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OCR Biology F212 Revision [3rd June 2013] (Now Closed)

Can any one help me I got 72 in the January exam and 32 in the practicals what do I need for an A overall in tomorrows exam??? Any answer will be much appreciated :biggrin:

Reply 1061

cookiess

3

Original post by kited4

do memory cells gradually leave the blood if there is no secondary infection? so is that why we need booster vaccinations e.g tetanus every 10 years
or is that just because of mutations, so different antigens?

I would say it's a combination of the two

Reply 1062

kited4

Original post by Deziah

I think so.
Memory cells will eventually leave the blood so that's why you need a tetanus jab every ten years.
I reckon you'd talk about mutations if you were talking about why everyone can't be given immunity to the influenza virus - seen as it mutates every year.

ahh thanks :biggrin:

i thought so :wink:

Reply 1063

zakir123

Original post by Danny786

7 mark question - Anyone?

Describe the different ways inw hich LDLs and HDLs affect the formation of atheromas?

ldls carry cholesterol from liver to tissues by
receptor on liver for ldl to attach to
increase blood choleterol levels
fats deposited in artery walls
increase chance of atheroma

hdls carry choesterol from tissues to liver by
receptor on tissues for hdl to attach to
decrease blood cholesterol level
reduces deposition of fats in artery walls
reduces chance of developing atheroma

Reply 1064

senS

Anyone has a good approach to suggest questions?

Reply 1065

kited4

Original post by senS

Anyone has a good approach to suggest questions?

i know it's silly but my teacher told us to take 2 huge deep breaths in and out and then think about what knowledge we need to apply! he said he wants to hear our breathing from the exam hall haha :rolleyes:

Reply 1066

phaseshift

12

Original post by senS

Anyone has a good approach to suggest questions?

Read the question twice. I know it sounds ridiculous, but the majority of candidates sitting the F212 (and F215 incidentally) paper just dive straight into answering the questions when their understanding of what's being asked is wrong or warped.

Make sure you understand the question in full, if it helps to leave it and come back try that!

Reply 1067

TSRxRookie

Just spent last 2 days on the TSR biology 3rd june AQA thread by mistake -_- no wonder i was so confused xD

Reply 1068

Beni24

2

Whats a prosthetic group?

Reply 1069

TSRxRookie

I wondered if anyone could help me with this part of the specification?

Describe how the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity can be investigated experimentally.

Reply 1070

HelenPaddock

The following tests are part of the specification for biological molecules, could someone please bullet point how to do each one as you would get marks for on the mark scheme. Thank you!
(r) describe how to carry out chemical tests to identify the presence of the following molecules: protein (biuret test), reducing and non-reducing sugars (Benedict’s test), starch (iodine solution) and lipids (emulsion test);
(s) describe how the concentration of glucose in a solution may be determined using colorimetry (HSW3).

Reply 1071

phaseshift

12

Original post by TSRxRookie

I wondered if anyone could help me with this part of the specification?

Describe how the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity can be investigated experimentally.

You just need to design an experiment to look at enzyme activity. Take a real example, so the breakdown of lactose, using lactase and just tweak the conditions.

Reply 1072

Ambitions

2

Original post by Beni24

Whats a prosthetic group?

A prosthetic group is a co-enzyme (non-protein, organic substance) that binds permanently to an enzyme.
They are vital to the overall function of the enzyme- for example the Haem group (Fe2+ ion in haemoglobin) has an affinity for oxygen and is involved in transporting oxygen from the lungs to the tissue to respiration to occur.
Also, the Zinc ion is a prosthetic group found in carbonic anhydrase in red blood cells involved in catalysing the combining of CO2 and H2O to produce carbonic acid and is involved in transporting of CO2 in the blood.

Reply 1073

nevarsan

Original post by Beni24

Whats a prosthetic group?

A coenzyme that is a permanent part of an enzyme molecule. Its vital for its function, contribute to the 3D shape.
Hope this helps.

Reply 1074

Beni24

2

During Semi-conservative replication, is 'DNA unzips' the same as saying The hydrogen bonds between the bases are broken apart?

Reply 1075

HeyMickey6

Original post by Ambitions

A prosthetic group is a co-enzyme (non-protein, organic substance) that binds permanently to an enzyme.
They are vital to the overall function of the enzyme- for example the Haem group (Fe2+ ion in haemoglobin) has an affinity for oxygen and is involved in transporting oxygen from the lungs to the tissue to respiration to occur.
Also, the Zinc ion is a prosthetic group found in carbonic anhydrase in red blood cells involved in catalysing the combining of CO2 and H2O to produce carbonic acid and is involved in transporting of CO2 in the blood.

Isn't Fe2+ in-organic tho ?

Reply 1076

phaseshift

12

Original post by Beni24

During Semi-conservative replication, is 'DNA unzips' the same as saying The hydrogen bonds between the bases are broken apart?

Yes, but the second part is far more scientific. I'm not sure that "DNA unzips" is creditworthy in all honesty.

Reply 1077

Beni24

2

Original post by HarryMWilliams

Yes, but the second part is far more scientific. I'm not sure that "DNA unzips" is creditworthy in all honesty.

Yeah Just wanted to make sure! Thank you!!

Reply 1078

username972634

Original post by jollygood

In characteristics of discontinuous variation, what does it mean when mark scheme says its Qualitative and affected by few genes and few environmental factors?

Continuous variation is quantitative as it has a measurable range of intermediates e.g. height/weight. This is determined by both genes and the environment. e.g: you need to have tall parents and eat a balanced diet.
Whereas discontinuous variation is qualitative as it consists of two or more discrete/distinct categories with no intermediates. e.g. gender or eye colour. This is determined by genes only.

Source:textbook

Reply 1079

Hellomrnut

Original post by TSRxRookie

I wondered if anyone could help me with this part of the specification?

Describe how the effects of pH, temperature, enzyme concentration and substrate concentration on enzyme activity can be investigated experimentally.

Explain an experiment using the water displacement method (Water bath, delivery tube, test tube filled with water upside down in the water bath and a conical flask where the experiment is taking place with the cork and delivery tube attached at the top)
An example is the breakdown of H₂O₂using the enzyme catalase to form H₂O and O₂
The release of O₂can be recorded in the volume of gas collected from the delivery tube into the water bath and the rate of O₂ collection is effectively the volume of Oxygen collected divided by the time taken
Record these results, make a graph etc
Change each variable (pH etc) keeping other variables constant
Record the effect of these variables on rate of reaction (enzyme activity)

Hope that helped

OCR Biology F212 Revision [3rd June 2013] (Now Closed)

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