Proteins Flashcards
What are the monomers of proteins?
Amino acids.
What is a dipeptide?
A molecule that is formed when two amino acids join together.
What is a polypeptide?
A molecule that is formed when more than two amino acids join together.
What are proteins made up of?
One or more polypeptides.
What is the general structure of an amino acid?
A carboxyl group (-COOH).
An amine group (-NH2)
An R group (variable side group).
How many amino acids are there in total?
20.
What reaction links amino acids?
Condensation reaction to form dipeptides or polypeptides.
What is released when amino acids join together?
A molecule of water.
What type of bonds form between amino acids?
Peptide bonds.
What reaction occurs when dipeptides and peptides are broken down?
Hydrolysis reaction.
What are the 4 levels of a protein’s structure?
Primary.
Secondary.
Tertiary.
Quaternary.
What is the primary structure of a protein?
The sequence of amino acids in the polypeptide chain.
What bonds form between the amino acids in the chain to form the secondary structure of a protein?
Hydrogen bonds.
What do the hydrogen bonds in the secondary structure cause to happen?
The chain coils into an alpha helix, or folds into a beta pleated sheet.
What happens in the tertiary structure of a protein?
The coiled or folded chain or amino acids is coiled and folded further.
What forms between different parts of the chain in the tertiary structure?
More bonds form, including hydrogen bonds and ionic bonds.
What happens when two molecules of cysteine come close together in the tertiary structure of a protein?
Disulphide bridges form - the sulphur atom in one cysteine bonds to the sulphur atom in the other.
For what type of proteins is the tertiary structure the final 3D structure?
Proteins made from a single polypeptide chain.
What is the quaternary structure of a protein.
The way multiple polypeptide chains are assembled together.
For what type of proteins is the quaternary structure the final 3D structure?
For proteins made from more than one polypeptide chain.
What is the test for proteins?
The Biuret Test.
How do you carry out the biuret test for proteins?
The test solution needs to be alkaline, so first you add a few drops of sodium hydroxide solution.
Then you add some copper sulphate solution.
What is a positive result of the biuret test?
If protein is present, the solution turns purple. If there is no protein present, it will stay blue.
