AQA BIOL5 Biology Unit 5 Exam - 22nd June 2011

Hey!

Right, so I know aerobic resp. requires o2 but where specifically in the krebs cyle is o2 used?

Glycolysis & Link reaction - don't need o2

Krebs?

ETC - as the final acceptor

Thank you!

It's used in the electron transport chain as the final electon acceptor, if there's no oxygen, the electrons can't be released from the chain, so reduced NAD/FAD stops being oxidised because the chains are full, there's no FAD/NAD to reduce during the Kreb's cycle. Glycolysis can still take place because when pyruvate is converted to lactate, it oxidises the reduced NAD/FAD so there's always a supply :redface:

Reply 641

kingsmod1

guys have u got any spare bio 5 Qs where i can get them
or files of past bio 5 Qs please not the most recent 1!

many thanks x

Reply 642

rrelish

Original post by .Hayley.

Can anyone explain 'transforming' specifically the antibiotic resistance markers section.

The book is really confusing me

Thanks :smile:

Transforming a bacteria is basically inserting a new gene into it, usually via a plasmid.
To get the desired gene into the plasmid in the first place, both are cut using the same restriction endonuclease enzymes. This means they will both have complementary "sticky ends" and so can be joined exactly by DNA ligase.
The plasmid then has to be put into the bacteria:
It is warmed and in the presence of Ca2+ ions the permeability of the cell membrane of the bacteria increase so the plasmid is taken up :smile:

BUT:
- Only as few as 1% of bacteria take up the plasmid and
- even if they do take it up, the plasmid may not have incorporated the desired gene in the first place, it may have closed up.

1) Use antibiotic to find out which ones took up the plasmid (with and without the new gene)
Say Plasmid has 2 anti biotic resistance genes a and b, and we put the new gene we want in place of b.
- Grow all the bacteria on a medium of antibiotic A, to find out which bacteria took up the plasmid. The ones that survive have got the plasmid :clap2:

(We dont use antibiotic B becuase the transformed bacteria would die also, and we wouldnt know which one it was)

Antibiotic resistance markers:
- So now you've got the bacteria with the plasmids, how to tell if the plasmids have the new gene or not?
- Grow on a agar plate, to develop into separate colonies
- transfer each colony onto a 2nd (replica plate) in the exact same position as they were on the 1st. This plate has the antibiotic B on it.
- The bacteria that that die on this will have the NEW gene, on the plasmid in them. (because this gene was replaced in the first place, and so bacteria is not resistant against it anymore)

Finally, match the place the bacteria is missing from the 1st plate, and those are your transformed bacteria :smile:

You can they grow them on a large scale.
E.g insulin

There are enzyme and fluorescent marker too

I got carried away there but hope that helps! :biggrin:

(edited 12 years ago)

Reply 643

Jasmine_009

how did everyone do in the past papers?? i am kinda worried i havent even finished my revision!!! argggh!!!

Reply 644

skygirl999

6

Does anyone know what the bond is called which is produced from a condensation reaction?

Reply 645

Zakir

2

Original post by skygirl999

Does anyone know what the bond is called which is produced from a condensation reaction?

i think its a glycosidic bond??

not too sure though..

Reply 646

rrelish

Original post by skygirl999

Does anyone know what the bond is called which is produced from a condensation reaction?

It depends what two monomers you have
In carbohydrates its a glycosidic bond (2 monosaccahrides)

In proteins its a peptide bond (2 amino acids)
http://www.biotopics.co.uk/as/aminocon.html

And In lipids its an ester bond (normally triglyceride so 3 bonds to a glycerol)

:biggrin:

Reply 647

SashaLuLu

Original post by skygirl999

Hi all, I just came across a past paper question which has completely stumped me, and I was wondering if anyone has any ideas as to what the answer might be? (I can't look it up because its from an ancient paper, but it is still relevant)

Anyway, at the beginning of the question it gives some information about arrow poisons and curare ... "The experiment showed that the injection of arrow poison into the blood stream causes death by respiratory failure. It is now known that curare competes with acetylcholine molecules for receptors at neuromuscular junctions. Since Watertons work, many other chemicals have been discovered which also affect the nervous system, two of which are anatoxin and saxotoxin. Anatoxin also affects synpases. Its molecules are very similar to those of acetylcholine but they are not broken down by acetylcholinesterase."

Then the question is: "suggest an explanation for the fact that one of the symptoms of anatoxin poisoning is the excessive production of tears"?

I have sat and tried to work it out, but I can't! All I have deduced is that it will lead to action potentials being constantly fired, and I though that in an attempt to get rid of some of the sodium ions the body might try and get them out with tears? (because sodium is in salt, which is in tears) But this doesn't seem like a likely answer, does anyone have any other ideas?

