biology genetics

[sarahduggan]

im doing a practice paper of AS level foundation and need help with a question. it reads "an enzyme such as amylase, has a specific 3 dimensional shape. explain how dna structure determines the specific shape of enzymes."
its worth 4 marks.
thanks ever so much xx

[bunny29]

I don't think it's DNA structures that does - just the order of nucleotides. That order determines the order of amino acids (based on the triplet code), and the order of amino acids determines things like hydrophobic interactions and bonding between the amino acids (which form hydrogen bonds, ionic bonds, disulfide bridges, etc.) and that's how you get the ultimate 3-D shape of the polypeptide, which is critical to its function.

[Peter Pedant]

hmm quite a good q

the a has changed over 25 years.

the view used to be the the amino acids were churned out and took up the lowest energy configuration [Thermo dynamic view ] When insulin was synthesized, it had 1% activity and everyone shrugged their shoulders

Now there are said to scaffolding proteins (rather after my time I am afraid)

Dna will specify uncharged charged and hydrophlic and lipophilic amino acids, and the charges will tend to segregate, hydrophobic aa turn in and hydrophilic aa turn out

so list the aa which are + charged and state that the DNA here will tend to have the aa separate as far as poss

and then do the same for the - charged

list the hydrophilic and say they're on the outside

and the hydrophobic and say they are on the inside

onemark for ea sentence ?

Protein synth does not occur inn the nucleus so DNA having a scaffoldinng function seems unlikely

Good luck

oh and can you post the answer when it comes ?

[adam163]

im doing A2 bio, and i think you need to talk about dna as a protein, it has a tertiary structure, i.e. 3D structure, but DNA codes for the production of enzymes, i,e, proteins also, so DNA codes for the formation of a certain enzyme such as amylase, cos the code is translated usinf mRNA and tRNA to form the amino acid, (protein)