Hi my name is mark coughlan ,I'm a 3rd year biolody student in ireland,I am currently studying for my exams ,and I'm doing past papers, I'm having touble finding the answers to some questions can you please help me.

1.why do amino acids rotate polarised light?
2.why do amino acids act as powerful buffers?
3.what is the importance of barley starch in brewing,of wheat starch in breadmaking,and corn starch in the production of sugar syrups.
4.whats the difference between the biuret and bradford techniques for quantitative measurement of proteins in solution,what are the advantages and disadvantages of both?
5.how dofree amino and carboxyl groups of amino acids ionise in water? how does the amino acid react with added acid,added base and what id their importance of these and similar reactions of proteins in foods?

I can answer only 2 of your questions
1)amino acids rotate plane polarised light, because, they are chiral molecules(please refer to stereoisomerism, in organic chemistry)
2)amino acids acting as buffers is a property(like their rotation of polarised light), based on their structure.with a carboxylic group as well as an amino group, they have both acidic and basic properties, now depending on the number of these, they can be neutral, acidic or basic and these properties help them to act just like buffers.
5)amino acids uually exist in the zwitterion form in solution. With the hydrogen of carboxylic group shifted to the amino group, producing an NH4+ ION on one side and a COO- on the other, and hence ionised