BIOL I 100-4
In this practical the lipids present in egg yolk were separated through absorption chromatography using a TLC plate. The concept is similar to paper chromatography, a plate containing a thin hydrophilic layer called a matrix is used, and a non polar solvent is allowed to move up the plate through capillary action. Thus more polar lipids will move more slowly than non polar lipids.
The egg yolk solution was compared against six standards; cholesterol, cholesterol palmitate, trioleine, linoleic acid, phosphatidylcholine, and phosphatidylethanolamine.
The result obtained was that egg yolk contains trioleine, cholesterol palmitate and phosphatidylethonolamine, the latter being the most polar of the three elements hardly moving up the TLC because of the presence of several polar groups; phosphate groups, amine groups and several oxygens , and cholesterol palmitate being the most non polar.
Sunday, March 29, 2009
PRACTICAL 3: IDENTIFICATION OF THE SEQUENCE OF A POLYPEPTIDE
BIOL I 100-3
In this practical the composition of several unknown dipeptides was found using paper chromatography. This is a partition chromatography technique where cellulose in the form of paper acts as a hydrophilic support medium or liquid stationary phase where those aminoacids with polar side chains will interact. A second mobile phase containing water and a non polar solvent was used, the paper was introduced in a chromatography tank where the non polar solvent moved up the paper by capillary action, those amino acids with non polar side chains will move up the paper whereas, as it was said before, those with polar chains will interact with the hydrophilic stationary phase moving up the paper slightly.
The native unknown dipeptide and a hydrolised form of it were compared to six standard aminoacids to find out which were the components of the dipeptide. The hydrolised form will be separated into its constituent peptide residues. The results obtained were:
In the case of dipeptide HA it can be seen that the aminoacid which moves further up is leucine which has a non polar chain:
In this practical the composition of several unknown dipeptides was found using paper chromatography. This is a partition chromatography technique where cellulose in the form of paper acts as a hydrophilic support medium or liquid stationary phase where those aminoacids with polar side chains will interact. A second mobile phase containing water and a non polar solvent was used, the paper was introduced in a chromatography tank where the non polar solvent moved up the paper by capillary action, those amino acids with non polar side chains will move up the paper whereas, as it was said before, those with polar chains will interact with the hydrophilic stationary phase moving up the paper slightly.
The native unknown dipeptide and a hydrolised form of it were compared to six standard aminoacids to find out which were the components of the dipeptide. The hydrolised form will be separated into its constituent peptide residues. The results obtained were:
In the case of dipeptide HA it can be seen that the aminoacid which moves further up is leucine which has a non polar chain:
On the other hand tryphtophane is slightly more hydrophilic because of the presence of an amine group on its side chain:
Overall, amino acids side chains are very important to determine the properties of a protein affecting the way they fold and their structure.
Sunday, March 1, 2009
PRACTICAL 2: Investigating the Chemical Properties of Sugars.
BIOL I 100 – 2
PRACTICAL 2: Investigating the Chemical Properties of Sugars.
The aim of this practical was to test the property of sugars to act as reducing agents. Benedict’s reagent was used to test this property. In this solution Cu2+ ions are reduced to Cu+ by certain sugars changing its colour.
Two monosaccharides sugars, fructose and glucose were used, and to disaccharides lactose and sucrose. Solutions as 0.25% and 1% solutions in water were mixed witn Benedict’s reagent and left in warm water for five minutes. The following table of results was obtained.
As it can be seen the two monosaccharides sugars, fructose and glucose, are clearly reducing agents, this is due to the fact that it is the aldehyde group which gives sugars its reducing properties and in the case of monosaccharides the aldehyde group is free to react as a reducing agent, especially at 1%, this reducing capacity is decreased in a lower concentration. On the other hand the two disaccharides, lactose and fructose, have very little reducing properties in the case of lactose and none in the case of sucrose.This is due to the fact that it is the aldehyde group which gives sugars its reducing properties.In the case of lactose we find two glucose rings joined by glycosidic bond forming an acetal (one carbon joined to two oxygens), the ring with the acetal is non reducing but the other ring still has a hemiacetal (carbon joined to two oxygens one of the oxygens being attached to hydrogen) and is capable of acting as a reducing agent though the reaction is weak.
