Topic 8: Exchange and Transport in Animals Flashcards
What does the surface area to volume ratio tell us?
How easy it is for an organism to exchange substances with environment
Do single-celled organisms require exchange surfaces? - why?
No
- Gases can diffuse directly into (or out of) the cell across the cell membrane (because they have a large surface area to volume)
- So, enough substances can be exchanged across the membrane to supply the whole volume of the cell
Do multicellular organisms require exchange surfaces and mass transport systems? - why?
Yes
- Have a smaller surface area compares to their volume, making it difficult to exchange enough substances to supply their entire volume across their outside surface alone
What do multicellular organisms require when exchanging substances? (what do they do?)
Exchange surface - for efficient diffusion
Mass transport systems - move substances between the exchange substance and rest of the body
What does the rate of diffusion depend on?
Distance - substances diffuse faster when they haven’t got as far to move
Concentration gradient - substances diffuse faster if there’s a big difference in concentration from the area they are diffusion from and the area they are diffusing to
Surface area - the more surface area there is available for molecules to move across, the faster they can get from one side to the other
What’s the job of the lungs?
To transfer oxygen to the blood and to remove waste carbon dioxide from it
Where does gaseous exchange take place?
In the alveoli
Explain Gas Exchange
- The blood arriving at the alveoli has just come from the rest of the body, so it contains lots of carbon dioxide and not much oxygen
- This maximises the concentration gradient for the diffusion of both gases
- Oxygen in the alveoli diffuses out from an area of high concentration of O2 to low concentration of O2
- Carbon dioxide diffuses in the opposite direction to be breathed out
How are the alveoli specialised to maximise diffusion?
- Very thin walls, minimising the distance that the gases have to move
- Moist lining helps dissolve the gases
- Good blood supply to maintain the concentration gradients of O2 and CO2
- Enormous surface area
What does Fick’s Law represent?
Displays the relationship between the rate of diffusion and the factors that affects it
What’s Fick’s law?
Rate of diffusion is proportional to the surface area x concentration difference/thickness of the membrane
So, if the rate of diffusion doubles:
- Surface area and concentration difference will also double
- Thickness of membrane will halve
What do red blood cells do?
Carry oxygen from the lungs to all cells in the body
How are red blood cells adapted for their purpose?
- Biconcave disc shape gives them a large surface area to absorb oxygen
- Don’t have a nucleus which allows for more room to carry oxygen
- Contain red pigment called haemoglobin which contains iron
Explain what happens in the lungs and rest of the body regarding haemoglobin
In the lungs, haemoglobin binds to oxygen to become oxyhaemoglobin
In body tissues, oxyhaemoglobin splits up into haemoglobin and oxygen to release oxygen to the cells
What are Phagocytes?
White blood cells that can change shape to engulf unwelcome microorganisms (this is called phagocytosis)
What are Lymphocytes?
White blood cells that produce antibodies against microorganisms. Some also produce antitoxins to neutralise any toxins produced by the microorganisms
What happens, in terms of blood cells, when you have an infection?
White blood cells multiply to fight off the infection - so a blood test will show a high white blood cell count
