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AQA BIOL2~3rd June 2013~AS Biology (Now Closed)

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Reply 2820
Avatar for mo_a.95
mo_a.95
Original post by PrimusInterPares
can someone explain how mutation in base sequence changes a protein to make it non functional???
thank you


A change in base sequence leads to a change in the position of hydrogen bonds This causes a change in the tertiary structure and therefore no more enzyme-substrate complexes can be formed :smile:
Original post by Manni
Wow two languages, check you out !!

thank you!

i found it more difficult that how general chem 1 past papers were

yep! Had them exams at the beginning of my exam period so glad that's out of the way


HAHA! I love my languages, can speak 5 in total. :biggrin:

It was much much harder than any of the past papers, hopefully the grade boundaries should be low.

Mechanics or Stats?
Reply 2822
Avatar for Sorro10
Sorro10
5
Original post by PrimusInterPares
can someone explain how mutation in base sequence changes a protein to make it non functional???
thank you


Changes to the sequence of bases in a gene will produce a protein with a different sequence of amino acids, leading to a different tertiary structure.

This altered protein could lead to an inactive enzyme if the active site has a different shape, as enzyme-substrate complex's cannot form.
can anyone help me with this one "Explain how a larger body size is an adaption in a colder climate" 2 marks
Reply 2824
Avatar for sophie15
sophie15
Can anybody go through immunological comparison, just the precipitate parts etc?
January 2013

Question Paper : http://www.mybookezz.com/ebook.php?u=aHR0cDovL2Jpb2ZvcnQuZmlsZXMud29yZHByZXNzLmNvbS8yMDEzLzAzL2FxYS1iaW9sMi1xcC1qYW4xMy5wZGYKQVFBLUJJT0wyLVFQLUphbjEz

Mark Scheme : http://biofort.files.wordpress.com/2013/03/aqa-biol2-w-ms-jan13-1.pdf
(edited 10 years ago)
Original post by BiologyBabe
can anyone help me with this one "Explain how a larger body size is an adaption in a colder climate" 2 marks


Lower surface area to volume ratio
So less heat is lost
Smaller SA:VOL, therefore, less heat is lost
Reply 2828
Avatar for Liam2404
Liam2404
Original post by BiologyBabe
can anyone help me with this one "Explain how a larger body size is an adaption in a colder climate" 2 marks


There is a smaller SA:V ratio, so heat loss occurs at a slower rate :smile:
Original post by BiologyBabe
can anyone help me with this one "Explain how a larger body size is an adaption in a colder climate" 2 marks


smaller sa:volume ratio so less heat lost
Reply 2830
Avatar for mo_a.95
mo_a.95
Original post by BiologyBabe
can anyone help me with this one "Explain how a larger body size is an adaption in a colder climate" 2 marks


A larger body means a smaller surface area:volume ratio, so less heat it lost.
Reply 2831
Avatar for aloha_
aloha_
10
Original post by PrimusInterPares
can someone explain how mutation in base sequence changes a protein to make it non functional???
thank you
Yes, basically when the base sequence is altered the primary structure changes (1 Mark), which alters the hydrogen bonds in the structure (1 Mark), this changes the overall tertiary structure of the enzyme (1 Mark) therefore the active site changes shape and cannot bind with a substrate to form an enzyme-substrate complex (as it is no longer complementary) (1 Mark). Got that off the mark scheme on AQA, hope it helps :smile:
Original post by sophie15
Can anybody go through immunological comparison, just the precipitate parts etc?


Higher precipitate formed = more similar organisms/closely related = because more similar antigens

Posted from TSR Mobile
Original post by sophie15
Can anybody go through immunological comparison, just the precipitate parts etc?



This one i hate!!

Isn't it:

You inject the protein into the organism, which produces specific antibodies. Then you purify these antibodies. You mix these antibodies with the same protein of a different species. Precipitate will form if they species are closely related?
Original post by Sorro10
Rofl

It's on the spec apparently and in the textbook so I don't know what exam YOU are taking
could someone explain q4c on may 2012???
Anyone need help??????
Original post by anonymousecheese
is this right?:
when talking about air entering stomata- its down the diffusion gradient
when talking about water entering the root hair cells- its down the conc grad
when talking about water entering leaf from xylem- its down the water potential gradient


Yep :smile:

Posted from TSR Mobile
Original post by sophie15
Can anybody go through immunological comparison, just the precipitate parts etc?


Choose a protein e.g. Albumin
Inject blood serum from a to b
The extracted b and mix with c
The antibodies formed in b respond by binding to any corresponding antigens in c
This creates a ppt
The more ppt the more complementary antigens b formed so the more closely related the species are
Anyone else feeling the nerves kicking in?

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