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Edexcel A2 Biology Unit 5 (6BIO5) - 22/06/2011- OFFICIAL THREAD !

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Does anyone have any tips for revising the article?
Ive got another exam tomorrow, the day before this exam, so haven't yet focused much on the article (but I've finished all the topic 7/8 theory and done past papers)
For the article I've just read through it a few times, constructed a glossary for words I didn't know and then revised relevant sections from the textbook e.g. gene therapy section and secondary messengers etc. What else can I do?

Also, what the hell is recombinant bacteria? and could someone write a list of the things we need to know for the article? I'm completely lost on it and worrying!

Reply 2101

chemdweeb1234

Original post by Spain'93

Can someone please explain to me the difference between Chemiosmosis and Oxidative Phosphorylation? I seem to have all of the information under Oxidative Phosphorylation :frown:

Also, what are the products for Glycolysis and the Krebs Cycle?

Thank you!!

erm

1) Chemiosmosis is the movement of H+ ions down their electroCHEMICAL gradient through the semi-permeable inter mitochondrial membrane.... Oxidative phosphorylation is just the collective process through which the ADP is phosphorylated to ATP at the electron transport chain... it is oxidative because the redox reactions of the electrons indirectly provide the energy for the phosphorylation of ADP to ATP... and i guess because "oxygen is the terminal electron acceptor"

2) The NET products of Glycolysis are 2 ATP, 2 Pyruvate and 2 reduced NAD

3) The NET products of the KREBS CYCLE PER TURN are 1 ATP, 3 reduced NAD, 1 Reduced FAD, and 2 CO2, and also the oxaloacetate (the 4C compound) must be regenerated to keep the cycle going

Hope that helps

Reply 2102

blush.ox

Can someone plz do me a favour and explain transcription factors, i think i know it, but then i dont :lolwut:

Anyone plz..

Reply 2103

medtobe

Original post by blush.ox

Can someone plz do me a favour and explain transcription factors, i think i know it, but then i dont :lolwut:

Anyone plz..

I too feel the same. :frown:

Reply 2104

ethiokid

Original post by blush.ox

Can someone plz do me a favour and explain transcription factors, i think i know it, but then i dont :lolwut:

Anyone plz..

A transcription factor binds to the promoter region of the gene allowing RNA polymerase to bind. This forms a transcription initiation complex, which initiates the synthesis of an mRNA molecule. mRNA is made and the leaves the nucleus to go and bind to the ribosome in the cytoplasm. Then the normal method of translation occurs.

Hope that helps :smile:

Reply 2105

blush.ox

Original post by darkiee

Are people nervous about this paper, I am

Im soo scared, since unit 4 went **** :colonhash:

after i did alot of work for that :sigh:

I really need to do well in this or im not going uni.

Original post by ethiokid

Thankyou, i understand all that, im more worried about what exactly transcription factors are? Protiens or hormones etc? This is probably a daft question but im really struggling :colondollar:

and also how they can be inhibited :erm:

Reply 2106

hassib

what is pumping iron?

Reply 2107

haydyb123

Original post by hassib

what is pumping iron?

Lifting weights etc.

Reply 2108

bertstare

Original post by hassib

what is pumping iron?

a film by arnold schwarzenegger

Reply 2109

LibbyU

what is recombinant bacteria? and can anyone give any tips for the article? what are the main topics we need to know about?

Reply 2110

ethiokid

Thankyou, i understand all that, im more worried about what exactly transcription factors are? Protiens or hormones etc? This is probably a daft question but im really struggling :colondollar:

and also how they can be inhibited :erm:

Not at all your question isn't daft, I was wondering the same thing myself and I asked my teacher this same question.

Well, transcription factors can either be made of protein (peptide) hormones or of steroid hormones. The difference between the two is that steroid hormones are lipid based where as protein hormones are protein based.

This causes some difference in the way that they interact with the cell membrane. As steroid hormones are lipid based they are able to move through the phospholipid bilayer and into the cell's cytoplasm. Where as, protein hormones are too large and would only be able to enter the cell except by facilitated diffusion using carrier proteins.

So, I guess your wondering how they manage to work.

