topic 10 - human transport Flashcards
why do unicellular organisms rely on diffusion?
When the surface area to volume ratio is large, there is a lot of surface area for diffusion and not much volume to travel within. which is why unicellular organisms rely on diffusion alone to get the substances they need.
why are transport systems needed in multicellular organisms?
multicellular organisms contain many layers of cells, meaning that the distance between the surface of the organism to its centre is relatively long. the diffusion distance is too great to rely on diffusion alone as it cannot occur at a sufficient rate to meet the needs of the organism, so larger organisms usually have transport systems, which is the circulatory system for humans.
components of blood
red blood cells, white blood cells, platelets and plasma
% of each component of blood
45% red blood cells, 55% plasma, less than 1% platelets and white blood cells.
structure of red blood cell
- biconcave
- no nucleus
- plenty of protein haemoglobin
structure of white blood cell
- large cell
- big nucleus
- all are slightly different
structure of platelet
fragments of cells
structure of plasma
straw coloured liquid
role of plasma in transporting CO2
CO2 is dissolved in the plasma as hydrogencarbonate ions and transported from respiring cells to the lungs
role of plasma in transporting digested food
the dissolved particles are absorbed from the small intestine and delivered to requiring cells around the body
role of plasma in transporting urea
Urea is the waste substance produced in the breakdown of proteins by the liver. Urea is dissolved in the plasma and transported to the kidneys
role of plasma in transporting hormones
hormones are released into the blood from the endocrine organs (glands) and delivered to target tissues/organs of the body
role of plasma in transporting heat energy
heat energy is transferred to cooler parts of the body or to the skin where heat can be lost
3 adaptations of red blood cells and how they help the transport of oxygen
- full of haemoglobin, a protein that binds to oxygen to form oxyhaemoglobin
- no nucleus which allows more space for haemoglobin to be packed in
- ‘biconcave disc, allowing them a large surface area to volume ratio to maximise diffusion of oxygen in and out
2 types of white blood cells
phagocytes and lymphocytes