Exchange Surfaces Flashcards
What is an exchange surface?
- A specialised area that is adapted to make it easier for molecules to cross from one side of the surface to the other
How does a large surface area help efficiency?
- More space for molecules to diffuse
How does a thin barrier help efficiency?
- Short diffusion distance
How does a permeable membrane help efficiency?
- Allows desired molecules through
How does a good blood supply help efficiency?
- Keeps concentration high so diffusion gradient is high
How does ventilation help efficiency?
- Maintains diffusion gradients of gases by bringing/removing 02 and CO2
Explain the adaptions and functions of the small intestine
Adaptions:
- Villi are 1 cell thick so allows short diffusion distance
- Network of blood capillaries in each villi to maximise amount of exchange
Functions:
- Rich blood supply to allow absorption to take place efficiently
- Villi 1 cell thick so digested nutrients can cross walls to reach blood capillaries
What are microvilli?
- Located on surface of epithelial cells
- Increase surface area of small intestine
- Good at absorption of nutrients
Explain the adaptions and functions of the liver
Adaptions:
- Hepatocytes are main liver cells
- Spaces between hepatocytes increases amount of 02
Functions:
- Produces bile which breaks down fats in small intestine
- Regulates blood levels of amino acids
- Absorbs nutrients
- Receives O blood from heart via hepatic artery
- Receives D blood from hepatic portal vein
Explain the adaptions and functions of the alveoli
Adaptions:
- Good blood supply, network of capillaries
- Large surface area
- Thin wall layers, 1 epithelial cell thick
- Elastic recoil, tissues stretch as air enters and return back to normal, helps squeeze air out
Functions:
- Moves O2 and CO2 molecules in&out of bloodstream
- Large SA helps increase rate of gas exchange
- Capillaries close to walls = short diffusion distance
Why is the lining of alveoli moist?
- Allows gases to dissolve which allows them to diffuse at a faster rate
Explain the adaptions and functions of root hair
Adaptations:
- Large SA beneficial in water and nutrient absorption in soil
- Thin surface layer so diffusion and osmosis take place quick
- Large structures to take up mineral ions and water from soil
Functions:
- Small sizes so can penetrate easily between soil particles
- Large amounts of mitochondria releases energy from glucose in respiration to provide energy needed for AT
Explain the adaptions and functions of hyphae
Adaptations:
- Large network
- Firm cell wall
- Cross wall structures called septa dividing hyphae into compartments
Functions:
- Feathery filaments making up multicellular fungi
- Release enzymes and absorb nutrients from food source
- Branches out and creates large network called mycelium
Why do large, active organisms need special surfaces for exchange?
- Large animals have a small SA:Vol
- Means there is not enough surface to provide many of the central cells with the supplies they need as the distance the substances need to travel is too great
- The more active the organism, the more supplies and waste products will need to be transported
Name the air sacs and why there are many air sacs in the lungs
- They are called alveoli and they have a large SA for diffusion
Name the type of epithelium in the walls of the air sacs
- Flattened epithelium
Air sacs contain many elastic fibres
Explain the role of these elastic fibres during ventilation
- Enables the air sacs to expand and return to their original shape as they recoil which allows air to be squeezed out
- Prevents alveoli from bursting
Explain how refreshing the air in the air sacs helps to maintain a steep diffusion gradient
- Alveoli has lots of oxygen supply met with deoxygenated blood
Explain inhalation (inspiration)
- External intercostal muscles contract to raise rib cage
- Diaphragm contracts to become flatter pushing digestive organs down
- Volume of chest cavity increases
- Pressure of thorax decreases
- Air moves into lungs
Explain exhalation (expiration)
- External intercostal muscles relax and ribs fall
- Diaphragm relaxes and is pushed up by displaces organs underneath
- Volume of chest cavity decreases
- Pressure in lungs and thorax increases
- Air moves out of lungs
How are 2 opposing concentrations gradients maintained?
- Ventilation replenishes needed oxygen and gets rid of waste CO2
- This ensures conc gradients are maintained so that these gases moves
- Blood transports both o2 and CO2 separate so both can move at once
What is a spirometer? How does it work?
- Airtight oxygen-filled chamber
- As person breathes in and out, the lid moves up and down
- Chamber gas volume decreases with time
- Any Co2 is breathed out by soda lime