Biology Paper 2 Flashcards
What is epistasis?
When one allele masks another
What are the principles of epigenome?
Have tags that respond to environmental factors, chemical tags formed around DNA and histones so that it can be unwrapped to express active genes and determines the shape of the DNA histone complex, also ensures inactive genes are not read
What and why do they use the specific DNA polymerase in the thermocycler?
Thermophilic aquaticus and because it denatures at 95 degrees C so it does not denature
describe the phosphorus cycle
phosphates from rocks are eroded into oceans and running water that is absorbed by plants and excreted into the soil via death that then taken up by water to form new rocks
describe the light dependent reaction starting with Photolysis
chlorophyll absorbs light energy, excite electrons, move along carriers etc releasing energy, used to join ADP and pi to form ATP, photolysis of water produces protons electrons oxygen, NADP reduced by electrons
How is the gradient of sodium maintained in the loop of Henle?
Sodium diffuses out of ascending limb into interstitial space between ascending and descending, sodium moves into descending limb and water moves out of it into blood capillaries, thus as filtrate moves through loop of Henle it lowers its water potential until it reaches the bottom of the ascending limb that where sodium diffuses out and so water potential increases, then there’s a higher water potential gradient in the interstitial space between ascending and collecting duct so water moves out of collecting duct into blood vessels
what is biomass?
the dry weight of the total mass of living material in a specific area at a given time
What is glycogenesis?
Conversion of glucose to glycogen
three advantages of the structure of a chloroplast
contain both DNA and RNA so proteins can be manufactured quickly, thylakoid membrane has a large SA for rapid DF and a network of proteins in the Grana to maximise the absorbance of light
Describe the transmission across a cholinegenic synapse?
Calcium ions open because of AP that move into synaptic knob via FDF, this causes vesicles to fuse with the presynaptic neurone membrane that release acetylcholine into the synaptic cleft, acetylcholine then binds to protein receptors on the sodium ion channels on the post synaptic neurone that diffuse across a concentration gradient that causes a influx of sodium ions in the post synaptic neurone that causes an AP, acetylcholine then broken by acetylcholinerase into choline and Ethanoic acid and diffuses back across the synaptic cleft but does not cause an action potential in the pre synaptic neurone as it is not in its acetylcholine form
What are the functions of a synapse?
Combine multiple impulses at the same synapse so Brain is not overloaded with info + can stimulate multiple impulses in different neurones at the same time
three advantages of mesophyll in a leaf
air spaces between them = rapid diffusion, long and narrow and are packed with chloroplast the thin tissue of the leaf allows light to reach mesophyll
where does the light independent reaction
stroma in the fluid filled matrix
describe the electron transport chain
electron is oxidised that reduces NADP, carries out series of redox reactions along the electron transport chain that is then accepted by oxygen that is the terminal electron receptor which oxidises NADPH back to NADP
describe the process of the light independent reaction
CO2 combines 5 carbon ribulose-bi-phosphate to make 6 carbon molecule that is then catalysed by rubisco to create two 3 phosphate glycerate molecules that are then reduced via NADP and energy from ATP from LDR to triose phosphate that will eventually turn into glucose, NADP reformed and goes back to LDR
what is glycolysis and where does it happen?
phosphorylated glucose is broken down in two 3 carbon molecules called pyruvate. happens in the matrix mitochondria
what happens in the link reaction after Glycolysis?
pyruvate is decarboxylated and dehydrogenated to acetate NAD is reduced
what happens in the Krebs Cycle after the link reaction?
acetyl coenzyme A combines with oxaloacetate to form citrate which is decarboxylated and dehydrogenated to form 5 carbon molecule which is then dehydrogenated and decarboxylated to form 4 carbon ATP made by substrate-level phosphorylation and FAD is reduced, oxalacetate is then regenerated to restart the cycle
state where the Krebs cycle occurs
in the matrix of the mitochondria
explain the mechanism that allows ATP concentration to control the Krebs cycle
ATP binds away from the active site
causes the active site to change shape
can no longer bind to the substrate/cycle cannot continue as no substrate
less/no more ATP produced
describe how ammonium ion concentration increases in the soil when organisms die
protein/amino acids broken down by saprobionts
explain how Schwann cells help the neurone to carry out its function
insulates the axon only occurs at the node
allows faster transmission of impulse along axon
describe how the mark-release-recapture method could be used to estimate number of spawning age fish in the population
capture and count
carefully mark to avoid detection by predators
recapture, count marked and unmarked
describe genetic diversity
the variation of different alleles within a species
