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AQA BIOL5 ~ 17th June 2013 ~ A2 Biology

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could someone please give me topics to talk about regarding essay 'receptor molecules and their importance in biology' from Units other than unit 5?

Dna replication from unit 2 - how the dna polymerase binds to primers? antibodies/antigens from unit one? i'm not especially sure if they count as 'receptors' though

Reply 2261

EmilyJane95

Can someone help me to think of ideas what to write if a transfers essay comes up, like I've seen a few like transfers of energy through the ecosystem? Or the importance of DNA and it's transfer through living organisms? Movement of molecules throughout the cell?

Im so nervous about the whole exam and especially the essay! I'm praying its one I know lots on! Nothing to do with bacteria or DNA or nothing to specific fingers crossed!

Reply 2262

YWArtist

Original post by Anjna

to detach them.. atp provides the energy to break the actin myosin cross bridge so the myosin head detaches from the actin filament after its moved ... and then reattaches to a different binding site further alonf actin filament

ATP also provides energy for the initial attachment of the myosin heads to the binding site on the actin filament in the formation of a cross-bridge aswell as for the detachment

Reply 2263

YWArtist

Can someone please explain DNA sequencing as if it was say a 7marker, I know it but just can't word it as I don't understand why it happens

Reply 2264

pinkfairyarmadillo

Original post by starfish232

could someone please give me topics to talk about regarding essay 'receptor molecules and their importance in biology' from Units other than unit 5?

-Enzymes (In digestion (also active transport, co-transport proteins), in DNA replication, ATPase)
-Immunity (T-cells, B-cells and antibodies, immunological comparison of proteins)
-Examples of when shape/fit goes "wrong" (Denaturation, competitive and non-competitive inhibition, cholera toxin?)

Just a few, I wouldn't worry to much about trying to cover all units in the essay, most of the receptor type things are in unit 5, so as long as you have one or two examples from elsewhere it'll be fine :smile:

Reply 2265

CupcakeFaerie

Can someone please go over Restriction Mapping with me? It's the only part I really don't like >.<

Also for the essay, I haven't done Unit 4 for a while and it wasn't my best unit, I'm pretty ok with Unit 1 and 2. Do you think it would be ok just to revise 1, 2 and 5 or should I attempt 4 as well to be on the safe side? Just I know you only need to refer to 3 units xx

Reply 2266

bad8oy

Original post by YWArtist

Can someone please explain DNA sequencing as if it was say a 7marker, I know it but just can't word it as I don't understand why it happens

1. Get many single stranded DNA fragments to be sequenced. These will act as a template.
2. Add radioactively labelled primers to start DNA synthesis
3. DNA polymerase catalysed DNA synthesis.
5. Different lengths of DNA fragment produced as equally likely a normal nucleotide or terminator binds to the template.
6. These fragments can be identified because of primer attached is labeled radioactively or flourescently
7. Gel electrophoresis is used.
8. Shorter fragments travel faster and further on gel due to it being resistive to longer fragments.
9. Fragments radioactive so can be identified through photographic film
10. Read from bottom upwards. Ie: shortest length the longest this will give you sequence of one of strands of newly formed DNA

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Reply 2267

bad8oy

Original post by CupcakeFaerie

Ok basically restriction mapping is needed to piece back the fragments to original genes.

So you cut DNA with different Restriction endonucleases.

You then get fragments of different lengths that are separated using gel electrophoresis.

Distance between recognition sites (where the Reatriction endonucleases cut) is determined by patterns of fragments produced by gel electrophoresis.

You get different lengths depending on which restriction endonucleases are used.

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Reply 2268

sienna5

Original post by CupcakeFaerie

Restriction Mapping

A technique used to find out a base sequence of a gene.
Involves the use of restriction enzymes as most genes will be to long to sequence in one go, so different restriction enzymes are used to allow DNA to split into fragments.The DNA will be labelled.
Gel electrophoresis seperates DNA fragments out, the smaller fragments travel further through the gel so the DNA sepearted out according to size (smaller bottom, heavier the top).
Then a restriction map can be made of the DNA before any cuts with the enzymes were made.

Reply 2269

YWArtist

Original post by bad8oy

Aahh so they bind with 1 of the 4 terminator nucleotide bases (A T C G) the shortest fragment is 1 nucleotide long, second is 2, third is 3, and by this you determine the order?

Reply 2270

LitGeek94

Original post by starfish232

could someone please give me topics to talk about regarding essay 'receptor molecules and their importance in biology' from Units other than unit 5?

- Unit 1- Protein channels/absorption
- Enzymes perhaps eg active site/complimentary shape/lock-and-key model/ induced fit

-Unit 5 - Synapse Impulse Transmission/ Acetylcholine and presynaptic membrane receptors
- Blood Glucose Concentration Control

I suppose it just depends on how you define the receptors in your intro...
Hope that helps :smile:

Reply 2271

CupcakeFaerie

Original post by bad8oy

Original post by sienna5

Ah ok thank you :smile:

I think it's just the working out the lengths part that confuses me, but there's quite a good example in the revision guide so I'll try and memorise that :smile:

Reply 2272

kathrynrc

I'm struggling with the exam technique for this exam for some reason :frown:

I feel like I know most of the actual biology but when it comes to answering the questions I'm lost!

Reply 2273

F1's Finest

Meh, just want this exam over with!

It's worth remembering folkes, that they can ask a restriction mapping question which relates to either a plasmid base sequence or just a single strand of DNA.

Reply 2274

erniiee

I am so screwed, need to get on with essay practice

Reply 2275

Zazuwaved

Original post by YWArtist

ATP also provides energy for the initial attachment of the myosin heads to the binding site on the actin filament in the formation of a cross-bridge aswell as for the detachment

Doesn't it also support the power stroke too?

Reply 2276

gingerandice

Original post by James A

Meh, just want this exam over with!

It's worth remembering folkes, that they can ask a restriction mapping question which relates to either a plasmid base sequence or just a single strand of DNA.

how did you get to understand restriction mapping? I don't get it.... :frown:

Reply 2277

bad8oy

Original post by YWArtist

Aahh so they bind with 1 of the 4 terminator nucleotide bases (A T C G) the shortest fragment is 1 nucleotide long, second is 2, third is 3, and by this you determine the order?

Posted 1 below

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(edited 10 years ago)

Reply 2278

bad8oy

Yeah and all the adenine terminators in one test tube and the cytosine in one and guanine in one and thymine in one. So they are all separate.
And form different lengths so they may be say 2 or 3 different lengths for each fragment ending with a adenine terminator depending on where it binds. It could bind early meaning shorter strand or later meaning longer stand

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Reply 2279

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