AQA BIOL5 Biology Unit 5 Exam - 22nd June 2011

I think so, you could probably stretch it a bit and go on about localised circuits and inhibition but that's going a bit far.

Reply 1361

Master.K

18

Original post by Ramin Gorji

I'm getting worried how people are really going deep in to some of the topics. All im doing is revising through my notes and doing some question in the book :/ Am i being to naive. Also im going to do most of my essay revision on the last day just planning most of the questions they can ask and reviewing key topics of each of the previous units.

No, it means you're normal like me. :p:

This is TSR which is like 3% of the people actually taking the exam....

Reply 1362

laura123

Original post by Sparkly-Star

Can anyone please explain kineses?

Kineses is a response to a non-directional stimulus (i.e the organism doesn't move towards or away from the stimulus). Instead, the more unpleasant the stimulus is e.g. a high temperature, the more rapidly the organism will move, and the more rapidly it will change direction. This is supposed to increase the probability that the organism will move back into favorable conditions. If the environment IS favorable, the organism will slow down and change direction less often - in this way, the organism is likely to spend more time in the favorable conditions, and increase its chance of survival.

Hope that helped :smile:

Reply 1363

niharika.jha

Original post by Sparkly-Star

Can anyone please explain kineses?

kinesis is movement which is random when exposed to a stimulus; it is designed to increase the chance of the organism coming into favourable conditions

Reply 1364

tehsponge

11

Original post by Destroyviruses

Im abit unsure about gene therapy.

How is the fragment of DNA transcrbed in the human cell if its succesfully inserted. Does it have promotor regions? Can transciption occur outside of the nucleous?

Doesn't the adenovirus insert the DNA directly into the human DNA?

Reply 1365

NRican

Where have we come across Hydrocarbons in AS?

Reply 1366

SkyHunter

I posted this before...but I think its really helpful so I'm posting it again... a few essay questions with analysis :biggrin:

biologysynopticstudentcreche.pdf714.0KB

Reply 1367

Flux_Pav

Original post by TlanTlan

I think so, you could probably stretch it a bit and go on about localised circuits and inhibition but that's going a bit far.

what a localised circuit?
and how the next region of the membrane depolarised?

Reply 1368

Scrubby

11

I don't know if anyone has come across this before but I found a link to some really, brilliant comprehensive notes here:

http://www.studentcreche.co.uk/showthread.php/548-AQA-Biol1-Biol2-Biol4-and-Biol5-Revision-Notes

They have pretty much everything and anything and some extra info which could be useful for the essay. Just thought I'd post it in case anybody wants to do some extra cramming. They are quite long though.

Reply 1369

Flux_Pav

Original post by SkyHunter

I posted this before...but I think its really helpful so I'm posting it again... a few essay questions with analysis :biggrin:

i hope one of these essays comes up !

Reply 1370

SkyHunter

Original post by Flux_Pav

i hope one of these essays comes up !

that's what i'm hoping too :P fingers crossed!

Reply 1371

student777

8

Any tips for the HSW questions or the data handling question? :smile:

Reply 1372

NRican

Original post by student777

Any tips for the HSW questions or the data handling question? :smile:

Look at some questions from past EMPA/ISA's especially about data.

Reply 1373

Thisisj

Original post by student777

Any tips for the HSW questions or the data handling question? :smile:

hey, do you know which papers from the past spec are most relevant to this spec???

Reply 1374

l4ith

10

Original post by Flux_Pav

what a localised circuit?
and how the next region of the membrane depolarised?

If you are talking about the passage of an action potential along an unmyelinated neurone, when it has occurred in one region there will be a large amount of sodium ions that have diffused in to that region. Hence these ions can diffuse along the axon and act as a stimulus for the next region to depolarise; the ions will move in both directions but since the area behind will be refractory an impulse will not be triggered there. As a result the impulse travels in one direction along the whole length of the axon.

With a myelinated neurone, action potentials only occur at the nodes of Ranvier, where there are gaps in the insulating myelin sheath. When an action potential occurs at these points the large influx of positive ions repels potassium ions down the neurone towards the next node of Ranvier. Again the impulse is only propagated in one direction because the previous node will be refractory.

Hope that helped :biggrin:

Reply 1375

NRican

Can anyone ask me some questions on Chapter 16, just learnt it yesterday and I wanna see if anything actually went in my brain :biggrin:

I will do the same in return on a topic of your choosing if you want.

(edited 12 years ago)

Reply 1376

Cyanohydrin

13

Original post by l4ith

If you are talking about the passage of an action potential along an unmyelinated neurone, when it has occurred in one region there will be a large amount of sodium ions that have diffused in to that region. Hence these ions can diffuse along the axon and act as a stimulus for the next region to depolarise; the ions will move in both directions but since the area behind will be refractory an impulse will not be triggered there. As a result the impulse travels in one direction along the whole length of the axon.

With a myelinated neurone, action potentials only occur at the nodes of Ranvier, where there are gaps in the insulating myelin sheath. When an action potential occurs at these points the large influx of positive ions repels potassium ions down the neurone towards the next node of Ranvier. Again the impulse is only propagated in one direction because the previous node will be refractory.

Hope that helped :biggrin:

do you know what actually happens in the myelin sheaths? something must be happening...the way my teacher taught it is was like magic!

Reply 1377

Destroyviruses

13

Original post by tehsponge

Doesn't the adenovirus insert the DNA directly into the human DNA?

It does? If so then all my questions are answered!

Reply 1378

pip91uk

I know this has been discussed a little before, but I really can't get my head around kineses. I understand that it is non-directional and effected by the intensity of the stimulus, but I keep reading that in unfavourable conditions, the organism will move more quickly and change direction more often. But surely walking fast in a straight line is more likely to result in finding more favourable conditions? If anyone can find it online, question 1 on the June 06 paper illustrates the point I'm trying to make, the body-louse turns more often at 35 degrees to stay there longer.

I know it's a minor point that will probably only come up as a one marker, if at all, but it's really annoying me so a quick clarification would be much appreciated :redface:

Reply 1379

Tericon

8

Original post by Cyanohydrin

do you know what actually happens in the myelin sheaths? something must be happening...the way my teacher taught it is was like magic!

I remember back in Unit 1 where my teacher described the reaction between starch and amylase as magic....

Q1. What type of reaction happens between amylase and starch. A. Magic :rolleyes:

The myelin sheath (made up of Schwann cells) is an insulator, therefore, nerve impulses cannot be conducted along it. The nodes of Ranvier (gaps in sheath, so bare membrane) have sodium ion channels concentrated at them, so the cytoplasm for a neurone can conduct enough energy for the nerve impulse to jump to these nodes, opening the sodium ion channels and depolarising this part of the membrane. This is called saltatory conduction and is much quicker than nerve impulse proprogation in an unmyelinated neurone, (impulse has to travel along along axon, not just from node to node).

You don't need to know anything else about the sheath :smile:

AQA BIOL5 Biology Unit 5 Exam - 22nd June 2011

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