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Edexcel bio b unofficial mark scheme paper 3

percent was 776 ish percent
urea to chloride is 41
carrier chnace was 50
hardy weinberg was 3.92
urea made by nitrogen in amino acids converts to ammonia which is converts to urea
aseptic technique- ethanol disinfectant,closed windows, bunsen burner for updraught ,hold lid above at angle, flame loop and cool then get bacteria, open lid of tube at angle above,flame it then streak loop across, redo lid-heat to culture
loop of henle- descending limb freely permeable to water so diffuses out, fluid inside most conc,first part of upper permeable to ions so flow out,second part actively transported out so medullary conc very high,dct and collecting suct can reabsorb based on ADH conc and vary urine conc.
potato and carrot, cork borer to get tubes,scalpel and tiles and ruler to get 1 cm cube, weigh both and record. Prepare different concs of hypertonics solution from sucrose, place cubes in sucrose for same time, water bath to maintain temp. measure mass after and calc change mass, plot graph and stat test it, whichever veg has higher water potential will have a larger masss chnage as WP gradient is larger.
Add red dyed manometer fluid into tubes, idk i was waffling here, do one with glass beads and see how fluid moves-allows to correct other one for temp and pressure conditions- remove o2 for yeast condition,remove co2 absorber so co2 produced can affect volume and pressure and so fluid movement. add diff fluoride ion concs, same time for yeast, measure distance travelled for each and plot a graph, stat test T for significance
single celled organisms have a high sa:vol, short diff distance so all GE by diffusion
cut insect-http://www.nuffieldfoundation.org/practical-biology/dissection-ventilation-system-locust
glass used as poor heat conductor so wont trasnsfer heat to seeds,glass is transparent so far red light can be used to inhibit germination and poor transmission of humidity
ball was glomerulus, process was ultrafiltration
zika virus- mosquito nets to not transmit to others and to get into habit to try to eradicate diseases
diff countries have diff temp, humidity and light conditions, so need different control conditions and different seed conditions to limit germination.
in last Q, at shore high salt conc for high WP gradient so water travles in by osmosis, increases upshore as water salt content decreases to maintain same WP gradient
any other questions

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Original post by Dwarf-Shortage
percent was 776 ish percent
urea to chloride is 41
carrier chnace was 50
hardy weinberg was 3.92
urea made by nitrogen in amino acids converts to ammonia which is converts to urea
aseptic technique- ethanol disinfectant,closed windows, bunsen burner for updraught ,hold lid above at angle, flame loop and cool then get bacteria, open lid of tube at angle above,flame it then streak loop across, redo lid-heat to culture
loop of henle- descending limb freely permeable to water so diffuses out, fluid inside most conc,first part of upper permeable to ions so flow out,second part actively transported out so medullary conc very high,dct and collecting suct can reabsorb based on ADH conc and vary urine conc.
potato and carrot, cork borer to get tubes,scalpel and tiles and ruler to get 1 cm cube, weigh both and record. Prepare different concs of hypertonics solution from sucrose, place cubes in sucrose for same time, water bath to maintain temp. measure mass after and calc change mass, plot graph and stat test it, whichever veg has higher water potential will have a larger masss chnage as WP gradient is larger.
Add red dyed manometer fluid into tubes, idk i was waffling here, do one with glass beads and see how fluid moves-allows to correct other one for temp and pressure conditions- remove o2 for yeast condition,remove co2 absorber so co2 produced can affect volume and pressure and so fluid movement. add diff fluoride ion concs, same time for yeast, measure distance travelled for each and plot a graph, stat test T for significance
single celled organisms have a high sa:vol, short diff distance so all GE by diffusion
cut insect-http://www.nuffieldfoundation.org/practical-biology/dissection-ventilation-system-locust
glass used as poor heat conductor so wont trasnsfer heat to seeds,glass is transparent so far red light can be used to inhibit germination and poor transmission of humidity
ball was glomerulus, process was ultrafiltration
zika virus- mosquito nets to not transmit to others and to get into habit to try to eradicate diseases
diff countries have diff temp, humidity and light conditions, so need different control conditions and different seed conditions to limit germination.
in last Q, at shore high salt conc for high WP gradient so water travles in by osmosis, increases upshore as water salt content decreases to maintain same WP gradient
any other questions


last question was on adaptations i worte pointly leaves to limit water loss from transpiration as distance increases from shore(since lower water levels)
What did you put for the question about why red light was used? It was the experiment on ethanol one
Original post by Ottomanjanissary
last question was on adaptations i worte pointly leaves to limit water loss from transpiration as distance increases from shore(since lower water levels)


Sounds good-that's probably the 3rd mark i didn't mention that
Reply 4
i think there was a third mark for something to do with the picture for the last question? I wrote lack of leaves so low transpiration

wasn't the question about glass as a container to do with analysing the data? :s-smilie:
(edited 6 years ago)
Original post by Arnaez4
i think there was a third mark for something to do with the picture for the last question? I wrote lack of leaves so low transpiration

wasn't the question about glass as a container to do with analysing the data? :s-smilie:

Yeah I did describe the graph etc and a bit and added above
Original post by teenhorrorstory
What did you put for the question about why red light was used? It was the experiment on ethanol one


Idk I waffled so badly I said contrast is better, more easily absorb green light I don't even think I got any marks here
Reply 7
what units did oyu guys put for the rate of change for cellophone? I was confused af and put % month ^-1
Original post by Arnaez4
what units did oyu guys put for the rate of change for cellophone? I was confused af and put % month ^-1


