Monthly Archives: February 2014
AMINO ACIDS AND PROTEINS!
CALL ME ACID…… AMINO ACID *brings in intro music*
Amino!!!!!!! I think I’ll name my daughter that. Anyways, onto the topic of amino acids and proteins. Amino acids are the initial structures for one of the most important biological compounds out there i.e. PROTEINS. Proteins have many functions in the world we live in today that we know of and don’t know of. To generalise, some of these functions include receptors, channels, transport, enzymes, storage, structural and immune response. Let go a bit deeper into the biochemistry of the building blocks which make up proteins, i.e. amino acids.
ALL THAT R GIRL!!!!!!!!!!
Soooooooooo….. If I show you a Fischer diagram of a molecule, how would you know if it’s an amino acid or not. What’s that? You don’t know? Well I’m not shockedJ. In my own words, an amino acid can be described as an α carbon bonded to four different groups. But not just any four groups. The four groups must be a hydrogen atom, a carboxylic group, an amino group and a R group.
Another question: So how can we distinguish between the different amino acids?
Answer: Via the R groups of course.
What makes each amino acid different is the R group. The R group can range from very small for example Glycine (smallest amino acid) to very large e.g. Tryptophan (largest standard amino acid). The R groups can be split up into different categories.
- Non polar, aliphatic R groups e.g. Glycine.
- Polar, uncharged R groups e.g. Serine.
- Aromatic R groups e.g. Tyrosine
- Positively charged R groups e.g. Lysine
- Negatively charged R groups e.g. Glutmate.
AMINO ACID ABBREVIATIONS
The names of some amino acids can be abbreviated for the purpose of ease. Here is a chart showing some names and abbreviations which can be a three letter code or a one letter code.
MARRIAGE OF CYSTEINE
When two cysteine molecules react with each other, they go through an oxidation reaction where they lose hydrogen. A bond between the sulphurs in the molecules form. This bond is called a disulphide linkage and the new molecule is called cystine. A reduction reaction can take place in cystine where hydrogen is gained and the two cysteine molecules are reformed.
ZWIT ZWIT
Amino acids can exist in the non-ionic form and also the zwitterionic form. It is quite easy to explain how one changes to the other. A proton/hydrogen from the carboxylic group adds itself to the amino group to form the zwitterion. The carboxylic group will now have a negative charge and the amino group will take a positive charge.
DON’T GET IT TWISTED (Ninhydrin reaction vs Biuret’s test)
Did you know that amino acids are colourless? So how do we know they a part of a substance? We test for them….DUH!!!!!!!! But which test do we use? Ninhydrin or biuret? C’mon, are you for real bro? We use Ninhydrin which ONLY test for amino acids and not proteins. Biuret’s test works on proteins ONLY!!!!! In the ninhydrin test, if a purple colour is observed, then the test is positive for AMINO ACIDS. In the biuret’s test the same purple colour means that the test is positive for PROTEINS.
PEPTIDE BONDS!!!!!!!!!!
These are the bonds created between amino acids. When two amino acids react, the carboxylic group of one amino acid reacts with the amino group the other amino acid to form a covalent bond called a peptide bond. The two amino acids joined together are now called a dipeptide. The reaction is a condensation reaction meaning that water is given off.
Carbohydrates- The Bread of Life
Carbohydrates are hydrated carbons with the empirical formula (CH2O)n or Cn(H2O)n-1.
Classification Of Carbohydrates
- Monosaccharides
- Disaccharides
- Oligosaccharides
- Polysaccharides
Functions of Carbohydrates
| Function | Details |
| Acts as a source of energy | Carbohydrates break down quickly to act as quick sources of energy. Note Polysaccharides take longer to be broken down. |
| Storage | In animals- glycogen ( when glucose levels are high insulin converts glucose to glycogon. When glucose levels are low Glucagon coverts glycogen to glucose)In plants- Starch |
| Structure | In animals- Chitin is found in some insects.In plants- Cellulose: major component of plant walls. |
| Pre cursor Molecule | Used as building blocks for other molecules.Example: DNA, RNA |
| Fat oxidation | Carbohydrates are essential for fat oxidation, without carbohydrates it would not take place. |
| Add flavor to the diet | They are also easy to digest. |
Monosaccarides
There are 2 types:
Aldoses- these has an aldehyde group as seen in the molecular description of D-glucose below.
Ketoses- these have a keto group as seen in D- fructose.
How do differentiate a Aldoses from a Ketose?
This is done by looking at the position of the C=O bond on the molecular structure.
Chiral Carbon must have four different groups attached to it. Chiral compounds have same number of carbons however they are arranged differently.
D vs L Sugars & the Chiral Carbon
*this is based on the asymmetrical carbon (chiral Carbon) in glycerydehyde.
* To calculate if it is a D or a L sugar you first must find the Asymmetrical carbon.
*Then look at the OH group
*If the OH group is on the right it is the D form if it is on the left it is the L form.
More than one chiral carbon? No problem… Just follow these easy steps:
*Find the asymmetrical carbon furthest away from the aldehyde or keto group.
*Then determine which side the hydroxl group is on.
No There not twins they are Epimers
Two sugars that differ ONLY around one carbon atom are called epimers.
Hemiacetals OR Hemiketals
Aldotetioses and all monnosaccarides with 5 or more carbon atoms is the backbone occurs predominatly as a ring structure in which the carbonyl group formed a covalent bond with the oxygen of a hydroxl group along the chain.
The formation of these structures are a result of a general reaction between aldehydes or ketones and alcohols to formed hemiacetals or hemiketals.
The Glycosidic Bond
Disaccharides, oligosaccharides and polysaccharides are formed by joining monosaccharides together. The bonds between the sugars are known as glycosidic bonds. These are formed by the enzyme known as glycosyltransferases. Glycosidic bonds are named according to the numbers of carbon connected and the position of the anomeric hydroxyl group.
Table showing Structure and Function of the main Polysaccarides
| Name Of Polysaccharides | Composition | Function |
| Starch-AmyloseAmylopectin | Unbranched chain of alpha glucose with 1,4 glycosidic links and branched chains of alpha glucose units with 1,4 and 1,6 glycosidic links. | Major storage carbohydrate in plants. |
| Cellulose | Straight chains of alpha glucose.Found only in plants | Needed for structural support |
| Chitin | Unbranched chain of beta acetylgucosamine units with 1,4 glycosidic links. | Major part of the exoskeleton of many arthropods. |
| Glycogen | Highly branched short chains of alpha glucose units. |
This week in labs we did the various tests to determine the presence of carbohydrates in a sample. The following flowchart is a basic skeletal representation of the various tests that were done.
Flowchart showing the classification of an unknown carbohydrate
Did You Know!!!!!!!!
- The sole energy source for the brain is glucose
- Lactose intolerance is caused by a lack of lactase
- Honey is considered a food high in carbohydrates. (It is high in natural sugars)
- Principal sites for dietary carbohydrate digestion are the mouth and intestinal lumen.
- Haworth perspective formula commonly used to show stereochemistry of the ring forms of monosaccharide.
- Carbohydrates are more easily digestible than lipids.
- Some dissolvable stitches are made from chitin.
References
Information:
Pamela C. Champ, Richard A. Havery, Denise R. Ferrier, Lippincott’s Illustrated Reviews,(1987-2005), 83
Flowchart:
Pictures:
“D-glucose – Google Search.” D-glucose – Google Search. N.p., n.d. Web. 07 Feb. 2014.
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