Proteins Flashcards
How many amino acids are naturally occouring in proteins?
20
What are the 4 main parts of an amino acid?
The amine group-N-H-H
The carboxyl group- C=O- OH
The R group
The hydrogen atom
What is the bond that amino acids form and how?
A peptide bond by a condensation reaction, removing a molecule of water. An OH group from the carboxyl group of one amino acid and a H atom from the other amino acid joins to form water
What is a dipeptide?
2 amino acids bonded together by a peptide bond from a condensation reaction.
What is a polypeptide?
3 or more amino acids bonded together by peptide bonds from a condensation reaction
Whats the difference between a polypeptide and a protein?
In order to be classed as a protein, the polypeptide has to be folded into its 3 dimensional shape
What is meant by the primary structure of a protein?
The sequence of amino acids in a polypeptide, this is important because it helps determine the final structure of the protein, and therefore the function
What is meant by the secondary structure of a protein?
The linked amino acids that make up a polypeptide possesses both -NH groups and -C=O groups on either side, and because the hydrogen of the first group has a positive charge and the 0 on the second group has a negative charge these attract each-other forming weak
hydrogen bonds which causes the polypeptide chain which forms its 3 D shape and structure, which is called the a helix.
What is meant by the tertiary structure of a protein?
When the a helix of the secondary structure protein can be twisted and folded to give the complex structure of the protein which is known as the tertiary structure.
What is meant by the quatenary structure of a protein?
Large molecules often form compex molecules containing a number of polypeptide chains linked in different ways. It shows how individual subunits are arranged to form a larger 3D structure.
What are the bonds that hold together tertiary structure proteins called?
Ionic bonds- Formed between carboxyl and amine groups that are not involved in forming peptide bonds, they are weaker than disulfide bonds and are easily broken by changes in PH
Disulfide bonds- Strong and not easily broken bonds
Hydrogen bonds- Numerous bonds but not easily broken
How do we test for proteins?
Place a sample of our solution to be tested into a test tube and we add an equal volume of NaOH solution at room temperature. Then we add a few drops of very dilute copper II plus solution and mix gently. A purple colouration indicates a polypeptide bond, hence a protein.
Describe how the structure of a protein depends on the amino acids it contains
The primary structure of a protein is the sequence of amino acids in the polypeptide chain, and the hydrogen bonds between these result in the secondary structure of a protein which is an alpha helix structure, then due to interactions between R groups such as ionic bonds and disulfide bridges the tertiary structure if formed which creates the active site in enzymes, then the quatenary structure contains multiple of the polypeptide chains
How does an enzymes active site create a high rate of reaction?
It lowers the activation energy, and the induced fit causes the active site to change shape so the enzyme substrate complex causes bonds to form or break
Describe 3 ways dipeptides are similar
All have COOH on end and all have NH4 group on end , and all have 2 R groups
