weaknesses Flashcards
(11 cards)
polygenic
characteristic which shows continuous variation
caused by multiple genes at different loci
explain how epigenetic changes affect development of tissue in an embryo
dna in a chromosome is wrapped around a histone
acetylation affects binding of tRNA polymerase
methylation affects transcription of mRNA
gene expression altered
division of stem cells/ how they become specialised
chemical signals/ stimuli cause some genes to be activated/ switched on
only activated genes are transcribed
mRNA produced and translated so protein is produced
proteins determine structure and function of cell
respiratory minute volume
volume of air that can be breathed in/ out in a minute = tidal volume x ventilation rate
find the difference in peak to trough volume to give tidal volume
find ventilation rate
multiply them
oxygen consumption
difference in volume of one peak compared with a subsequent one
divide time between troughs and multiply by 60
why is outer mitochondrial membrane impermeable to H+
stops H+ diffusing out of mitochondrion into cytoplasm
maintains high H+ conc in intermembrane space
so H+ can move down concentration gradient by chemiosmosis to synthesise ATP
role of carrier molecules in ETC
receive hydrogen from reduced NAD/ FAD to allow NAD to be oxidised
break hydrogen into protons/ H+ and electrons
electrons transferred along carrier molecules by series of redox reactions
energy released is used to pump H+ into intermembrane space
gene expression
genes can be activated/ deactivated
if cells receive same stimulus, same gene will be switched on/ activated
results in production of same protein/ enzyme
development/ organisation of axons in eye
ocular dominance columns develop in visual cortex
neurones form synapses with those cells/ columns
stimuli/ action potentials along neurones strengthen connection with cells of ocular dominance columns
stimulation during critical period is required to form effective connections in the visual cortex
role of sodium ions in rod cell
sodium ions are pumped out of the inner segment
in the light (when stimulated), sodium ions do not move back into rod cell
in the dark (when unstimulated), sodium ions can move back into rod cell
in the light, rod cell is hyperpolarised
in the dark, rod cell is depolarised
effect of light intensity on eye
increased light intensity causes rhodopsin to be broken down so opsin is released
therefore more opsin binds to channel proteins in outer segment
sodium voltage gated channels close
reduces influx of sodium ions by making membrane impermeable to sodium ions
