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

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Reply 620

Ché.

Original post by michmic

Sorry what are the conservation methods?? :confused:

IN SITU?
EX SITU?

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Reply 621

Danny786

On the spec it says:

describe how to carry out chemical tests to
identify the presence of the following
molecules: protein (b
iuret test), reducing
and non-
reducing sugars (Benedict’s test),
starch (iodine solution) and lipids (emulsion
test)

Presence of lipids – emulsion test
Add ethanol to sample then shake thoroughly, then add to water and if it goes cloudy, this indicates that lipid is present.
Presence of starch – Iodine
Add iodine in a potassium iodide solution to the sample, and if there is starch the sample solution will change from yellow/brown to a dark blue/black. Negative results present no colour change.
Presence of protein – Biuret test
Add biuret reagent to a sample. The reagent contains sodium hydroxide and copper sulphate, reacting with the peptide bonds in protein turning the solution to a purple colour if there is protein, and staying blue if there is no protein.
Presence of sugar (reducing or non-reducing)

^ How would you descibe that

I think a 3 marker will come up on this also, but stuck on the method of reducing and non reducing sugars

Reply 622

coco_madem0iselle

Original post by Danny786

Presence of sugar (reducing or non-reducing)

^ How would you descibe that

I think a 3 marker will come up on this also, but stuck on the method of reducing and non reducing sugars

Reducing - Heat + Benedict's solution, if present, brick red precipitate formed.
Non-reducing - Boil with hydrochloric acid to hydrolyse into monosaccharides, neutralise with alkali e.g. sodium hydroxide, carry out Benedict's test, if brick red precipitate formed then non-reducing sugar was present.

Reply 623

Ché.

Original post by AGKhan

Really didn't know how to answer this and the mark scheme didn't help so much, would be grateful if anyone could help!:

Amylase is an enzyme that hydrolyses amylose to maltose (a reducing sugar)

Student investigates action of amylase on amylose. She mixes them and places the mixture into a water bath.

Describe how she could measure the change in concentration of maltose (reducing sugar) as the reaction proceeds.
(8 marks- one for spelling ect)

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I will give it a go...
Literally...
Talk through the practical procedure focusing on the reagents, colour precipitation changes and clear indications on what you would do in an experimental context.

After that?
Focus on the quanta five version of the Benedict's test - this complies with creating a calibration curve and being able create a graphical representation for accurate reading for other intermediates.

That's get you your marks that you need!
- Heating the sample with the Benedict's solution AND Sodium Hydroxide.
- Explain the colour indications for the identification of a reducing sugar.
- Include the correlation from your expected observations - "the more mass of your precipitate, the higher the concentration of the sample in terms of a reducing sugar."
Calorimetry - the curve will represent proportional trends no matter what concentration taken.

MAKE SURE YOU INCLUDE COMMENTS SUCH AS:
- Repeats, replications.
- Proceed three different concentrations for variance.

That's it really...
8 markers aren't exactly too difficult SOMETIMES, haha!

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Thanks

Whats the best ways to answer 6/8 mark questions? :P

ps i have a feeling DNA will be a focus on this one and i haven't come across a question on fertilisers/pesticides yet, maybe preventing food spoilage and something on variation :s-smilie:

i really want a biodivesity question, one that uses the dichotomous key and seed banks please :biggrin:

Reply 626

Unsworth

Just got 85/100 on my final past paper (January 2013) for this exam, praying for a half decent paper after last summers horror one aha.

Reply 627

coco_madem0iselle

Someone help me with seed banks please!
All I know is that they can be reintroduced when the plant species becomes endangered, a lot can be stored and they are less vulnerable to disease. I don't know what else to say about them :/ Disadvantages?
Also if anyone knows some good solid points for pros and cons of Ex-Situ and In-Situ that would be great because I would struggle with things to say.. and just waffle a lot.

Reply 628

xKaylax

DOES ANYONE HAVE THE MARK SCHEME FOR JUNE 2010! Got the paper but the link's broken on the ocr website so can only see half of the mark scheme :/

Reply 629

Danny786

LDL -
Carry cholesterol from liver to tissues, the receptor on the tissue cells raises blood cholesterol, which causes deposit of fat under endothelium which forms plaque

HDL –
Carry cholesterol from tissues, to receptors in liver cells, decreases cholesterol levels, and so reduces deposition of fats so lowers the chance of a formation of plaque.

Is this correct anyone?

Reply 630

own

Original post by Danny786

Yes.

Reply 631

own

Original post by Unsworth

Just got 85/100 on my final past paper (January 2013) for this exam, praying for a half decent paper after last summers horror one aha.

That was unbelievable horrible, so much on tests in the first bit :/

Reply 632

Ché.

Original post by coco_madem0iselle

IN SITU:
Advantages:
- Both the habitat and species are conserved effectively.
- Larger populations can be protected with minimal disruption.
- Species' recover quicker than Ex-situ conservation.

Disadvantages:
- Difficulty of controlling some factors that are actually threatening a species such as Poaching, Predators and Climate Change.

EX SITU:
Advantages:
- it can be used to protect a given species in a controlled environment from Predation and Hunting.
- Competition of sources are reduced.

Disadvantages:
- High expenses; small quantities can be catered for per time.

:biggrin:

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Reply 633

Ché.

Original post by xKaylax

DOES ANYONE HAVE THE MARK SCHEME FOR JUNE 2010! Got the paper but the link's broken on the ocr website so can only see half of the mark scheme :/

I have a copy, actually!
But it's hardback!

Do you want me to photograph some pages?

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Reply 634

kited4

Also In Situ can reduce genetic diversity due to inbreeding therefore increase vulnerability to disease...

Reply 635

morvenrkr

Original post by xKaylax

DOES ANYONE HAVE THE MARK SCHEME FOR JUNE 2010! Got the paper but the link's broken on the ocr website so can only see half of the mark scheme :/

is it attatched?

June 2010.pdf390.1KB

Reply 636

xKaylax

Original post by morvenrkr

is it attatched?

Yes! Thank you soo much! :smile:

Reply 637

lauren1brown

Original post by kited4

Also In Situ can reduce genetic diversity due to inbreeding therefore increase vulnerability to disease...

Does this reduce the gene pool?

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Reply 638

xKaylax

Original post by Ché.

I have a copy, actually!
But it's hardback!

Do you want me to photograph some pages?

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Don't worry someone else has put a link up now but thanks anyway :smile:

Reply 639

Hello...

Original post by Danny786

When the lipid content is high, the level of cholesterol is also high so there is more fat deposited under the endothelium which increases the risk of atherosclerosis due to the blockage of the lumen.

Is this right?

Question: Other than obesity outline why a diet high in lipids might have a negative effect on the health of an individual

I'm not sure that it's directly to do with lipid content... Cholesterol is deposited under the endothelium through the use of LDL's...LDL's are made from saturated fats, protein and cholesterol... The more saturated fats the more LDL's are formed... The more LDL's the more cholesterol transported from the liver to the body tissues and the more cholesterol deposited under the endothelium forming an atheroma which leads to atherosclerosis