Proteins Flashcards
What monomer are proteins made up of?
Amino acids
Draw and label the general structure of an amino acid
- Central carbon with 4 different groups coming off.
- Amine group H2N
- Carboxyl group COOH
- R Group (the section that is different for all amino acids)
- Hydrogen
How are amino acids joined together? What is the name of the bond formed?
Amino acids are joined together via a condensation reaction. Water is removed and the peptide bond forms between OH of the carboxyl and the H of the amine group. Dipeptides are formed by the condensation of two amino acids. Polypeptides are formed by the condensation of many amino acids
Draw two amino acids joining together to form a peptide bond.
What are the 4 stages of structure in a protein?
Primary, secondary, tertiary and Quaternary.
Describe the primary structure of a protein
It is the order and number of amino acids in a sequence in a polypeptide chain.
Describe the secondary structure of a protein. Where are the bonds located?
The polypeptide chain becomes processed and is either twisted to form alpha helix or bent and folded to form beta pleated sheets.
These structures are held in place by hydrogen bonds that are formed between the C=O groups of the carboxyl group of one amino acid and the H in the amine group of another amino acid.
Describe the tertiary structure of a protein. Where are the bonds located?
The secondary structure is further folded to form a unique 3D shape which is held in place by ionic, hydrogen and disulphide bonds.
Ionic and disulphide bonds form between the R groups of different amino acids. Hydrogen bonds are formed between the C=O groups of the carboxyl group of one amino acid and the H in the amine group of another amino acid.
Why do disulphide bonds only occur sometimes in the tertiary structure of a protein?
There must be a sulfur in the R group for the bond to occur.
Describe the quaternary structure of a protein.
A protein made up of more than 1 polypeptide chain.
What occurs if a protein denatures in the tertiary stage?
The bond that holds the structure in shape breaks and therefore the unique 3D shape is lost and the unique active site shape is lost.
What are the conditions needed to denature a protein?
High temperature (too much kinetic energy)
Too high/low a pH (too many H+ or OH-
Why is the sequence of amino acids important in the primary structure? Give examples.
If even one amino acid in the sequence is different then it will cause the ionic/hydrogen/disulphide bonds to form in a different location. This results in a different 3D shape. This means enzymes will have a different shaped active site and will no longer function or function differently. Or carrier proteins could have a different shapes binding site which means molecules would no longer be complementary and cannot be transported across the membranes.
What might cause a change to the amino acid sequence?
Mutation.
