AQA BIOL5 ~ 17th June 2013 ~ A2 Biology

What joins the new chain with all its phosphodiester bonds to the existing chain then? By that I mean the hydrogen bonds between the bases? This is confusing as in many of the A level books, they say that DNA polymerase does this, but clearly it doesn't!

hey guys hope revision is going well. I have a couple of questions. When writing the essay how much detail do you put into it e.g. if i am writing an essay on cycles and i mention the nitrogen cycle, do i just give a summary of the processes, ammonifcation, nitrification etc.? Also in terms of the content for biol5 i was under the impression that you memorise processes extremely precisely but my teacher said you just have to know like a summary in your head but know the key terms associated with each step of the process. Is this what you guys do?
Thanks

Haha oh yeah i'll edit it now.

EDIT: Fixed i think

So restriction endonucleases must be used in in vivo cloning as then you need to use the same one to cut the plasmid? If you used reverse transcriptase to get the DNA fragment then you'd have no identical restriction endonuclease to use to create complementary sticky ends on the plasmid, as you haven't used one! Right?

Guys im a bit confused. It says in the nt textbook a neuromuscular junction is the point where a motorneurone meets a skeletal muscle fibre right...but on pg 174 of nt text book it says...a synapse is the point where the axon of one neurone connects with the dentrites of another neurone or with an effector..

So therfore am I right in saying...in the neruomuscular junction the MOTORNEURONES AXON connects with the MUSCLE FIBRE (being the effector) and the way this connection happens is via the synaptic cleft right?
Sorry just really confused but please if you can .

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I wish these books would be more specific... Once the resting potential has been established, and is being maintained, are all sodium and potassium gates closed, aside from those that are permanently open? A good reliable source on this would be great

Page 174 is talking about a sensory neurone stimulating another adjacent sensory neurone OR a motor neurone stimulating an adjacent motor neurone.

They say neuromuscular junction for a reason, because a motor neurone can communicate with an adjacent muscle fibre. Yep, happens at a synaptic cleft (this applies to all other adjacent neurones).

Hello,
Thank you for your reply James .
So can I confirm my wording is correct; a neuromuscular junction is the point where the axon of a motor neurones comes into contact with the muscle fibre via synaptic cleft, and the muscle fibre does not have dentrite or does it?

Thanks!

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James why are you such a Biology God...

The motor neurone doesn't physically come into contact with the muscle fibre, but it does meet at the synaptic cleft. Remember the synaptic cleft here is the tiny space between the neurone and the muscle. The muscle fibre has no dendrites, why would it need any?



You're welcome!

James why are you such a Biology God...

Got it! Thanks One more thing I think (see image below)..I don't get; an electrical nerve impulse goes through the sensory neurone (which has dendrites and an axon to carry the nerve impuse to the intermediate neurone which had the dentrites aswell to carry the impulse to cell body of relay neurone which is theb passed to the motor neurone via the axon. RIGHT...here im confused...say you have this relay neurone right and the nerve impusle moves away from cell body via axon..does it then pass the nerve impusle to the motorneurone dentrites??? Via the synaptic cleft?? So thats how it gets to the motor neurone?

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That's right.

Remember you always need the synaptic cleft when one neurone is transmitting neurotransmitters to another.

BOOM! Thanks! But one thing that trips me up is this picture below;
Why has the axon got dentrites on it? Its a motorneurone hence should connect to an effector (muscle fibre via neuromuscular junction) so why has it got dentrites at the end?

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No, you have loads of motor neurones connecting each other, you will eventually reach a point where a motor neurone eventually reaches a muscle fibre.

I know it's a bit early but I'm going to try and revise as I go along so I thought there should be a place ready for any questions anyone might have as we go along and learn the content.

Also a place to discuss ISAs/ EMPAs, in my opinion the worst part!

For now, here's the answers to the exam style questions:

That's right.

Remember you always need the synaptic cleft when one neurone is transmitting neurotransmitters to another.

all the individual sodium gated channels and the potassium gated channels are shut. The only thing that happens is that the sodium potassium pump actively transports sodium ions out of the cell (neurone) and actively transports potassium ions into the neurone.