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Practical Examination (AS)

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Practical Examination (AS)

Postby Mahoganyjoint » Wed Apr 10, 2013 1:09 pm

Hi,

i have a practical exam coming up for my AS-Level Biology (UK), i need a few tips on how to tackle it.

Firstly, i'm a distant learner so i have no teacher/tutor and i pretty much learn everything myself and from the guidance of my text book, with that being said, i don't get any time performing practicals and i have a practical exam coming up so i need all the advice i can get.

The first stage of my exam is a PSV (Practical Skill Verification) where the examiner will watch my ability to demonstrate 'safe and skilful practical techniques and make valid and reliable observations', this is the point where i collect raw data. But can anybody help me out with performing Safe and Skilful techniques? What do i need to consider?

This practical exam is very daunting to me because i have no experience. Any help whatsoever will be greatly appreciated.
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Postby marineman » Sun Apr 14, 2013 6:06 pm

You really shouldn't worry about that. All they did for me is watched us to see if we did any stupid things in the lab (so don't set fire to people and you'll be fine, everyone i know got 100% pretty much for turning up). Just wear lab coats, safety glasses and be safe when handling harmful substances (plastic gloves).
If theirs any particular questions you wanna know about it message me.
goodluck and dont worry !
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Postby Mahoganyjoint » Mon Apr 15, 2013 1:37 pm

Thank you for putting my mind at ease :)

Just one question, most of the previous practicals have involved Effects of Substrate Concentration, pH and Temperature on Enzyme activity. Each exam involves 2 tasks which concludes with plotting your data on a graph.

Can there be anything else to look out for, will i use a microscope at any point? i know its hard to predict until the exam has been sat. i just wanted to know what to expect, just incase i went and something popped up that i had no clue about.

Once again cheers for the original reply
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Postby marineman » Tue Apr 16, 2013 12:49 pm

Is your exam board OCR? if so get the OCR biology revision guild (everything you need to know about the as level exams are in there in a reduced format so it makes revising very easy! plus it has a summary of the factors effecting enzymatic activity in 2 pages) if not just read the pages in the book about the factors effecting enzymatic activity, as they may ask a few questions about the test you did and why your graph looks the way it does.
i have high doubts you would need to use a microsope as you would be measuring the rate of enzyme-controlled reactions so probably either measuring how fast a product of a reaction is broken down using the catalase enzyme and measuring how fast oxygen is given off. Or measuring the disappearance of a substrate rather than the appearance of a product (basiccly just using a starch solution with the enzyme amylase and pipetting it into a tray with potasium iodide and idone and timing how long it takes for the starch to vanish).
i cant stress how easy the test is and i think if you want to re-take you get 3 opportunities?
things to remember are how would you make it more reliable (repeat it)
why you need a control
which variables are independent/dependent.

i did do this exam 3 years ago so it may have changed a bit but its sounds very similar!
hope this helps
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Re: Practical Examination (AS)

Postby Mahoganyjoint » Tue Apr 16, 2013 3:07 pm

The examining board is AQA, I've actually just found out what the exam is about.

"You will investigate the effect of surface area to volume ratio on the uptake of a substance.

In addition, you will need to understand the following topics:

· Diffusion

· The effects of emphysema on lung function

· Cigarette smoking and the risk of coronary heart disease

· Size and surface area

· Gas exchange"

Im guessing it'll be about the Phenolphthalein Jelly, i cant see what else it can be.

Thanks for your Help Marineman
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