transport Flashcards
why can unicellular organisms rely on diffusion for movement of substances?
they have a large surface area to volume ratio so nutrients and other substances can pass into their cell quickly and easily.
why do large multicellular organisms need transport systems?
they have a small surface area to volume ratio and therefore cannot rely on diffusion of substances as this would take too long and would not provide enough of the necessary nutrients needed.
what does the phloem transport and how?
the phloem moves sucrose and amino acids via translocation (in both directions)
what does the phloem consist of?
living cells arranged end to end.
the phloem enables movements between —– and —–.
sources (where substances are made or absorbed) and sinks (where substances are used or stored)
does translocation require energy?
yes, companion cells provide this energy.
state the function of the sieve plates in the phloem
allow for continuous movement of organic substances up and down the phloem
what does the xylem transport and how?
water and mineral ions via the transpiration stream (upwards only)
what does the xylem consist of?
elongated dead cells (no cytoplasm, impermeable to water, cell walls contain lignin) arranged end to end to form vessels
how are minerals and water absorbed by the root hair cells?
minerals are absorbed by active transport, water is absorbed by osmosis.
give two adaptations of root hair cells
large SA, contain many mitochondria.
what is transpiration?
the evaporation of water from the surface of a plant’s leaves through the stomata.
state and explain the effect of increasing light intensity on transpiration.
as light intensity increases, transpiration increases as the stomata open wider to allow more carbon dioxide into the leaf for photosynthesis.
describe the pathway of water from the soil to the leaves
soil -> root hair cells -> root cortex cells-> xylem -> leaf
describe the composition of blood
red blood cells, white blood cells, platelets and plasma
what is the role of the plasma?
transporting carbon dioxide, digested food, urea, hormones and heat energy