO2 diffuses out
• Contraction of muscles in the tracheae allows
  mass movement of air in and out.

Question 9

Why can’t fish use their bodies as an exchange surface?

Answer 9

• They have a waterproof, impermeable outer membrane

- a small SA: volume ratio.

Question 10

Name the two main features of a fish’s gas transport system.

Answer 10

• Gills

- Lamella

Question 11

Explain the process of gas exchange in

fish.

Answer 11

1. The fish opens its mouth to enable water to flow in, then closes its mouth to increase pressure.
2. The water passes over the lamellae, and the oxygen diffuses into the bloodstream.
3. Waste carbon dioxide diffuses into the water
   and flows back out of the gills.

Question 12

How does the countercurrent exchange system maximise oxygen absorbed by the fish?

Answer 12

• Maintains a steep concentration gradient, as water is always next to the blood of a lower oxygen concentration.
• Keeps rate of diffusion constant.
• enables 80% of available oxygen to be absorbed.

Question 13

Name and describe three adaptations of

a leaf that allow efficient gas exchange.

Answer 13

1. Thin and flat
2. Many minute pores in the underside of the leaf (stomata).
3. Air spaces in the mesophyll allow gases to move around the leaf, facilitating photosynthesis.

Question 14

How do plants limit their water loss while

still allowing gases to be exchanged?

Answer 14

Stomata regulated by guard cells which allows them to open and close as needed. Most stay closed to prevent water loss while some open to let oxygen in.

Question 15

Describe the pathway taken by air as it
enters the mammalian gaseous
exchange system.

Answer 15

Nasal cavity → trachea → bronchi →

bronchioles → alveoli

Question 16

Describe the function of the nasal cavity
in the mammalian gaseous exchange
system.

Answer 16

• A good blood supply warms and moistens
  the air entering the lungs.
• Goblet cells in the membrane secrete mucus which traps dust and bacteria.

Question 17

Describe the trachea and its function in
the mammalian gaseous exchange
system.

Answer 17

● Wide tube supported by C-shaped cartilage to keep
the air passage open during pressure changes.

● Lined by ciliated epithelium cells which move
mucus towards the throat to be swallowed.

● Carries air to the bronchi.

Question 18

Describe the bronchi and their function in
the mammalian gaseous exchange
system.

Answer 18

● Like the trachea, they are supported by rings of
cartilage and are lined by ciliated epithelium cells.

● They are narrower and one for each lung.

● Allow passage of air into the bronchioles.

Question 19

Describe the bronchioles and their function in the mammalian gaseous exchange system.

Answer 19

• Narrower than the bronchi.
• Don’t need to be kept open by cartilage
• Mostly only muscle and elastic fibres so that
  they can contract and relax easily during ventilation.
• Allow passage of air into the alveoli.

Question 20

Describe the alveoli and their function in
the mammalian gaseous exchange
system.

Answer 20

• Mini air sacs, lined with epithelium cells, site of
  gas exchange.
• Walls only one cell thick, covered with a
  a network of capillaries.
• 300 million in each lung, all of which facilitates gas diffusion.

Question 21

Explain the process of inspiration and
the changes that occur throughout the
thorax.

Answer 21

● External intercostal muscles contract (while internal
relax), pulling the ribs up and out.

● Diaphragm contracts and flattens.

● The volume of the thorax increases.

● Air pressure outside the lungs is, therefore, higher than the inside, so air moves in to rebalance.

Question 22

Explain the process of expiration and the
changes that occur throughout the
thorax.

Answer 22

● External intercostal muscles relax (while internal
contract), bringing the ribs down and in.

● Diaphragm relaxes and domes upwards.

● Volume of the thorax decreases.

● Air pressure inside the lungs is higher than the air pressure outside, so air moves out to rebalance.

Question 23

What is tidal volume?

Answer 23

The volume of air we breathe in and out during each breath at rest.

Question 24

What is breathing rate?

Answer 24

The number of breaths we take per minute.

Question 25

How do you calculate pulmonary ventilation rate?

Answer 25

Tidal volume x breathing rate.

- can be measured using a spirometer

Question 26

What are Gills?

Answer 26

A respiratory organ supported by arches along which are multiple projections of gill filaments.

Question 27

What are Lamellae?

Answer 27

Lamellae = at right angles to the gill filaments, give an increased surface area. Blood and water flow across them in opposite directions (countercurrent exchange system).

Question 28

What are the benefits of leaves being thin and flat?

Answer 28

It provides a short diffusion pathway and a large SA: Volume ratio.

Question 29

What are the benefits of leaves having many minute pores?

Answer 29

It allows gases to easily pass through the stomata.

Question 30

What are the benefits of air spaces in the mesophyll?

Answer 30

It allows gases to move around the leaf, facilitating photosynthesis.

Question 31

What is a spirometer

Answer 31

A device that records volume changes onto a graph as a person breathes.

Question 32

What name is given to the term that describes the maximum volume of air that an individual can expire in one second?

Answer 32

Forced expiratory volume

Question 33

What is bronchitis?

Answer 33

Partial blocking of the airways with mucus