Reflection 3- The Powerful Proteins!!!

Hello everybody!!! This is your boy Trav here! Just stopping by to reflect on the past week of what went down. Well this week was all about proteins, proteins, proteins… oh and can’t forget those amino acids… the building blocks that make up these proteins! So I was so glad to hear that I was given the privilege to reflect on this wonderful topic of proteins. In fact I am very intrigued by proteins at the moment, especially since I recently joined the gym and stuff… and well you know a lot of protein is required in my diet! So the word protein may have special meaning to some; for me it is for Biochemistry and for my muscle building!

So I have been rambling on about this word protein, but what is a protein you may ask? Well a protein is a folded substance that is made up of many amino acids that are linked together by peptide bonds. A peptide bond is simply a condensation reaction where there is a loss of that chemically equivalent to a water molecule and a linkage is formed.

A Peptide bond!

Proteins comes in different levels. These levels include: primary, secondary, tertiary and quaternary structures. Not all proteins make it to the tertiary and quaternary structures though. The primary structure of proteins are basically the sequence that the amino acids are bonded. The secondary structure involves the arrangement of the polypeptide chain to form the alpha helix or beta pleated sheets via Hydrogen bonds ONLY. The tertiary level occurs when these polypeptide chains bond to one another and start to fold. Tertiary structures are held together by four types of bonds. These include: hydrogen bonds, ionic bonds, disulphide bridges and hydrophobic interactions. A great example of these are globular proteins and most enzymes are globular! And finally quaternary, this occurs when tertiary proteins are combined. A great example is haemoglobin in blood which has four globular proteins that surrounds an iron ion (lol) within a haem group.

A haemoglobin molecule and the haem groups!

Now, I am sure you are wondering what amino acids are and what they are made off. Well amino acids are the building blocks of proteins as stated previously and they are made up of an amino group, carboxylate anion, a hydrogen and an R-group, all bonded to a central alpha carbon. To make things easier to comprehend I have put a diagram showing this below.

Can you guess which is the alpha carbon?

Now you may be thinking how do amino acids differ from one another? Well basically the R-groups on each amino acid are different, for example for glycine; it only has a Hydrogen atom as its R-group and it is the smallest while the second is Alanine, with its CH₃ R-group. There are 20 different amino acids, so essentially 20 different R-groups.

I remember in one of my lectures, our lecturer was pronouncing cysteine sort of funny. He told us that we would understand the reason why in a few minutes and surely I understood why when he started to explain the bonding of two cysteine to form cystine. I think u can see why now too lol!

The bond between the 2 cysteine to form cystine is a disulphide bridge or disulphide linkage and it is an oxidation reaction that takes place. An oxidation reaction is when there is a loss of electrons or in this case the loss of 2 hydrogens, one from each cysteine. It is a reversible reaction so that means that a reduction reaction can take place to reform 2 cysteine from cystine. A reduction reaction is basically gaining electrons/ hydrogen for this case… so the opposite of an oxidation reaction.( please don’t be mind-boggled, refer to the picture below lol)

Then he went on to talk about the amino acids that are essential to us. I made a list of them below:

Arginine– our lecturer sparked my interest when he talked about the uses and importance of this amino acid and so I did some research that I would like to share with you a little later.
Isoleucine
Leucine
Histidine
Methionine
Threonine
Tryptophan
Valine
Lysine
Phenylalanine

Just to recap, there are 20 amino acids but these are the 10 essential amino acids that we have to get from our diet as adults (we cannot make them on our own!!!). Oh and to clarify, ALL 20 amino acids are important but the 10 above can only be gained from the diet and nutrition you eat while the non-essential can be synthesized by your body. My lecturer then talked about how it is possible to create non- essential amino acids in the lab that we will see next year! Can’t wait for that! So excited!

I have then learnt that there are two types of proteins, complete and incomplete. Complete proteins are those that contains all the essential amino acids. A good source of complete proteins are from animals (meat). Incomplete proteins are those that do not have all the essential amino acids and a common example are vegetables while an exception to this is beans which are considered a complete protein (Lucky for you vegetarians!).

Beans!!!

So I am sure you are wondering how you test for the presence of proteins or amino acids in a food sample or substance? Sorry, it can’t be done in the kitchen! Must be done in the lab lol. Well I learnt that the Ninhydrin test is used to test for the presence of amino acids (usually colourless before). For a positive confirmation of amino acids present, a purple colour would be seen. There is one amino acid that gives a yellow colour instead of purple and it is Proline. Proline is special in that it forms a ring structure due to the R-group bonding with the amino group and so the N is not free to react with the Ninhydrin. This means that no ammonia is formed and therefore the purple colour is not created. Oh and I would like you to note that this is a test for AMINO ACIDS not for proteins! My lecturer really stressed on that point and he explained it was because you cannot use Ninhydrin to find the presence of proteins. Some interesting facts I found on Ninhydrin… There is a Ninhydrin spray that is used on crime scenes to see and visualize fingerprints that contains trace amounts of amino acids.

Diagram of Proline showing the bonding of the R-group to the amino group to form a ring structure

Are you curious to know what the test for proteins are? Well, the Biuret test is common for testing the presence of proteins in a sample. For a positive Biuret test, the colour changes from a light blue due to the Cu²⁺ions in solution to a purple colour. What happens is the Biuret reagent reacts with the polypeptide chain of the proteins which forms a complex that has a strong purple colour.

Before I leave your presence, remember that I said that I have some information to share with you about Arginine? Well Arginine seems to have some very interesting uses when it comes to body building and muscle growth! Arginine is considered a precursor to nitric oxide which is a vasodilator since it helps to relax and widen blood vessels. This helps with improving the circulation of blood flow to the muscles during workouts. This means that you would get a better supply of the much needed energy! It helps with muscle growth as it is needed for the production of most proteins. L-arginine promotes the release of hormones and fat metabolism. This results in well-toned muscle mass since it reduces the fat stores under the skin and therefore promotes muscle growth. Interestingly enough, Arginine also helps boost the immune system (way to put the icing on the cake). This is excellent as continuous physical activity can lead to overtraining which can cause minor illnesses. Well that’s it for Arginine and from me. Hope you find this interesting as I sure did! Lol. Look forward to part two on proteins from my good friend Rakeeru! Laterz and until next time! Trav out!

References:

Picture References:

Proline diagram-
http:// koofers-static.s3.amazonaws.com/flashcard_images/4ebfb0836c18115133cbbef6d2a7af43.jpg
Beans picture- http://atasteofbrazil.files.wordpress.com/2013/07/beans.jpg
Haemoglobin molecule- http://swift.cmbi.ru.nl/gv/students/mtom/quaternary_haemoglobin.gif
Peptide bond diagram- http://www.mun.ca/biology/scarr/iGen3_06-03_Figure-Lsmc.jpg
Body building logo- http://logos.co/1024/royalty-free-vector-logo-of-a-bodybuilder-over-a-red-circle-by-patrimonio-523.jpg
2 Cysteine forming Cystine- http://mandysbiochemistrylair.files.wordpress.com/2013/04/350px-cysteine_vs_cystine10.jpg
Amino Acid Structure- http://api.ning.com/files/xO6ybWgUbfFlk7GUXm9d8dfR–U-fUdPOJEtDzVGgDY_/aminoacidstruc.jpg