OCR A2 Biology planning exercise!

cksjohns

That's the dilemma I'm currently facing.

Need to know how much aspirin in grams is in 10cm3 of a 1.5% solution of aspirin.

Having given up chemistry after AS i've forgotten all those formulae with mass/conc/volume ...moles...molar mass (!!??) which I guess could be used, anyone help me out?

Why not hunt down the AS OCR chem planning thread? We're doing planning for a titration, so alot of discussion and tips about the methods and maths involved.
However, you people realise its not too late to switch to colorimetry. Its only a plan; you only describe using it, and all the answers are on this thread. I really think all the chemists have been very tempted with this planning to veer off into the chemistry of the question, and this is NOT what the examiners want. They want demonstration of our Biology practical experience, and I think we'll be marked higher if we use that rather than chemistry. I'm doing Chem.. so I know its easy to go into that side of it, but we shouldn't. We don't get marks for sounding smart! Only for answering the question through BIOLOGY. (Sorry.. that was for everyone.. not just you cksjohns!)

Reply 583

cvincecvince

do we really need to go into detail about how aspirin is broken down in the body, exceted and how urine pH affects this. surely it's ok to say u would use the same person in the method

You're going to need to include enough detail to justify everything you do and why.. what theory its all based on, and you're going to need to show you have an idea of exactly how the body processes the aspirin. How else will you get marks for AS and A2 Bio knowlege?

Reply 584

croakly

hi ... so the equation to find how much is left in body = initial intake - left in urine

to get the % left in urine i would just use the calibration graph and get the %.
say it was 1% salicylic acid in the urine. i would then convert to conc.

1% = 10gdm^-3 right... ( 10/1000 = 0.01 * 100 = 1%)

( i dunno if it right... i think those were from previous pages)
How would i estimate the amount left in the body?

would i just say the person had 1.5%... convert to conc then minus the two conc... or that wouldnt work?

Also would gdm^-3 * dm3 = g ( would the dm3 cancel?) and g*1000 = mg

finally i have been reading through the posts and i am totally confused whether we should plan to test on humans( eg a receipe that they can follow)... if not do we state a method which could be applied by humans to find the estimate amount left in the human body and do they want the estimate left in body to be in conc or mass?

Reply 585

croakly

hi ... so the equation to find how much is left in body = initial intake - left in urine

to get the % left in urine i would just use the calibration graph and get the %.
say it was 1% salicylic acid in the urine. i would then convert to conc.

1% = 10gdm^-3 right... ( 10/1000 = 0.01 * 100 = 1%)

( i dunno if it right... i think those were from previous pages)
How would i estimate the amount left in the body?

would i just say the person had 1.5%... convert to conc then minus the two conc... or that wouldnt work?

Also would gdm^-3 * dm3 = g ( would the dm3 cancel?) and g*1000 = mg

finally i have been reading through the posts and i am totally confused whether we should plan to test on humans... if not do we state a method which could be applied by humans to find the estimate amount left in the human body and do they want the estimate left in body to be in conc or mass?

Conc or mass is your choice. There's no right or wrong. Its your experiment.. it just has to be feasible.
The question clearly warns against using humans or real urine. I think that means don't even include it in the plan. Use the plan to create a scale of reference that would be a source against which urine samples could theoretically be compared to get an idea of aspirin conc. Don't waste time feeding the person aspirin and taking samples of urine at intervals. Evidently not what they want us to do. Dilution series in a lab.. and then a calibration curve that one could compare a tested urine sample against.
(in my opinion)

Reply 586

Bang Bang you're dead, always so easily led

Reply 587

tctc

Bang Bang you're dead, always so easily led

??? .....*?* :confused:

Reply 588

Craghyrax

??? .....*?* :confused:

Its a lyric.. but it seems to be fitting, everyone is trying to get everyone to help them so there getting different input from different people mostly conflicting, which makes it even more confusing.
:biggrin:

I did the planning exercise without looking out this thread :biggrin:

i came on after... everyone got a total different way to do it

Reply 589

tctc

Its a lyric.. but it seems to be fitting, everyone is trying to get everyone to help them so there getting different input from different people mostly conflicting, which makes it even more confusing.
:biggrin:

I did the planning exercise without looking out this thread :biggrin:

i came on after... everyone got a total different way to do it

Agreed. As I said, there's no wrong or right.. its our experiments to design. Alot of people do seem to be making it harder for themselves though!
I'd done most of mine before I came on.. and figured most of the stuff out with research. Handed it in two tuesdays ago. Still fluffing about on tcr cause I've got another one for Chem.

