Specialised Exchange Surfaces & Gaseous Exchange Systems In Mammals

Question 1

Give examples of materials that need to be exchanged across a surface

Answer 1

• oxygen & glucose for metabolic reactions
• carbon dioxide & urea need to be excreted
• water
• fats
• minerals

-amino acids

Question 2

What are the two ways in which substances can move across an exchange surface?

Answer 2

• passively= no energy required e.g diffusion

- actively= energy required e.g active transport

Question 3

How do you calculate surface area to volume ratio?

Answer 3

-surface area: 2 (length x height)
2 (length x width)
2 (height x width) : total cm squared

-volume: length x width x height cm cubed

Divide SA by volume = sa:v

Question 4

Explain why multicellular organisms need exchange surfaces but single-celled organisms don’t.

Answer 4

-in single-cellular organisms substances can diffuse directly into the cell across the cell surface membrane because of the small diffusion pathway so it’s efficient enough

• in multicellular organisms diffusion is too slow:
• diffusion pathway is too far as cells are deep within the body
• larger animals have low surface area: volume ratio so is difficult to exchange enough substances to supply a large volume through small surface
• higher metabolic rate, so use oxygen and glucose faster

Question 5

Explain how the root hair cell is adapted for exchange.

Answer 5

-Large surface area: have many hairs which each are covered in millions of microscopic hairs = rate of absorption of water and mineral ions is increased

Question 6

Explain how alveoli are adapted for gas exchange

Answer 6

• Thin: each alveolus is made from a single layer of thin, flat cells (alveolus epithelium) = short diffusion pathway to which oxygen and carbon dioxide diffusion takes place, which increases rate of diffusion
• Good blood supply: alveoli surrounded by a large capillary network, giving each alveolus its own blood supply which takes away oxygen and brings more carbon dioxide
• Ventilation: lungs are ventilated so air is constantly replaced= maintains concentration gradient of oxygen and carbon dioxide
• Large surface area: large numbers of alveoli= increases possible surfaces for oxygen and carbon dioxide to diffuse across so more efficient

Question 7

Explain how fish gills are adapted for gas exchange (2 ways)

Answer 7

• large capillary network = keeps good supply of blood
• Well ventilated: fresh water constantly passes over the gills so oxygen concentration gradient is maintained = increases the rate at which oxygen diffuses into the blood

Question 8

Explain briefly how the lungs work as an exchange organ for mammals

Answer 8

• as you breathe in, air enters trachea
• trachea splits into 2 bronchi, one bronchus leading to each lung
• each bronchus then branches off into smaller tubes called bronchioles
• these bronchioles then end in small air scans called alveoli, where gases are exchanged
• the rib cage, intercostal muscles and diaphragm all work together to move air in and out

Question 9

For goblet cells, explain their function, and distribution in the gas exchange system.

Answer 9

• lining the airways, they secrete mucus. The mucus traps microorganisms and dust particles in the inhaled air, stopping them from reaching the alveoli
• found in trachea, bronchus and bronchioles

Question 10

For ciliated epithelium, explain their function, and distribution in the gas exchange system.

Answer 10

• produces a synchronised movement which wafts the mucus upwards away from the alveoli towards the throat where it’s swallowed, to keep the lungs clean and prevent infection
• lines trachea, bronchus and bronchioles

Question 11

For elastic fibres, explain their function, and distribution in the gas exchange system.

Answer 11

• help the process of breathing out. On breathing in the lungs inflate and the elastic fibres are stretched, then the fibres recoil to help push the air out when exhaling
• found in the walls of the trachea, bronchi, bronchioles, and alveoli

Question 12

For smooth muscle, explain their function, and distribution in the gas exchange system.

Answer 12

• controls diameter of parts of gas exchange system. During exercise the smooth muscle relaxes, making the tubes wider, so there’s less resistance to airflow and air can move in and out of the lungs more easily.
• found in walls of trachea, bronchi and bronchioles

Question 13

For cartilage, explain their function, and distribution in the gas exchange system.

Answer 13

• it provides support, strong but flexible it stops the trachea and bronchi collapsing when you breathe in and the pressure drops
• found in walls of trachea and bronchi

Question 14

For squamous epithelium, explain their function, and distribution in the gas exchange system.

Answer 14

• it’s one cell thick to give a short diffusion pathway for gas exchange
• alveoli