Edexcel A2 Biology exams (6BIO4) 25th January 2012 exam discussion

lipid droplets ......they come and go ........how can they be STRUCTURES ....!!

the questions on it are so messed up,

giving 2 units in one go must be a pain

okay so in the result plus of the first ever unit 4...and at the end a standardized mark conversion scheme is given....so this means that there isnt any threshold?.....because i checked the grade boundaries for june 2011 and all the marks are the same ........ i think we have to get 96/120 to get an A in this unit...that is 59/90

Have this constant worry about not able to reach the boundary

If you are referring to the B cells, then they produce and inject the anti bodies themselves

Okay, then how about the 70s ribosomes?

yeah they r structures but probably not involved in photosynthesis ! so basically its only grana (thylakoid) structure thats involved in photosynthesis !

can someone explain me gram staining?

It's just another technique used for identifying the type of bacteria (besides the physical appearance, its toxicity + whether its aerobic or anaerobic.

The bacteria are stained - with two results;

Gram-positive bacteria - thick layer of peptidoglycan, which means a more teichoic acid - the acid binds to the crystal violet in the stain and the bacteria will appear blue/purple under a light microscope.

Gram-negative bacteria - thin layer of peptiglycan, which means no teichoic acid. The crystal violet in the stain is readily decolourised and replaced with red safarine, so the cells appears red under a light microscope.

^ Not sure what type of question they'll ask about gram-staining, it'll probably be a graph + explain trend question, or just to list different ways of classifying bacteria - hope this helps though.

oh yes it did...thanks alot.... ..u made it alot easier for me

aimen !!!!! did u do past paperss !!! there was a question regarding rigor mrotis whose answer was drugs in body !!! i mean waaaa....??!!?!?

Any tips for this exam? :/

can someone explain me gram staining?

I'd say learn the mark schemes - knowing the material is only 40% of this exam - the rest if all recalling AS material / reading and interpreting graphs and basically answering exactly how the mark schemes wants you to.

Please tell me that isn't in unit 4?

Please tell me that isn't in unit 4?

Are you doing SNAB (orange book) or green book?

I think what all these guys are saying is in the green book, because there is a context and concept led approach for the same exam. That means some of the stuff they are learning may be extra. Not sure though.