Module 3 Section 1 - Specialised Exchange Surfaces Flashcards
What do organisms need to do with their environment
They need to exchange substances
What do cells need to take in
Things like oxygen and glucose for aerobic respiration and other metabolic reactions
What do cells need to excrete
Waste products from metabolic reactions e.g. carbon dioxide and urea
What decides how easily the exchange of substances is
The organism’s surface area to volume ratio
Multicellular organisms need….
Exchange surfaces
In singled celled organisms substances such as glucose and oxygen can…
Diffuse directly into or out of the cell across the cell surface membrane
Why is the diffusion rate quick in single celled organisms
Because there is a short distance that the substance have to travel
Why is diffusion across the outer membrane of multicellular animals too slow
-some cells are deep within the body, big distance between the cell and outside environment
-larger animals have a low surface area to volume ratio, difficult to exchange enough substances to supply a large volume animal through a relatively small outer surface
-multicellular organism have a higher metabolic rate meaning glucose and oxygen is used up fast
What specialised features do exchange surfaces have to improve their efficiency
-Large Surface area
-Thin layers
-Good blood supply and/or ventilation
Give an example of an exchange surface with a large surface area
Root hair cells
What gives plant roots a large surface area
The cells on the plant roots grow into long hairs which stick out into the soil
What is the benefit of having the root hair cells
Gives the roots a large surface area which helps to increase the rate of absorption of water (by osmosis) and mineral ions (by active transport) from the soil
Give an example of an exchange surface which is thin
The alveoli
The alveoli is the site of what
Gaseous exchange in the lungs
What is the alveolus made of
A single layer of thin flat cells called alveolar epithelium
What diffuses out of the alveolar space in gaseous exchange
O2 diffuse out of the alveolar space into the blood. CO2 diffuses in the opposite direction
How does the alveolar epithelium increase the rate of diffusion
The alveolar epithelium is thin this decreases the distance over which O2 and CO2 diffusion takes place
Give examples of exchange surfaces which have good blood supply and/or ventilation
Alveoli
Fish gills
How are the alveoli adapted to have a good blood supply
Each alveolus has its own blood supply because they are surrounded by a large capillary network this helps to bring a steep concentration gradient as the blood takes O2 away and brings CO2
How are the alveoli adapted to have a good ventilation
The air in the alveoli is constantly being replaced every time you breathe in and out this helps to maintain a steep concentration gradient
How are fish gills adapt to have a good blood supply
They contain a large network of capillaries meaning O2 and CO2 are constantly being exchanged which maintains a steep concentration gradient
How are fish gills adapted to have good ventilation
Fresh water is constantly being passed over them - this brings a steep concentration gradient
