Exchange And Transport Flashcards
What materials need to be exchanged between organisms and the environment?
- respiratory gases
- excretory products
- heat
Give examples of passive exchange processes
Osmosis, diffusion, facilitated diffusion
Give features of an exchange surface
- large SA to volume ratio
- short pathway for diffusion
- movement of internal and external medium to maintain gradient
- partially permeable
What is the equation for rate of diffusion?
SA x diff in conc
Length of pathway
Describe gas exchange in single-called organisms
They are small, so have a large SA to volume ratio. Gases can be exchanged across body surface, which is just a cell-surface membrane (is partially permeable)
What adaptations to insects have to limit water loss?
- waterproof covering
- small surface area to volume ratio
Describe route of gases within an insect
Gases enter and leave through spiracles on body surface,then enter internal network of tracheae. Tracheae branch into trachioles that penetrate into tissues.
How do gases move in and out of an insect?
- along a diffusion gradient; at end of trachioles there is high conc of CO2 and low conc of O2, gases diffuse
- ventilation; movement of air is accelerated by compression and expansion of abdominal muscles
Explain why a fish’s body surface is not suitable for direct gas exchange
Fish have a waterproof, gas-tight outer covering, and a small SA;volume ratio. Therefore a specialised internal exchange surface is required; the gills.
What is the purpose of lamellae on gill filaments?
Increase SA
What is countercurrent exchange?
Describes how blood flow in gills is in opposite direction to flow of water; this way there is always more O2 in water, so equilibrium is never reached and diffusion is constant
How are leaves adapted for rapid diffusion of gases?
- thin and flat; large SA to volume ratio
- many stomata (especially on underside)
- numerous air spaces throughout mesophyll
How do plants control the rate of gaseous exchange in leaves?
Guard cells open and close stoma; water loss is balanced with need of gases
Why do large organisms need a transport system for gas exchange?
SA to volume decreases with increasing size, needs cannot be fulfilled by body surface alone. Exchange system is needed to absorb nutrients and gases, transport system is required to move materials to cells and back to exchange surface.
Give some features of transport systems
- suitable medium in which to carry materials
- closed system of vessels
- mechanism for moving materials (animals use muscular contraction or heart, plants rely on transpiration pull)
- mechanism to maintain flow in 1 direction (valves)
- way of controlling flow
Why is the transport system in mammals referred to as ‘double circulatory system’?
Blood passes through the heart twice for each complete circuit of the body
What are the 5 layers of arteries, arterioles and veins?
- tough outer layer; resists pressure changes
- muscle layer; contracts and controls flow
- elastic layer; maintains pressure by stretching and recoiling
- thin inner lining; prevents friction
- lumen; central cavity
Why is the elastic layer of arteries relatively thick compared to veins?
Blood pressure has to remain high for blood to reach extremities; elastic stretches with each beat of heart and springs back in diastole, maintaining high pressure
Which has a thicker muscle layer and why; arteries or arterioles?
Arterioles; contraction of muscle layer allows constriction of lumen, and therefore controls blood flow into capillaries
What is the function of valves in veins?
To prevent backflow and pooling
How are capillaries adapted for their function?
- walls are 1 cell thick; short diffusion pathway
- narrow lumen; red blood cells are squeezed flat, reduces diff pathway
- numerous and highly branched; large SA
- permeate tissues
What is tissue fluid?
A watery liquid containing glucose, amino acids, fatty acids, salts and oxygen. Bathes all cells, giving nutrients to cells and receiving CO2 and waste materials in return.
Describe how tissue fluid is removed and returned to blood
- at arteriol end of capillaries, hydrostatic pressure is produced by pressure of blood moving through narrower vessels. Pressure only pushes out tissue fluid-ultrafiltration
- at venule end, hydrostatic pressure is higher in tissue fluid outside of blood, tissue fluid is returned. Osmotic forces pull water back in.
How are the contents of the lymphatic system moved?
- hydrostatic pressure of tissue fluid that has left capillaries
- muscle contraction
