A2 Biology OCR June 2015 Revision Thread

Are beta galactosidase and lactose permease, the enzymes synthesised when lactose is present in the environment, considered secondary metabolites? Because they are not synthesised during normal growth but only at specific stages of growth. Is this correct?


Posted from TSR Mobile

Reply to games

I see where you are coming from. However penicillin is only produced by penicillium is certain conditions. Penicillium produces penicillium to kill bacteria, it doesn't require human influence for penicillin to be produced. Penicillin is produced in the stationary phase for example when there is lots f competition for nutrients.

Yeah they are kind of unrelated, but I think they could be linked in an exam question quite easily.

It's similar to how would puberty hormones be classified - primary or secondary? They are only produced at a certain stage of growth, not at all times. Primary metabolites are produced in normal growth. So it's unclear I think how to classify a particular substance/molecule?


Posted from TSR Mobile

I had this issue too when I learned it. Usually they'll give you a growth curve (like in the June 2014 paper) so you'll be able to deduce it from there, or some data or information to help. I wouldn't class turning a gene on or off as different conditions as it happens a lot. But things like competition, presence of oxygen, pH etc are what I'd call a different condition personally. I'd avoid defining it as a product synthesised at a specific stage of growth, as that gets confusing.

I see what you're saying.

However one of the specification points is 'describe the differences between primary and secondary metabolites'
I can imagine this could be asked as a straight up question, so I am unsure what they would want us to say.

Primary metabolites - produced during 'normal' growth, in fact at all stages in the growth of an organism because primary metabolites are the product of essential metabolic processes.

Secondary metabolites - produced not during normal growth, but only when there is competition for nutrients - in the stationary phase of the standard growth curve.

Is there much else possible to say or anything you would say differently?


Posted from TSR Mobile

Hi guys , do we need to know in great detail the structure of Actin and Myosin ? in skeletal muscles

Yes...?

As in e.g. Tropinin having 3 polypeptides . one to bind to actin , on to tropomyosin and calcium ions

A dumb question i know lmao , but just want to be sure im not learning unnecessary stuff

As in e.g. Tropinin having 3 polypeptides . one to bind to actin , on to tropomyosin and calcium ions

A dumb question i know lmao , but just want to be sure im not learning unnecessary stuff

Just know that when Ca2+ is released, it binds onto troponin, which changes its shape.nsince troponin is bound to troponyosin, this moves tropomyosin, exposing the actin binding sites. Therefore you can make cross bridges etc

How's Everyone revising ?


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What is interrupted PCR in simple words
I dnt need the whole process . Just a briefing

I feel like I don't accomplish anything when i try revising inheritance stuff like epistasis

I swear I spent hours on all of that... I don't even want to think about it hahaha I can't get a hang of population genetics.