Reply 590

Craghyrax

Agreed. As I said, there's no wrong or right.. its our experiments to design. Alot of people do seem to be making it harder for themselves though!
I'd done most of mine before I came on.. and figured most of the stuff out with research. Handed it in two tuesdays ago. Still fluffing about on tcr cause I've got another one for Chem.

We do prac for phys and bio, and cw for chem... chemistry cw our teachers refuse to give us full marks cause there scared of the moderators... Phys was the hardest.

Reply 591

cksjohns

1

Can someone please briefly explain how aspirin goes from blood>kidne>urine to me, or point me to where I may be able to find out?

thx

Reply 592

cksjohns

Can someone please briefly explain how aspirin goes from blood>kidne>urine to me, or point me to where I may be able to find out?

thx

Please dont correct my spelling :P
ok travels in plasma, at kidney it leaves blood in the glomeralus into the Bowmans Capsule (as small)... no selective reabsorbtion. so its pretty much the same for any small molecule

Reply 593

beebee23

cksjohns

Can someone please briefly explain how aspirin goes from blood>kidne>urine to me, or point me to where I may be able to find out?

thx

http://www.bioeng.auckland.ac.nz/physiome/ontologies/urinary/tissues.php

is a good website, scroll to the very bottom where it talks about tubular secretion, i had trouble getting my head around it but this explains it clearly. if the link doesn't work, google "tubular secretion" it should be the 4th one down, a New Zealand website.

hope this helps.

Reply 594

beebee23

cksjohns

Can someone please briefly explain how aspirin goes from blood>kidne>urine to me, or point me to where I may be able to find out?

thx

http://www.merck.com/mrkshared/mmanual/section22/chapter298/298e.jsp

try that too, it starts off with scary language but scroll way down to renal excretion it explains it in not so scary language (well mostly)!

Reply 595

cksjohns

1

Just wondering, I couldnt be bothered to do a preliminary expt. so I made up data for the calibration curve:
Aspirin concentration / % - Optical density / % Transmission
0.0 98.7
0.3 85.4
0.6 67.2
0.9 52.5
1.2 37.1
1.5 19.8

Am I ****ed?

Reply 596

the1andonlyk

anyone know how to work out the serial dilutions from the 1.5% sln.????

Reply 597

tctc

We do prac for phys and bio, and cw for chem... chemistry cw our teachers refuse to give us full marks cause there scared of the moderators... Phys was the hardest.

How tiresome! Chem Planning exercises are SOOO much easier than the Bio.. unbelievable! Bio just gives far more room for them to make it ambiguous and give you something out of the blue that requires you to think out of the box a bit (plus research) to sort out. I mean that generally for Bio..btw.. even thoughy mostly Bio is much easier than Chem. In Chem with the planning..there's only one or two things they can do.. so its really easily to instantly suss and then its just jumping through hoops. I can imagine them having loads of room to turn Physics planning into a nightmare!
I suppose with you doing CW for Chem you're getting a better education than us.. :rolleyes:

Lucky you!

Reply 598

croakly

Hi, im on the edge of finishing this planning but i think i need more points on the following questions:
1) describes ways of obtaining reliable results... eg you could use 10 or more people in the experiment- consistency
2) explain how precise results could be obtained.( is this asking about accuracy like use syringes?)
3) comments on precision and reliability
4)validity of investigation ( what does this mean?)

all these just seem to ask about the same type of thing... what differs precise and realiability? is precise getting it to the right figure as possible and realibility is fair testing or validity is fair testing... hmmmm :?
it would be helpful if you can give a few examples referring to this planning... thanks :P

Reply 599