4.4 Flashcards
what are three principles plants use to build tall structures?
1) produce strong cell walls out of cellulose
2) build columns and cells from specialised cells
3) strengthen cells with lignin
what is plarenchyma?
a type of plant tissue found throughout the plant which fills spaces between more specialised tissues
what is cellulose made from?
beta glucose units
what is the bond between the glucose molecules in cellulose?
1,4 glycosidic bond
how are microfibrils formed?
hydrogen bonds form between the OH groups in neighbouring cellulose chains
what is the glue that holds the microfibrils together?
branched polysaccharides called hemicelluloses and pectins
where else are pectins found?
in the middle lamella (the region between the cell walls of adjacent cells)
what are the plasmadesmata?
narrow fluid filled channels that cross the cell walls
what do xylem vessels transport?
water and minerals
what do phloem sieve tubes transport?
organic solutes
from the inside to the outside of the vascular bundle, what are the three elements?
xylem, phloem and sclerenchyma fibres
what does lignin to in the xylem vessels?
it impregnates the cell wall and the entry of water and solutes into them is restricted
what happens during autolysis?
the cell organelles, cytoplasm and cell surface membrane are broken down by the action of enzymes and are lost leaving dead empty cells that form a tube
what happens in the xylem?
transpiration
what happens in the phloem?
translocation
what three cells surround the phloem sieve tubes?
transfer cells, companion cells and phloem plarenchyma cells
what are the processes that extract plant fibres called?
retting
how to bacteria produce and what happens?
binary fusion: the circular dna replicates and new cell content is synthesised before the new cell wall forms to divide the cell into two roughly equal halves
what three conditions are needed for successful bacterial growth?
sufficient nutrients, optimum temperature and no build up of toxic waste products
who did the first drug trial investigating digitalis?
william withering
what two things did withering do in his trial?
tested unhealthy patients to record side effects and discover the correct dosage
what does pre-clinical testing involve?
laboratory studies are carried out on isolated cells and tissue cultures to assess safety and determine whether the compound is effective
what does the clinical trials phase 1 involve?
healthy volunteers are given different doses of which the side effects are monitored
what does the clinical trials phase 2 involve?
small groups of patient volunteers are treated to look at the drugs effectiveness
what does the clinical trials phase 3 involve?
two large groups of patients are split into two, half are given the drug and the rest a placebo (double blind randomised controlled trial)