Well the protein hormone binds to receptors on the cell surface membrane activating a secondary messenger, which then goes of to activate transcription factors or enzymes needed for transcription.

In steroid hormones they are able to physically enter the cell cytoplasm then bind to the hormone receptors. This forms a hormone receptor complex which acts as a transcription factor.

In both cases a mRNA strand is produced at the end of it.

Transcription factors can be inhibited in many different ways. Basically when ever there is a receptor or binding site, the site can always be blocked using a repressor molecule. A repressor molecule has a similar shape to the substrate and just blocks anything else from binding to the receptor/ active site.

So for example with protein hormones the receptors on the cell surface membrane which they need to bind to, to activate transcription factors would be blocked by a repressor molecule inhibiting the activation of the transcription factors. Therefore, there will be no mRNA produced.

Hope that helped
If you have any other questions send them my way.
:smile:

Reply 2111

hassib

)In 1989 , the biotech company Amgen began marketing Epogen,an injectable form of epo produced by recombinant bacteria.Describe the risk of using genetically modified organisms.

does anyone know the asner for this???
How could i relate it do the article?

1 transfer of antibiotic resistance
2 production of harmfull product
3 transfer of viruses from animals to humans

Reply 2112

ethiokid

Original post by LibbyU

what is recombinant bacteria? and can anyone give any tips for the article? what are the main topics we need to know about?

Recombinant bacteria is bacteria which has undergone genetic engineering. New strands of DNA are added to the bacteria's DNA so that when the bacteria experiences protein synthesis a different protein will be produced.

The desired DNA found and cut using restriction enzymes, they are then stuck into the bacteria's DNA using DNA ligase.

Both epo and insulin human growth hormones can be made using recombinant bacteria.

Hope that helps :eek:

Reply 2113

blush.ox

Original post by ethiokid

....

Thankyou sooo much, i think i get it now, i just seem to get confused alot when it comes to biology :getmecoat:

. Pos rep. Thanks again and yeh im sure i'll be back with something else :sigh:

Reply 2114

darkiee

This Unit determines whether i go to UNI or not and am literally ****ting myself. the question style in the past paper are so :s-smilie:

Reply 2115

hassib

Blood and urine of athletes are routinely tested at every competition.Suggest why two samples are taken of each blood and urine????

Reply 2116

LibbyU

Original post by ethiokid

oh, thank you :smile:

I think I kinda knew a bit about it, just didn't realise it was called recombinant! is it where the plasmid is removed from the bacteria and cut using restriction enzymes, then the DNA is spliced onto the plasmid using ligase and the plasmid is put back into the bacteria, and it's left to produce the proteins?

what are the main topic areas we need to know for the article? do we need to know specifically about human growth hormone and do lots of background research on key words from the article? or are they all things that we can get from the textbooks?

Reply 2117

hassib

Why is nobody asnwering me?please comon people i m strugglin

13)*Describe the role of primary and secondary immune response's following IGF-1 gene injection in to the body.

Reply 2118

haydyb123

Original post by hassib

Blood and urine of athletes are routinely tested at every competition.Suggest why two samples are taken of each blood and urine????

Because you're increasing the reliability of your results, by taking only one measurement you're increasing the risk that your result is down to chance. Whereas by taking two of each and corroborating them, you increase the likelihood that your results are a correct representation of substances in the body.

Reply 2119

haydyb123

Original post by hassib

Why is nobody asnwering me?please comon people i m strugglin

13)*Describe the role of primary and secondary immune response's following IGF-1 gene injection in to the body.

Primary response will be that you have the old Macrophages recognizing the pathogens antigens as being 'non-self', undergoes phagocytosis and the macrophage will present the antigen by becoming a APC (forms a major histocompability complex MHC)

T-helper with complementary receptors bind to APC and releases cytokines, and this stimulates clonal selection of the B-lymphocytes.

B-lymphocytes specific to that pathogen will differentiate into plasma cells secreting complementary antibodies, and of course there will be some memory cells.

Now the main thing is that, perhaps in the first infection the "taxicab will release its payload" however, when it comes to secondary infection:

The memory cells are present and can respond quickly to the same pathogen, thus reducing the chance that the second dose of gene therapy will work.