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AQA BIOL5 ~ 17th June 2013 ~ A2 Biology

Reply 2400

ChloeEmm

Thank you so much for the help!!
Good luck everyone :smile:

Hope you all do well!

Reply 2401

Anjna

9

explain correlation between temp and speed of action potential ?

Reply 2402

Castiel'

Original post by peebs123

In restriction mapping does partial digest produce more fragments? if so i'm confused as to why, can anyone help?

Restriction mapping is basically the process of genetic fingerprinting so: 1. Use restriction endonuclease enzyme to cut the DNA , 2. Place the several DNA fragments onto agar gel and apply a current to it : Gel Electrophoresis. The longer and larger the DNA fragment the shorter the distance it will travel. Then, place these DNA fragments onto a nylon sheet. Add a radioactively labelled DNA probe to these DNA fragments. Then, place these fragments which is on the nylon sheet onto a X-Ray film. Allow for the X-Ray film to develop and the radioactivity from the DNA probes will identify the position of the DNA fragments. Apologies for the lack of spacing, my space bar doesn't work on tsr

Reply 2403

Castiel'

Original post by Anjna

explain correlation between temp and speed of action potential ?

The higher the temperature, the greater the speed of the action potential up to a certain point because the greater the temperature the faster the rate of diffusion of Na+ ions since these ions will have more kinetic energy. This is only true up to a certain point since if the temperature becomes to high (e.g. above 45 degree celcius) then the Na+ protein channels denature and Na+ ions can't diffuse into the axon membrane and therefore the action potential speed slows down again above this temperature.

Reply 2404

JSN

Original post by Anjna

explain correlation between temp and speed of action potential ?

at higher temp particles have more kinetic E therefore diffusion occurs faster.
additionally respiratory enzymes work faster therefore more ATP so active transport of ions faster.

this is up to a certain point ofcourse as the proteins (channel ions, respiratory enzymes) become denatured.

^ beat me to it..

Reply 2405

peebs123

Do you think an essay on systems e.g respiratory, circulatory, immune etc.. could come up?

Reply 2406

simstaaar

Can anyone hell me on the second messenger model of adreneline and glucagon action - it's on the spec but I have no notes on it!

Reply 2407

natalieslr

Right just done a read over whenever water is mentioned in as or a2 book, was trying to link it with the question 'the role of water in a living organism' please can anybody tell me if the points are valid/irrelevant r they have anything extra.. I am aware some of them are irrelevant but like I said I just picked out wherever it said water ahah.. This is for the essay btw--

-osmosis- definition, osmotic lysis (antibiotics), cholera
-plants- cohesion and tension, root pressure, water loss and stomata response, photosynthesis reaction (turning h20 and O2 into glucose)
-water loss in plants
-water providing dissolved O2 for aquatic plants and fish (possible link to eutrophication)(also possible link to counter current flow?)
-h2o is oxidised to O2 in the LDR
-transpiration
-oxidative phosphorylation (protons, electrons and O2 from blood combine to make water)
-diabetes (if blood glucose is too high, water p is reduced to a point where molecules diffuse out which cause them to shrivel and die)

Really stuck with anything else, I don't think there is that much to talk about, well not enough for an essay in my opinion

Reply 2408

Anjna

9

Original post by Castiel'

The higher the temperature, the greater the speed of the action potential up to a certain point because the greater the temperature the faster the rate of diffusion of Na+ ions since these ions will have more kinetic energy. This is only true up to a certain point since if the temperature becomes to high (e.g. above 45 degree celcius) then the Na+ protein channels denature and Na+ ions can't diffuse into the axon membrane and therefore the action potential speed slows down again above this temperature.

Original post by JSN

at higher temp particles have more kinetic E therefore diffusion occurs faster.
additionally respiratory enzymes work faster therefore more ATP so active transport of ions faster.

this is up to a certain point ofcourse as the proteins (channel ions, respiratory enzymes) become denatured.

^ beat me to it..

thanks!

Reply 2409

Anjna

9

" Outline the sequence of events at the dopamine synapse" ?? help

(edited 10 years ago)

Reply 2410

JSN

Original post by simstaaar

Can anyone hell me on the second messenger model of adreneline and glucagon action - it's on the spec but I have no notes on it!

adrenaline binds to its receptor site forming a complex. the activated complex activates an enzyme which converts ATP to cyclic AMP which then activates another enzyme to convert glycogen to glucose.

Cyclic AMP is the second messenger

(edited 10 years ago)

Reply 2411

Ghost95

Original post by sarahhunt9

what are people getting on practice papers without the essay? cos i got 45/75 and just if thats really bad or not

Well there are only 3 papers available (not including the specimen paper) which is really annoying :mad:

Did June 12 this morning but not the essay and got 63/75 so 84% (raw) which is well into an A which was only 70/100 (with the essay), so not feeling too bad. Just not looking forward to the essay...

Reply 2412

mogg

Original post by peebs123

please could someone explain restriction mapping.. i'm confused, what's partial digest?

right so when you are doing restriction mapping you want the strand to be completely digested by the restriction endonuclease enzyme. This mean that all the possible restriction sites have been used and there are the maximum number of fragments are produced. If it only has been partially digested, it means you will get some random larger fragments where a restriction site has not been recognised and broken apart. does that help?

Reply 2413

HELPIMSTUCK

Original post by JSN

..............activates another enzyme to convert Glucagon to glucose.......

converts glycogen to glucose?

Reply 2414

MLogan

Original post by peebs123

Is ATP used for the formation of cross bridges too or just detachment? :smile:

Formation, the detachment is caused by a new ATP molecule binding to the myosin head :smile:

..I think!

Reply 2415

ans16

Hi everyone,

Sorry, haven't been following the thread closely so this may have already been asked/answered.
Does anyone have any good ideas on what the essay could be on looking at previous papers etc

Thanks

Reply 2416

Castiel'

Original post by Anjna

" Outline the sequence of events at the dopamine synapse" ?? help

Is that a question relating to a specific figure or something? It goes something like this: Action potential arrives at the presynaptic knob which causes Ca2+ channels on the presynaptic membrane to open and Ca2+ ions consequentially diffuse in down a conc. grad. This causes synaptic vesicles filled with acetylcholine to fuse with the presynaptic membrane. Acetylcholine then diffuses across the synaptic cleft and binds to acetylcholine receptors on the post synaptic membrane. This opens Na+ channels on the same membrane and Na+ ions diffuse into the post synaptic membrane down a conc. grad, depolarising it and creating an action potential. This action potential is then propagated onwards.