Topic 8- Exchange And Transport In Animals Flashcards
What do cells need for aerobic respiration? What’s the waste product? How do they move?
Oxygen
Carbon dioxide
Diffusion
How’s water taken up by cells? What also moves with it?
Osmosis
Dissolved food molecules and mineral ions
Where and how is urea removed from the body?
It diffuses from cells to blood plasma for removal from body via kidneys.
What affects the ability to exchange substances with its environment?
Surface area to volume ratio
How does size affect surface area to volume ratio?
Larger = smaller surface area to volume ratio
How to calculate surface area to volume ratios
Represent the organism by a block.
Find its area then find its volume.
SA:V
simplify
How do single-celled organisms exchange substances?
Why?
Via direct diffusion into/ out of cell across membrane.
Have high surface area to volume ratio so enough substances can be exchanged to supply full cell volume.
How do multicellular organisms transport substances?
Have smaller SA:V so is hard to exchange enough to supply full cell volume from outside surface alone.
Need exchange surface (efficient diffusion) and a mass transport system to move between exchange surface and body.
Exchange surfaces are adapted to maximise effectiveness
Factors effecting rate of diffusion
DISTANCE- shorter diffusion pathway= quicker
CONCENTRATION GRADIENT- larger gradient = quicker diffusion
SURFACE AREA- more surface area= faster rate of reaction
Where does gas exchange in mammals occur?
Alveoli
Function of lungs
Transfer oxygen to blood and remove waste carbon dioxide.
Characteristics of blood arriving at alveoli
What happens to this blood?
Contains lots of CO2 and not much O2
*Maximises concentration gradient
Oxygen diffuses out of air in alveoli to blood (high to low) CO2 diffuses oppositely to be breathed out.
How are alveoli specialised to maximise diffusion of O2/CO2
Moist lining for dissolving of gases
Large blood supply maintaining gradients
V thin walls (shorter diffusion pathway)
Large surface area (more gas exchange to take place)
Fick’s law
Rate of diffusion (proportional to) surface area*concentration difference/ thickness of membrane
Function of erythrocytes
(Red blood cells)
Carry oxygen from lungs to cells in body
Adaptations of erythrocytes
Are biconcave so have a LARGE SURFACE AREA for absorbing oxygen.
Have NO NUCLEUS so therefore has more room to carry oxygen
Contain HAEMOGLOBIN (containing iron) which binds to oxygen to become oxyhemoglobin and then releases the oxygen at body cells
Function of white blood cells
Defence against infection
2 types of white blood cell
Phagocytes
Lymphocytes
Phagocytes function
Engulfment of unwelcome organisms (phagocytosis)
Lymphocytes function
Production of antibodies (and sometimes antitoxins which neutralise toxins produced by microorganisms) against microorganisms.
What blood test levels of white blood cells will you have when you have an infection?
High as white blood cells multiply during infection to fight it off
Platelets
Small fragments of cells w no nucleus.
Platelets function
Help blood to clot at a wound so blood levels aren’t lost and microorganisms Cant get in.
What can lack of platelets cause?
Excessive bleeding and bruising
Plasma
Pale liquid carrying everything in the blood.
What does plasma hold?
Red/white blood cells Platelets Nutrients (eg glucose/amino acids) (gut to cells) Carbon dioxide (organs to lungs) Urea (liver to kidneys) Hormones Proteins Antibodies/ antitoxins
3 types of blood vessel
Capillaries
Veins
Arteries