I think it is that the anatoxin is going to bind to the receptors. This will result an action potential being generated as sodium ions diffuse in. However, you know acetylcholinesterase breaks down acetylcholine which allows the action potential to stop, well the anatoxin cannot be broken down by acetylcholinesterase and so anatoxin is producing tears but it is causing excessive production as it is always producing an action potential which stimulates the production of tears. As the anatoxin cannot be broken down you are still getting action potentials therefore lots of tears.
Also correct me if i am wrong but an action potential doesn't just have to happen at a muscle right? so the action potential can be stimulated somewhere to do with tears??

I don't know if it's right, but that's what i would guess!

Reply 648

angel1992

hey, is control of the heart rate homeostasis, because its trying to maintain a constant ineternal environment right??

Reply 649

angel1992

hey if control of heart rate is homeostasis, why isnt it that section in any of the books?

Reply 650

futuredentist30

i really dont know where to begin with synoptic revision??? any ideas?

Reply 651

Jing_jing

14

Original post by angel1992

hey if control of heart rate is homeostasis, why isnt it that section in any of the books?

It's in the NT book in chapter 9 where controlling heart rate is used for homeostasis of blood pH.

(edited 12 years ago)

Reply 652

sophieyay

Are any of you guys revising anything that's not in the syllabus for the essay? My teacher said that it's the only way you can get top marks in the essay, and whilst I'm not aiming that high, a few extra marks would be nice.
I have no idea where to start though. Because we don't know what the essay is going to be about, are we just supposed to learn about everything in whole entire spectrum of biology on the off-chance it will be relevant? XD

Reply 653

angel1992

Original post by Jing_jing

It's in the NT book in chapter 9 where controlling heart rate is used for homeostasis of blood pH.

i know but it doesnt say that control of heart rate is a homeostatic mechanism/

Reply 654

Jing_jing

14

Original post by angel1992

i know but it doesnt say that control of heart rate is a homeostatic mechanism/

When you exercise the increased respiration rate means that CO2 is produced, and this dissolves in the blood lowering the pH as it forms an acid. The change in blood pH is detected by chemoreceptors in the caratid arteries and aorta and sends an impulse to the medulla oblongata, which in turn sends an impulse down the sympathetic nervous system to the SAN which causes heart rate to increase. This means that more CO2 is removed by the lungs and the blood pH returns to the preset level, so it's homeostasis of blood pH.

Reply 655

Destroyviruses

13

Original post by futuredentist30

i really dont know where to begin with synoptic revision??? any ideas?

i made a mindmap , want it?

Reply 656

Destroyviruses

13

Original post by sophieyay

Are any of you guys revising anything that's not in the syllabus for the essay? My teacher said that it's the only way you can get top marks in the essay, and whilst I'm not aiming that high, a few extra marks would be nice.
I have no idea where to start though. Because we don't know what the essay is going to be about, are we just supposed to learn about everything in whole entire spectrum of biology on the off-chance it will be relevant? XD

just learn extra bits on the stuff on the spec that you like. its best if you choose a really broad topic.

Reply 657

cheekymon999

9

not gonna lie - bricking it about the essay....

Reply 658

angel1992

Original post by Jing_jing

When you exercise the increased respiration rate means that CO2 is produced, and this dissolves in the blood lowering the pH as it forms an acid. The change in blood pH is detected by chemoreceptors in the caratid arteries and aorta and sends an impulse to the medulla oblongata, which in turn sends an impulse down the sympathetic nervous system to the SAN which causes heart rate to increase. This means that more CO2 is removed by the lungs and the blood pH returns to the preset level, so it's homeostasis of blood pH.

thankyou soo much i was hoping someone would say that!!!! control of blood ph !! thankyou ive been confused for a few hours this really helped, so basically homeostasis of the blood ph helps remove co2 so co2 causes blood ph change so co2 is the stimulus , , okkk i get it thanx, so this is the interlinking part of biologyyy :P :P
i keep on confusin myself cus i always see things as seperate processes that dont overlap which is stupid reli cus ibiology is about overlapping concepts particularly in this case xx

Reply 659

Jing_jing

14

Original post by angel1992

thankyou soo much i was hoping someone would say that!!!! control of blood ph !! thankyou ive been confused for a few hours this really helped, so basically homeostasis of the blood ph helps remove co2 so co2 causes blood ph change so co2 is the stimulus , , okkk i get it thanx, so this is the interlinking part of biologyyy :P :P
i keep on confusin myself cus i always see things as seperate processes that dont overlap which is stupid reli cus ibiology is about overlapping concepts particularly in this case xx

Glad I could help! And yes, so many parts of B5 link to each other, I guess that's why they set the essay, so you realise how all the different topics interlink!

AQA BIOL5 Biology Unit 5 Exam - 22nd June 2011

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