Proteins And Amino Acids Flashcards
What are the main functions of proteins ?
Used for transport and structure. The main basic component of all biological matter.
Draw the structure of an amino acid.
In notes.
What are the components of an amino acid ?
Carboxylic acid group
Amino acid group
Hydrogen
Variable region which determines the amino acid
What are the 3 main categories of amino acid ?
Non-polar side chains
Polar side chains
Electrically charged side chains.
How many different types of amino acid are there in the human body ?
20
Where are proteins made
Ribosomes
What is a dipeptide.
2 amino acids joined by a peptide bond.
Draw a peptide bond.
In notes.
Explain in detail how a dipeptide is formed.
A dipeptide is formed by the bonding of two amino acids during a condensation reaction where water is expelled. A peptide bond is created as the hydrogen from one amino acid group and the hydroxyl group from the carboxylic acid from another amino acid is removed.
However, the removal of the hydroxyl group means the carbon and oxygen double bond will rotate to sit directly above the carbon in the peptide bond. While the hydrogen above the nitrogen in the peptide bond will flip over.
What is primary structure ?
Polypeptides. The OH from the carboxylic group and H from the amino group forms a peptide bond which occurs by a condensation reaction.
What are the two types of secondary structure ?
Alpha helix or beta pleated sheet
How are alpha helix’s created.
Alphas helix are caused by hydrogen bonds between slightly negatively charged oxygen in the peptide bond and the slightly positively charged hydrogen in the other peptide bond of another dipeptide.
What is tertiary structure ?
Could and pleats fold together to form a 3D shape. This shape is stabilised by 3 types of bonds.
Disulphide bonds
Ionic bonds
Hydrophobic or hydrophilic interactions
What are the 3 types of tertiary bond ?
Disulphide
Ionic
Hydrophobic or hydrophilic interactions
What is the test for non-reducing sugars ?
Add Hydrochloric acid to the substance. Then neutralise ( maybe with sodium bicarbonate).
The. Heat with benedicts solution.
Give an example of a non-reducing sugar.
Sucrose.
Why does the non-reducing sugar test work ?
Glycosidic bonds are hydrolysed so the sugar returns to its monosaccharides.
Why does Benedicts test work ?
Sodium hydroxide and copper sulphate in Benedicts solution.
The reducing sugar reduced the copper sulphate to copper oxide which is an insoluble red/ orange substance.
What components are in benedicts solution ?
Sodium hydroxide and copper sulphate in Benedicts solution.
What is the test for proteins ?
Biuret test
Add biuret reagent to crushed substance. Lilac colour indicated protein is present.
How does the biuret test for proteins work ?
Presence of peptide bonds in the proteins causes copper ions to be reduced from +1 ions to +2 ions. This leads to a colour change.
Explain what is meant by the tertiary structure of a protein.
The way in which the whole molecule is folded into a globular shape.
How may heating affect the tertiary structure of a protein.
Causes bonds within the tertiary structure to break so the shape is no longer maintained and proteins may be denatured.
Name one chemical element found in all amino acids but not in monosaccharides.
Nitrogen
What is meant by hydroxylating ?
Addition of an OH hydroxyl group
Explain how the amino acids from which proteins are built differ in structure from each other.
They have different r group side chains.
About how many amino acids long is a secondary structure of a protein ?
About 11
Why do the oxygen and the hydrogen in the peptide bond bond by a hydrogen bond.
The O is slightly negative and the hydrogen is slightly positive therefore they attract.
What is a quaternary structure ?
More than one polypeptide bonds to form a complex structure which can have prosthetic groups
What are prosthetic groups ?
Sections in a qutenary structure which are not proteins.
Give an example of a prosthetic group in a specific protein.
The iron in haemoglobin.
What are the 2 main types of quaternary structure and describe them.
Globular protein - round, 3D shape
Ginormous proteins - longer, folded
Where might you find a globular quaternary structure ?
Enzymes
Haemoglobin
Where may you find a fibrous quaternary structure ?
Soft tissue.
