paper dos Flashcards
importance of maintaining glucose concentration
sufficient availability of respiratory substrate, stops water potential causing cells to burst or shrivel
role of negative feedback
restores systems to their original level
what creates a greater degree of control in feedback systems?
having separate systems to control different departures from the original state
how to explain action of hormones w blood glucode
‘activating enzymes involved in the conversion of…’
second messenger- what hormones trigger it and what enzyme does this activate
glucagon and adrenaline
adenylate cyclase
body parts involved in osmoregulation
hypothalamus and posterior pituitary gland
where is glucose reabsorbed in the kidney?
proximal convoluted tubule
process of glucose reabsorbtion
products such as glucose and amino acids are reabsorbed via co-transport with sodium ions through podocytes
which limbs of the loop of henle are permeable to what?
ascending- ions only
descending- water, ions also move in
net atp production from 1 krebs cycle
1 molecule
where do the electrons in the electron transfer chain come from?
reduced coenzymes
light-dependent reaction (5)
- chlorophyll absorbs light- it is photoionised
- some energy from photoionisation is conserved in the production of atp and nadph
- some atp is also produced from chemiosmosis, using energy from the electron transfer chain
- h+ are pumped into the thylakoid and catalyse atp synthase by moving out
- photolysis of water produces protons, electrons (which enter the etc) and oxygen
gpp definition
chemical energy store in plant biomass in a given area or volume
npp definition
chemical energy store in plant biomass after respiratory losses to the environment have been taken into account
net production of consumers
chemical store of ingested food - (faeces and urine + respiratory losses)
n = i - (f+r)
example unit of productivity
kJ ha-1 yr-1
nitrogen fixation
atmospheric nitrogen > ammonium ions, or other ammonium-containing products
nitrification
ammonium > nitrate via nitrite
denitrification
nitrate > atmospheric nitrogen
ammonification
breakdown of ammonium-containing products into ammonium ions
why is leaching bad
nitrates in water can cause problems with oxygen transport in babies, linked with increased risk of stomach cancer
eutrophication
- algal growth as nutrient availability no longer limiting, causing algal blooms
- less light at lower depths
- light becomes the limiting factor for plants and algae lower down
- dead plants and algae allow more growth of saprobiontic bacteria
- the bacteria use up the oxygen
- fish and other aerobic organisms die
why is eutrophication bad
populations of anaerobic organisms rise, and decompose the dead material, releasing more nitrates/other toxic material so water is bad
process that inhibit transcription
increased methylation
decreased acetylation
what is epigenetics?
heritable changes in gene function, without changes to the base sequence of dna
action of oestrogen
- easily diffuses through phospholipid bilayer
- binds with the receptor on a transcription factor
- dna binding site on transcription factor changes shape, now complementary to dna
- enters through nuclear pore and stimulates transcription of the gene
acetylation on transcription
- decreased makes the histones more positive
- so more attracted to phosphate groups on dna
- less accessible to transcription factors
methylation on transcription
- increased prevents binding of transcription factors
- induces deacetylation of histones
where do sirnas come from?
double stranded rna bound to an enzyme
what are schwann cells?
myelin-containing cells that provide electrical insulation/general protection
where is myelin?
in the cell membranes of schwann cells
open at resting potential
k+ channels, net movement of na+ out of pump
when do na+ channels close?
when +40mv potential has been established
what causes hyper-polarisation?
outward transport of k+ through the channels that are able to close
repolarisation
closable k+ channels shut, resting potential restored
name for the node of ranvier thing
saltatory conduction
greater axon diameter
increases speed of conductance due to less ion leakage
types of summation
spatial- multiple neurones
temporal- high frequency of neurotransmitter release from one neurone
3 purposes of the refractory period
one direction only
discrete impulses
limits number of action potentials
action of an inhibitory synapse
- neurotransmitter causes chloride ion channels to open
- cl- move in, also triggers k+ channels to open, so they move out
- membrane potential drops
- this hyperpolarisation makes it less likely that an action potential will be triggered
