exchange surfaces Flashcards
Why do organisms need specialized exchange surfaces?
Diffusion across the outer membrane is too slow, as cells are too far into the body, larger animals have a larger SA/V ratio and they have a larger metabolic rate than single celled organisms.
Why is it hard for larger organisms to exchange enough substances?
There is a greater need for substances in larger animals and they use them up much faster.
Describe single celled organism diffusion.
They can diffuse directly into and out of the cell surface membrane as the diffusion rate is fast due to the small distance the substances need to travel
What are three examples of adaptations exchange surfaces have to improve their efficiency?
Large surface areas, thin diffusion distances and a good blood supply/ventilation.
Describe an example of an exchange surface with a large surface area
Root Hair Cells - The cells on plant roots grow long hairs which stick out into the soil and each branch of a root is covered in millions of microscopic hairs giving it a large surface area increasing the rate of absorption of water by osmosis and mineral ions by active transport.
Describe an example of an exchange surface with a thin diffusion distance
The alveoli - the alveoli are the gas exchange surface in the lungs and each alveolus is made from a single layer of thin flat cells called alveolar epithelium. O2 diffuses out into the blood and CO2 diffuses in. The thin alveolar epithelium helps to decrease the distance over which diffusion takes place, increasing the rate
Describe a fish gills good ventilation
Fish gills are the gas exchange surface in fish, CO2 and O2 are exchanged between the fish’s blood and the surrounding water. Fish gills also have a large network of capillaries which keeps them well supplied with blood. They are also well ventilated as fresh water constantly flows over them which helps to maintain a concentration gradient.
What are the two examples of exchange surfaces with good ventilation and good blood supply?
Fish gills and Alveoli.
Describe the alveoli’s good blood supply and ventilation.
The alveoli are surrounded b a large capillary network which gives each alveolus its own blood supply. This allows it to constantly take oxygen away and bring in more carbon dioxide . The lungs are also well ventilated so the air in each alveolus is constantly being replaced which helps to maintain the concentration gradient.
What are the main mammalian gaseous exchange organs?
The lungs
How do the lungs exchange gasses
As you breathe in, air enters the trachea and then splits into two bronchi - one bronchus leading to each lung. Each bronchus splits off into smaller tubes called bronchioles and these end in small air sacs called the alveoli where gasses are exchanged.
What also helps the lungs exchange gasses?
The ribcage, intercostal muscles and diagram.
Where is cartilage found?
The walls of the trachea and bronchi
What does cartilage do?
It provides support - its strong but flexible and stops the trachea and bronchi collapsing when you breathe in and the pressure drops.
Where is ciliated epithelium found?
In the trachea, bronchi, larger bronchioles and smaller bronchioles.
What does ciliated epithelium do?
Its found in the linings of the airways and beats mucus moving it upwards and away from the alveoli towards the throat where it can be swallowed. This helps to prevent lung infections.
Where are goblet cells found?
Goblet cells are found in the trachea, bronchi and larger bronchioles.
What do goblet cells do?
They line the airways and secrete mucus, the mucus traps microorganisms and dust particles in the inhaled air stopping them from reaching the alveoli.
