Amino acids Flashcards
What percentage of the body is made up of proteins?
18%
What elements do all proteins contain?
C, H, O and N
What is a structural use of proteins in the body?
Muscle fibres, hair (keratin) and bones
What is a use of proteins in the immune system?
Antibodies
What is a use of proteins in cells for reactions?
Enzymes
What is a use of proteins in the nucleus?
Histone proteins which DNA is wound around
What is a use of proteins in the blood?
Proteins such as albumin or some hormones such as insulin
What is a use of proteins in membranes?
Channel proteins, receptor proteins and carrier proteins
What is the polymer of proteins?
Polypeptides
What is the monomer of proteins?
Amino acids
How is a protein formed?
Amino acids are joined together at the ribosomes which make up the polypeptide which is then folded up into a protein
How many different amino acids are there?
20
How many proteins are essential?
9
How many proteins are non-essential?
5
How many proteins are conditionally essential (needed by growing children)?
6
What is different between amino acids?
Their R group which each has different properties
What parts of the amino acid don’t change?
The amino group and the carboxylic acid group
What are the different types of R group?
They can be hydrophobic, hydrophilic, acidic, basic or charged
Where are non-polar amino acids found?
Towards the inside of the protein molecule
Where are polar amino acids found?
The outside of protein molecules
What types of amino acids will dissolve in water?
Polar and charged (acidic and basic)
What bond forms when amino acids are chemically joined together?
A peptide bond
How are peptide bonds formed?
A covalent bond between the nitrogen of the amino group bonds to the carbon of a carboxylic acid on another. Also, one molecule of water is lost as the hydroxyl from the carboxylic acid reacts with a hydrogen in the amine group.
What enzyme causes peptide bonds to be formed and where is it found?
Peptidyl transferase and it lies in the ribosome
What are the steps for the biuret test?
- 3cm of sample is mixed with equal volume of 10% NaOH solution.
- 1% copper sulfate solution is added a few drops at a time until the solution turns blue.
- The solution is mixed and left to stand for 5 minutes
- If proteins are present, the solution turns from blue to lilac
What are risks of NaOH?
It is corrosive and extremely hazardous to eyes so safety glasses are worn
What are the risks of CuSO4?
It is harmful is swallowed and is dangerous for the environment so it use be disposed of safely.
How does the biuret test indicate the presence of peptide bonds?
Copper (II) ions are reduced to Copper (I) ions which then form a complex with the nitrogen component in the peptide bon in alkaline conditions (due to NaOH). Then, the blue of the copper sulfate turns to violet when the complex forms and indicates if proteins are present.
What is the stationary phase in the TLC method?
Thin silica gel layer applied to thin glass of metal sheet.
What is the mobile phase in the TLC method?
Organic solvent
What does TLC measure?
How different amino acids travel at different speeds according to their ability to make hydrogen bonds with the silica gel (stationary phase) and therefore their solubility in the solvent (the mobile phase)
How do you carry out TLC?
- Wearing gloves, draw a pencil line on the chromatography plate 2cm from the bottom and mark 4 equally spaced dots
- The amino acid mixture in the locution is spotted onto the first dot using a capillary tube, allowed to dry, then spotted again.
- Using a capillary tube, 2 different known amino acid are spotted onto the remaining 2 dots (to be used for comparison)
- The plate is placed in a jar with no more than 1cm of solvent at the bottom and the jar is closed.
- The plate is removed from the solvent once it has reached 2cm from the top and a pencil line is drawn to mark the old solvent front.
- The plate is then sprayed in the fume cupboard with ninhydrin spray.
- The amino acids react with the ninhydrin to form a purple/brown colour and the centre of the spot is marked with a pencil
How a you calculate the Rf value of the unknown amino acid?
The same amino acid will always travel the same distance relative to the solvent under identical conditions so values for each amino acid can be calculated to identify them against known values.
How do you calculate Rf?
Distance travelled by amino acid / distance travelled by solvent front
Why are gloves worn?
To prevent bacteria transfer or contamination
