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section K: TRANSPORT SYSTEMS (plants (root hair cells (take in water, each…
section K: TRANSPORT SYSTEMS
unicellular organisms can rely on diffusion or movement of substances in and out of the cell
diffuse directly into and out of cell membrane
diffusion rate quick because of short distance substances have to travel
Transpiration
= the evaporation of water from the surface of a plant and the vast majority of that is lost through the stomata
plants
xylem
carry water and mineral salts from the roots up the shoot to the leaves in transpiration stream
phloem
paper 2
root hair cells
take in water
each branch of a root will be covered in millions of these microscopic hairs
the cells on plant roots grow into long 'hairs' which stick out the soil
this gives the plant a big surface area for absorbing water from the soil
water is taken up by osmosis. usually a higher concentration of water in the soil than there is inside the plant, so the water is drawn into the root hair cell by osmosis
Why the need for transport?
large organisms have a small surface area to volume ratio
animals
blood vessels
artery
vein
capillaries
heart
insert heart diagram
right atrium gets deoxygenated blood from body through vena cava
deoxygenated blood moves through right ventricle which pumps it to the lungs (via pulmonary vein)
left atrium gets oxygenated blood from lungs (from pulmonary vein)
oxygenated blood then moves through left ventricle into , which pumps it out round the whole body (via aorta)
left ventricle has a much thicker wall than right. needs more muscle to pump blood round whole body, whereas right ventricle only pump to lungs. also means blood in left ventricle under higher pressure than right ventricle
the valves prevent the backflow of blood
exercise increase heart rate
-exercise increases amount of CO2 in blood
you need to get more oxygen into the cells and remove more CO2. Blood has to flow faster do heart rate increases. how:
-high levels of CO2 detected by receptors in aorta and carotid artery (in neck)
when you exercise your muscles need more energy so you respire more
-these receptors send signals to brain
-brain sends signals to heart, causing it to contract more frequently and with more force
hormonal system also control heart rate
when an organism is threatened (by predator) the adrenaline glands release adrenaline
adrenaline binds to specific receptors in the heart causing cardiac muscle to contract more frequently and more forcefully - heart rate increase and more blood pumped
this increases oxygen supply to the tissues, getting body for action
blood
cells
red blood cells
haemoglobin = carry oxygen
biconcave disc shape for large surface area
no nucleus for large surface area
platelets
enable blood clotting
need to avoid loss of blood & avoid pathogens causing infection
white blood cells
phagocytes
engulf/digest micro organisms
lymphocytes
release anti bodies
plasma (yellow fluid)
glucose
amino acids
hormones
heat
circulatory system
multicellular organisms need transport systems
need water, minerals, sugars and to expel waste
direct diffusion from outer surface would be too slow - substances would have to travel large distances to reach every single cell
multicellular organisms = plants and animals
so they need transport systems to move substances to and from quickly