A2 Biology Discussion and Help

OCR Biology F215:

Could anyone describe what a chromatin is, and what use it has in Meiosis 1?

I couldn't already see an A2 Biology thread however I noticed there was an AS Biology thread so here it is ..

For those who want to either discuss A2 Biology, or even need help

Past Papers: (Specifications are also available using these links)
AQA : http://www.aqa.org.uk/subjects/science/a-level/biology-2410/past-papers-and-mark-schemes

OCR : http://www.ocr.org.uk/qualifications/as-a-level-gce-biology-h021-h421/

Edexcel : http://www.edexcel.com/quals/gce/gce08/biology/Pages/default.aspx

WJEC : http://www.wjec.co.uk/index.php?subject=12&level=21&list=paper


The following Youtube channel contains very good walkthroughs of fully explained Biological mechanism relevant in A2 Biology:
http://www.youtube.com/user/khanacademy/videos

I also have a PDF copy of a guide to writing the synoptic essay containing examples which have gained full marks, so PM me your email and I will be happy to send it

I also have 'exampro' but only for AQA, which I would also be happy to send to anyone who PM's me their email

I have done A-level AQA Biology already so if you need help with anything, just quote me

hi could you help me with a question on biology: the bone and its mechanical properties im studying medical physics and biology and my assignment due in tomorrow im stuck on what the relationship between the microscopic structure and mechanical properties are of bone and ligaments.

Great idea - as with the AS thread.

I've survived OCR AS and A2 Biology so if anyone has anything OCR specific, quote me!

x

Any help here?

Glucose: not filtered out into the urine because it is reabsorbed (selective reabsorption) by the cells living the proximal convoluted tubule.
Urea: low concentration in blood plasma because it is slightly toxic and is transported in solution, high concentrations in the urine as it is removed from the blood plasma and filtered out by the kidneys during excretion.
Proteins: none found in the urine because the basement membrane of the Bowman's capsule prevent proteins which have a mass greater than 69000 filtering through the glomerulus.

Slight nitpick: the GBM is part of the glomerulus, not part of Bowman's capsule. The capsule has no role in glomerular filtration - all three layers arise from the glomerular capillaries and podocytes.

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But aren't the podocytes actually part of the bowman's capsule?

Why when holding steady both flexor and extensor contracts ? Arent they a pair of antagonistics muscle? One contracts one should relax isnt it???@@

I think so too. During flexion (going up) of a dumbbell, the flexor is contracted, while the extensor is contracted during streching (going down). From this perspective the flexor is contracted only by holding the dumbbell steady. I don't know why the extensor is contracted too . Did you have ask your teacher?

If you contract the flexor but not the extensor then you will flex the joint. If you want to hold the dumbbell steady, then you don't want to flex the joint, but keep it in the same position. If you contract both the flexor and extensor muscles then there will be no movement at the joint. Instead it will 'tighten' both the flexor and extensor tendons and fix the joint in a given position ie holding a dumbbell steady.

In other words: to hold a dumbbell or something like that steady, the joint is strained. Thus flexor and extensor are contracted. But if the arm is just flexed or stretched, one of the both muscles is contracted only. Is that right?

Yes

HELP PLS

Hey guys, my AQA biol4 exam is tomorrow.
I'm all set, except I need help with something.

For the electron transport chain (or oxidative phosphorylation) in respiration, when hydrogen ions move down their electrochemical gradient, do they go through ATP synthase or ATPase?