Topic 8: Exchange & Transport Flashcards
What are the 6 materials that are exchanged in our body?
- Oxygen
- Dissolves food molecules
- Mineral ions
- Water
- Carbon dioxide
- Urea
How to calculate SA:vol ratio?
SA/volume
What SA:vol ratio does a single celled organism have? Why?
Large ratio
SO substances can diffuse in and out at a high rate and easily reach all parts of the cell
What SA:vol ratio does a multicellular organism have? What is the result of this?
Small ratio - many cells are too far away from the outer surface to get substances in and out this way larger
SO they need specialised exchange surfaces where substances can enter and leave the transport system by diffusion e.g. lungs in mammals - these are adapted to increase their surface area to maximise the rate of diffusion
Why are exchange surfaces and transport systems important?
So needs of every cell can be met
What 3 factors affect the rate of diffusion?
Distance - short distance increases rate of diffusion
Concentration gradient - high concentration gradient increases rate of diffusion
Surface area - large surface area increases rate of diffusion
What is Fick’s law?
Rate of diffusion ∝ (surface area x concentration difference) ÷ thickness of membrane
What has to happen to the factors for rate of diffusion to double?
If surface area or difference in concentration doubles
OR
If thickness of membrane halves
Where does gas exchange take place?
In the alveoli (which are in the lungs)
What does the alveoli look like?
Like a ball with a capillary around it
What happens in the alveoli that creates gas exchange?
CO2 goes into the alveoli from the blood cells in the capillary
O2 from the alveoli goes into the blood cells that are in the capillary
What are the adaptations of the alveoli that allow for gas exchange?
- Big surface area - so a large volumes of the gases can diffuse at once
- Thin walls - so there’s a short diffusion distance
- Good blood supply from the capillary - maintains the CO2 and O2 concentration gradients
- Moist lining - so that the gases can dissolve
What are the four components of the blood?
- Red blood cells (erythrocytes)
- White blood cells
- Platelets
- Plasma
What is the function of the red blood cells?
To carry oxygen around the body
Description/adaptations of the red blood cells?
No nucleus - more room for O2
Contains haemoglobin - binds to O2
Biconcave shape - large surface area so lots of O2 absorbed
What is the function of the white blood cells?
Defends against infection
Phagocytes: engulf and destroy pathogens
Lymphocytes: produces antibodies (attacks pathogens)
Description/adaptations of the white blood cells?
Lymphocytes - have antitoxins and antibodies on their surface
Phagocytes - have an opening where the pathogen is engulfed
What is the function of the platelets?
Help the blood to clot at a wound
Description/adaptations of the platelets?
Are made of fragments of cells
What is the function of the plasma?
Carry everything in the blood