I said about 3 a month or 37 a year I put both
Reply 9
oh and i got 140500 or something for clover leafs

and mucus salt solution Q anyone? I put 0.7% same water potential as mucus, 7.0% lower water potention so water diffuses in via osmosis
(edited 6 years ago)
Original post by teenhorrorstory
What did you put for the question about why red light was used? It was the experiment on ethanol one


i said red light was used coz green leaf meant absorption peak is red light- absorbs it well. idk iof right but then also wrote about red light and Pfr formation . waffle upon waffle literally worte everyhting i knew about red light :s-smilie:
Original post by Arnaez4
what units did oyu guys put for the rate of change for cellophone? I was confused af and put % month ^-1


think i got 8.6 per month or something like that wbu
Original post by Arnaez4
oh and i got 140500 or something for clover leafs

and mucus salt solution Q anyone? I put 0.7% same water potential as mucus, 7.0% lower water potention so water diffuses in via osmosis


i said 0.7 % to compare high dose because then we can see how more salt can alleviate cystic fibrosis
Original post by Arnaez4
oh and i got 140500 or something for clover leafs

and mucus salt solution Q anyone? I put 0.7% same water potential as mucus, 7.0% lower water potention so water diffuses in via osmosis

Same for clover leafs.similar for other one and added how normal people have some salt in their diet or something idk I just wanted to fill up the lines but I said what you said .
Reply 14
thoughts on total mark grade boundaries then? if last year's A was 55%, maybe it's reasonable to expect 65% A*? but that's 195/300, sounds really low :|
Original post by Arnaez4
thoughts on total mark grade boundaries then? if last year's A was 55%, maybe it's reasonable to expect 65% A*? but that's 195/300, sounds really low :|

I think an A* would be around 65% as well, and an A between 50-55%

60% or around that was an A* on last year's A level paper
Original post by Arnaez4
thoughts on total mark grade boundaries then? if last year's A was 55%, maybe it's reasonable to expect 65% A*? but that's 195/300, sounds really low :|


plz feel free to comment on my answers/correct them :smile:

first question, penicillin was most common, we have wide variety of antibiotics as research develops, used datas explained general points like how resistance limits variety of antibiotics today etc.
percentage 773 something like that
urea to chloride (or was it calcium?), done percentage change think I got 40 something
recessive cystic fibrosis 50% chance crossed Cc with cc
skipped hardy Weinberg
aseptic techniques- sterilise inoculating loop by Bunsen burner, disinfect surface via ethanoic disinfectant, remove sterilised cotton wool from flask containing broth, quickly inoculate, quickly put wool back in. nutrient agar must always be sterelised by shake and incubate at 25 or below to avoid pathogens to infect humans etc talked about other sterilising techniques too
loop of henle- wrote everything I knew about it e.g descending and ascending limb, water potential in the medulla as it descends lower, water diffuses out, ion diffusion , then said at low water levels/potential more ADH is produced by pituitary gland which opens up the collecting duct and water diffuses to the surrounding inc loop of henle and urine is more concentrated and less watery.
Why no glucose- reabsorbed by blood in PCT
Single cells- lower demand for oxygen, not as active as other multicellulars, and high SA;V ratio
Locus- cut along abdomen carefulnot to cut trachea. Stain tracheoles and view under microscope
Air ducts- main site of GE. Also can pump air in during mechanical ventilation. Never heard about these but I think u had to say SA;V. fk I fotgot to say
Problem with breathing rate conclusion, 1 locust, no time lag between addition of pure oxygen, gender of locust, 1 measure taken, mean should be taken from multiple measurments,other factors may affect breathing rate
Metal not used as expenisve, cellophane and paper poor germination rate most cells die, glass easy to regulate,observe used data etc
red light used= abosrption peak for green leaf, abosrbs well, Pr to Pfr.
at 0 some red light was already being absorbed due to pigments
50 used to be respresentative. If 1 used. Not indicative
Bowman capsule inside: glomerulus process- ultrafilitration
Zika virus- mosquite can bite u and infect someone else, protect other people in ur house can make symptoms worse, complex life cycle can infect others.
Different countries have different condiqotions/requirments to germinate. E.g countries near equator have high temp requirement, light etc
Mucus more watery, lower WP than salt solution. Water from salt solution osmosis to mucus more watery.
Potato and carrot- set up diff concentrations of sucrose solutions, put nknown mass of each each tissue for set time, measure mass at time intervas e.g after every 5 mins using weighing boat. Ass sucrose increase, water out of tissue= less mass. Student t test to compare values. Potatoto storage has chitin- slower release of water. Plot graph time(x), mass change(y) 2 sperate curves- compare each one. Measure the the sucrose concentration after tissue taken out- more dilute= water entred into it from tissue etc etc
9 marker completely failed. Said use ions in syringe and control movement of it via 3 way tapcould measure production of ethanol, yeast instead of woodlice, meaure air bubble movement at different con of ions. Literally all I said. Left so many lines blank. Plot graph
Last question, adapted by having pointy leaves which smaller SA;V ratio so less trsnspiration. Also lare SA;V of roots increasing water uptake
How to measure abiotic factor- light probe-measure light intensity electronically by abosribing wavelengths of light and calculating a value

Correct any worng ones plz J any more questions?
Reply 17
**** did you need to vary sucrose solution for the potato/carrot? I just picked one, repeat multiple times, perform a t test
Original post by srepse
**** did you need to vary sucrose solution for the potato/carrot? I just picked one, repeat multiple times, perform a t test


yeah I only did one concentration. That concentration will allow you to see whether there is a % increase or decrease so is enough to determine water potential. If ones mass increases more than the other at a given concentration, then it has a lower water potential than the other vegetable
Fml I ****ed up the water potential experiment question. I correctly talked about using cork borer to cut tissues and cutting them thin, measuring mass before and after, repeats, drawing of graph etc, but I didn't talk about making different sucrose concentrations. I just said place the tissue in water lol. How many marks would I lose?

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