3.1.4.1 Proteins - structure, function and biuret test Flashcards
What decides the amino acid sequence that determines the primary structure of a protein?
A DNA sequence
Describe the ionic bonds that hold the tertiary structure of a protein in place.
Weaker than disulfide bonds
Easily broken by changes in pH
Form between free carboxyl and amino groups in the polypeptide chain
How would you carry out the Biuret test for proteins?
- Place a 2cm3 of food in a test tube.
- Add 2 cm3 of sodium hydroxide solution at room temperature.
- Add a few drops of very dilute copper (II) sulfate solution (Biuret reagent)
- Observe and record colour change.
Which colour does Biuret solution turn in the presence of protein?
Biuret changes from blue to purple.
What does Biuret reagent contain?
Concentrated Copper (II) sulfate solution
Describe the disulfide bonds that hold the tertiary structure of a protein in place.
Strong
Not easily broken
Occur between two cysteine amino acids
What do we call 2 amino acids chemically joined together?
Dipeptide
Name the bonds that hold the tertiary structure of a protein in place.
Disulfide Bonds
Hydrogen Bonds
Ionic Bonds
Name 3 fibrous type proteins
Collagen
Keratin
Silk
What do the below instructions describe:
- Place a 2cm3 of food in a test tube.
- Add 2 cm3 of sodium hydroxide solution at room temperature.
- Add a few drops of very dilute copper (II) sulfate solution (Biuret reagent)
- Observe and record colour change.
The Biuret test for proteins.
Identify the molecule
Amino acid
What is the monomer unit of a protein?
Amino acid
What is meant by a fibrous protein?
A protein made from many parallel polypeptide chains. These chains main form an α helix shape.
Fibrous proteins are usually insoluble in water.
Give 3 examples of enzymes
Amylase
Protease
Lipase
Give 2 examples of hormones
Insulin
Oestrogen
What is the function of the protein keratin?
the main component of hard structures such as hair, nails, claws and hooves.
What is meant by the primary structure of a protein?
The sequence of the amino acids in the polypeptide that forms the protein.
Which colour does Biuret reagent turn in the absence of protein?
It remains a blue colour