In the case of sucrose we observe that it is non reducing in both concentrations, this is due to the fact that the glycosidic bond is formed between the reducing ends of both glucose and fructose, therefore both rings are locked and unable to act as reducing agents.
Therefore, Benedict’s reagent could be used as a mean of testing the amount of reducing sugar in a solution as it would result in a different colour depending on the concentration of sugar, and whether it is monosaccharide or disaccharide.
PRACTICAL 2: Investigating the Chemical Properties of Sugars.
The aim of this practical was to test the property of sugars to act as reducing agents. Benedict’s reagent was used to test this property. In this solution Cu2+ ions are reduced to Cu+ by certain sugars changing its colour.
Two monosaccharides sugars, fructose and glucose were used, and to disaccharides lactose and sucrose. Solutions as 0.25% and 1% solutions in water were mixed witn Benedict’s reagent and left in warm water for five minutes. The following table of results was obtained.
As it can be seen the two monosaccharides sugars, fructose and glucose, are clearly reducing agents, this is due to the fact that it is the aldehyde group which gives sugars its reducing properties and in the case of monosaccharides the aldehyde group is free to react as a reducing agent, especially at 1%, this reducing capacity is decreased in a lower concentration. On the other hand the two disaccharides, lactose and fructose, have very little reducing properties in the case of lactose and none in the case of sucrose.This is due to the fact that it is the aldehyde group which gives sugars its reducing properties.In the case of lactose we find two glucose rings joined by glycosidic bond forming an acetal (one carbon joined to two oxygens), the ring with the acetal is non reducing but the other ring still has a hemiacetal (carbon joined to two oxygens one of the oxygens being attached to hydrogen) and is capable of acting as a reducing agent though the reaction is weak.
In the case of sucrose we observe that it is non reducing in both concentrations, this is due to the fact that the glycosidic bond is formed between the reducing ends of both glucose and fructose, therefore both rings are locked and unable to act as reducing agents.
Therefore, Benedict’s reagent could be used as a mean of testing the amount of reducing sugar in a solution as it would result in a different colour depending on the concentration of sugar, and whether it is monosaccharide or disaccharide.
PRACTICAL I: Physical Properties of biomolecules
BIOL I 100-1
PRACTICAL I: Physical Properties of biomolecules.
In this practical the polarity, solubility in water, of different biomolecules was tested. A 1% solution of each compound was prepared and their solubility was tested in ; heptane, acetone, and distilled water. Compounds were classified as soluble, insoluble or partially soluble in each of the solvent solutions. The following table of results was obtained;
PRACTICAL I: Physical Properties of biomolecules.
In this practical the polarity, solubility in water, of different biomolecules was tested. A 1% solution of each compound was prepared and their solubility was tested in ; heptane, acetone, and distilled water. Compounds were classified as soluble, insoluble or partially soluble in each of the solvent solutions. The following table of results was obtained;
It can be observed that cholesterol, which is a lipid, is partially soluble in water. By looking at its molecular structure it could be assumed that it is hydrophobic, however is an amphiphilic compound possessing both hydrophilic and lipophilic properties. This explains the way cholesterol is transported in the blood stream within lipoproteins which are molecules with a water soluble outward face and a lipid soluble inward face. Cholesterol resulted to be insoluble in heptane, this is due again to the amphiphilic nature of the cholesterol molecule, heptane is a long chain of hydrocarbons whereas acetone a carbonyl group with a negatively charged oxygen and a short chain of hydrocarbons, this makes it a more suitable substance to act as a dissolvent for an amphiphilic compound. On the other hand it can be seen in the table of results that cholesterol ester is insoluble in water, but still soluble in acetone. However, it could be supposed by looking at its structure that it is partially soluble in water like cholesterol because of the presence of an extra hydroxyl group, and amide group and a sulfonyl group.
Palmitic acid and taurodeoxycholic acid are also amphiphilic both having a long chain of hydrocarbons and a hydrophilic tail.
Valproic acid, D+Glucose and caffeine are clearly hydrophilic. Leo-Trp dipeptide is soluble in water because proteins have all their polar groups to the outside being thus able to form hydrogen bonds with water.
Finally, the dye mix is clearly hydrophobic being soluble only in the organic compounds.
Overall the more polar groups a molecule has the more soluble it is, and the more non polar the less soluble it is. It is the overall ratio of polar to unpolar groups which is determinant of solubility.
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