Proteins Flashcards
What is a dipeptide and a polypeptide?
A dipeptide is a made when two amino acids join together.
A polypeptide is made when more than two amino acids join together.
How do you form polypeptides?
During a condensation reaction a peptide bond is formed between the carbon in the carboxyl group and the nitrogen in the amino group and a water molecule is released.
How do you break polypeptides down into amino acids?
During a hydrolysis reaction the peptide bond is hydrolysed and a water molecule is used to produce single amino acids.
How many different amino acids are there and what makes them different?
There are 20 different amino acids and each contain an R group, which is the variable structure in each different amino acid.
Describe the structure of an amino acid.
Each monomer of a protein consists of a central carbon atom attached to a hydrogen atom, a variable R group, an amino group and a carboxyl group.
Describe the test for proteins.
The Biuret test, add the sample to Biuret solution and if a protein is present there will be a colour change from blue to purple.
What is the primary structure of a protein?
The sequence of amino acids that make up a polypeptide chain, peptide bonds join the amino acids together due to condensation reactions.
What is the secondary structure of a protein?
The sequence of amino acids in the polypeptide chain causes the chain to coil to produce an alpha helix or fold to produce a beta pleated sheet. Hydrogen bonds form between the amino and carboxyl groups in the amino acids.
What is the tertiary structure of a protein?
Further folding occurs to form a unique and precise 3D shape. Hydrogen and ionic bonds and disulphide bridges (Only when the R group contains sulphur) form between the R groups of different amino acids in the polypeptide chain. This is the final shape if the protein is only made of one polypeptide.
What is the quaternary structure of a protein?
It is made of more than one polypeptide chain, these different chains are held together by hydrogen bonds, ionic bonds or disulphide bridges. These bonds form between R groups on different chains.
What can affect the tertiary structure of a protein?
The sequence of amino acids will cause a change in the primary structure so the polypeptide chain formed will be different resulting in a change in the tertiary structure.
Temperature, because when the temperature gets too high it can break the bonds (Hydrogen, Ionic, Disulphide bridges) holding the tertiary structure together.
If the pH is too high or too low it can break the hydrogen and ionic bonds holding both the secondary and tertiary structure together, which will change the shape of the protein.
