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AQA A2 BIOL5 22nd June 2012

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Did you get your biol4 paper remarked and did you get the script back? I only need a B in Biology, but I know my EMPAs will drag me down. :frown:

I found task 3 of the EMPA awful :frown:

Reply 821

ashleyp

im seeing comments like 2 marks for each paragraph for the essay, can someone please explain this?! i understand its 16/25 for scientific content..

Reply 822

Granger

im confused, is pre RNA the same as mRNA? Or is it something else?

Reply 823

Bright.Inspiration.

Original post by Granger

im confused, is pre RNA the same as mRNA? Or is it something else?

Pre-mRNA contains introns (non-coding DNA)
but splicing takes place to remove the introns and make mRNA, which is then translated :smile:

Reply 824

Granger

Original post by Bright.Inspiration.

Pre-mRNA contains introns (non-coding DNA)
but splicing takes place to remove the introns and make mRNA, which is then translated :smile:

oh really thanks

Reply 825

JJMick

Original post by EffKayy

I found task 3 of the EMPA awful :frown:

I much prefer ISAs, I managed to get 46/50 in both unit 3 and unit 6 :smile:

Reply 826

BodybuildinPassion

Can someone explain cone cells and rod cells? dont know how much of it to learn, Thanks

Reply 827

ChocolatePearl

Original post by BodybuildinPassion

Can someone explain cone cells and rod cells? dont know how much of it to learn, Thanks

In a nutshell.
Rods and Cones are photo-receptors found in the eyes. Your eyes contain circa. 120million Rods that enable you to see black and white images. Cones enable you to see colours and are found concentrated in the fovea. You only have around 6-7million Cones. You can't see colour at night because unlike Rods, Cones are not as sensitive to light and only 'work' with bright light.

These are some of the marking points you need according to AQA,
Rods and cones

•

no rods at blind spot or fovea;

•

greater distribution of rods at edge

•

rods have high sensitivity / show retinal convergence /summation occurs with rods / converse

•

for cones;

•

rhodopsin .bleached. at low light intensities / iodopsin .bleached at high light intensities;

•

higher frequency of rods;

•

better vision in dim light;

•

lower visual acuity;

Hope it helped! :smile:

Reply 828

JJMick

Original post by BodybuildinPassion

Can someone explain cone cells and rod cells? dont know how much of it to learn, Thanks

Rod cells

•

Exhibit high sensitivity due to the fact that many rod cells are attached to one neurone - spatial summation occurs so small generator potentials combine to reach the threshold value and create an action potential.

•

because many rod cells are attached to one neurone two different spots of light close to each other cannot be distinguished as only one impulse is sent to brain.

•

are spread evenly round more towards the edges of the retina.

Cone cells

•

Have high visual acuity as each cone cell is attached to one neurone so different close light spots have separate impulses

•

Have low sensitivity as no summation occurs

•

Are concentrated at the fovea

Reply 829

JJMick

Original post by ChocolatePearl

•

no rods at blind spot or fovea;

•

greater distribution of rods at edge

•

rods have high sensitivity / show retinal convergence /summation occurs with rods / converse

•

for cones;

•

rhodopsin .bleached. at low light intensities / iodopsin .bleached at high light intensities;

•

higher frequency of rods;

•

better vision in dim light;

•

lower visual acuity;

Hope it helped! :smile:

Beat me to it, but I don't think we need to know the names of the specific pigments do we?

Reply 830

ChocolatePearl

Original post by JJMick

Beat me to it, but I don't think we need to know the names of the specific pigments do we?

Its in the markscheme and my teacher mentioned it quite a few times, so yup sadly we do :tongue:

Reply 831

TheBlueNowhere

Original post by ChocolatePearl

Its in the markscheme and my teacher mentioned it quite a few times, so yup sadly we do :tongue:

Which mark scheme? Pretty sure we don't have to know the names of pigments.

Reply 832

ChocolatePearl

Original post by TheBlueNowhere

Which mark scheme? Pretty sure we don't have to know the names of pigments.

Ahh, whoops! :colondollar:

Old spec

Reply 833

umair.khan

Original post by JJMick

Beat me to it, but I don't think we need to know the names of the specific pigments do we?

It could only help you get marks if you learn the names of the pigments, especially for the essay :biggrin:

Reply 834

handsome7654

Original post by JJMick

Rod cells

•

because many rod cells are attached to one neurone two different spots of light close to each other cannot be distinguished as only one impulse is sent to brain.

•

are spread evenly round more towards the edges of the retina.

Cone cells

•

Have high visual acuity as each cone cell is attached to one neurone so different close light spots have separate impulses

•

Have low sensitivity as no summation occurs

•

Are concentrated at the fovea

Doesn't temporal summation occurs with cones??

Reply 835

handsome7654

Original post by BodybuildinPassion

Few questions for the biology wizards, who gets A's/A*

Can someone tell me the marking points for transcription/translation?

Can someone also clarify the role of RNA polymerase in transcription, does it form hydrogen bonds between the RNA nucleotides bases and the exposed bases or does it join the nucleotides together to form pre mRNA single strand?

And in translation, does ribosome join at one end of the mRNA then do complementary tRNA molecules attach? Help appreciated

What do you mean marking points? Do you mean like the starting points? Or the end post transcriptional and translational modification?

RNA forms phosphodiester bonds between a phosphate group and pentose sugars and joins the nucleotides together.

A ribosome attaches to the mRNA at an initiation codon (typically AUG). It doesn't have to be in the end, it may be somewhere within the sequence.
Then tRNA anticodon attaches to the first mRNA codon by complementary base pairing

Btw I'm not a biology wizard or anything so if anyone can correct any mistakes or fill the gaps in my knowledge I would really appreciate, thankyou!

(edited 11 years ago)

Reply 836

Japanese_delegate

Original post by handsome7654

then you'd go onto say about how tRNA carries a specific amino acid and as the next tRNA attaches to the next anti-codon carrying another amino acid. The two amino acids join by peptidyl transcriptase (enzyme) forming a peptide bond between then. THen first tRNA detaches picks up another amino acid and ribosome moves along the mRNA strand

Reply 837

JessChappers01

Iv not started revising for bio yet !!!!
got an exam on monday but when thats done got only this and law to revise for for 11 days letts hope i can fit it all in!

hows everyone revising for the synoptic essay??
Is everyone revising main topics from AS & A2 or just going to rely on thier previous knowledge haha :smile:

Reply 838

George0123

What would you guys include for the essay: " The causes of variation and it's biological importance"?

Thanks in advance :-)

This was posted from The Student Room's iPhone/iPad App

Reply 839

clairelouise444

Original post by dc2012

Hi some essays that i think are bound to come up are the structure and importance of proteins, and importance of ATP. there pretty broad questions and allow you to talk about aspects from all of the units.

Thanks

Do you think they are likely to repeat topics theyve done before?
and if i was doing a variation essay and wanted to include "extra reading" info for more marks, could i talk about something like the variation between humans and animals in terms of distribution of layers in the eye?