Proteins, fats and carbs
- Created by: _tomhobbs_
- Created on: 26-06-17 09:23
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- Proteins, fats and carbohydrates
- Proteins
- Proteins consist of one or more polypeptides arranged as complex macromolecules. They have specific biological functions. All proteins contain the elements; carbon, hydrogen, oxygen and, nitrogen.
- Amino acids - the monomers - all have the same basic structure; an amine group, a carboxyl group and, an R group. Different R groups result in different amino acids, which there are twenty commonly found in cells.
- Amino acids bond when the amine group and the carboxylic group react.
- The hydroxyl in the carboxylic group of one amino acid reacts with a hydrogen of the amine group of another amino acid. A peptide bond is formed between the amino acids and water is produced. This is a condensation reaction.
- Amino acids bond when the amine group and the carboxylic group react.
- Biuret solution is used to identify the presence of protein. Biuret reagent is a blue solution that, when it reacts with protein, will change color to pink-purple.
- Fats (lipids)
- Fats are large, complex molecules known as macromolecules. They are not built from monomers. Fats contain the elements; carbon, hydrogen and, oxygen.
- Glycerol is an alcohol. Fatty acids are carboxylic acids - consisting of a carboxylic group with a hydrocarbon chain attached.
- Sudan III is used to identify the presence of lipids in liquids. It will stain fat cells red.
- Triglycerides are made by combining one glycerol molecule with with 3 fatty acids.
- Both molecules contain hydroxyl groups which interact, forming 3 water molecules and bonds between the fatty acid and glycerol. These are ester bonds and the process is called esterification - a condensation reaction.
- Phospholipids are modified triglycerides and contain a phosphate group, replacing one of the fatty acid groups.
- Fats are large, complex molecules known as macromolecules. They are not built from monomers. Fats contain the elements; carbon, hydrogen and, oxygen.
- Carbohydrates
- A single carbohydrate (saccharide or sugar) is a monosaccharide. When 2 of these monosaccharides link together, they are called a disaccharide. Polysaccharides are long chains of monosaccharides bonded together.
- The monomers of carbohydrates are glucose molecules. Glucose is a hexose monosaccharide.
- There is alpha and beta glucose, in which the hydroxyl (OH) group on carbon 1 is in opposite positions.
- When 2 alpha glucose molecules are side by side, the hydroxyl groups react. From this, a water molecule is formed and a bond forms between carbons 1 and 4 on the glucose molecules. They are now joined.
- A covalent bond called a glycosidic bond is formed. The reaction is a condensation reaction and the bond formed is known as a 1,4 glycosidic bond. This has formed a disaccharide.
- There are 3 chemical tests which can be done to test for the presence of a carbohydrate.
- Reducing sugars react with the copper in Benedict's reagent. When a reducing sugar is mixed with Benedict's reagent and warmed, a brick-red precipitate is formed.
- Non-reducing sugars must first be boiled with dilute hydrochloric acid to give a positive result when warmed with Benedict's solution. The colour change will be the same as in the reducing sugars test.
- The iodine test is done to test for starch. Iodine dissolved in potassium iodide solution is mixed with a sample. If the solution changes from yellow/brown to purple/black, then starch is present in the sample.
- Proteins
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