3.1.4.1 General properties of proteins Flashcards
What are the monomers from which proteins are made?
Amino acids
What is the general structure of an amino acid?
A central carbon bonded to an amine group NH2 a carboxyl group COOH a hydrogen atom and an R group side chain
What part of an amino acid differs between the twenty amino acids common in all organisms?
The R group side chain
What type of reaction forms a peptide bond between two amino acids?
Condensation reaction
What is a dipeptide?
A molecule formed by the condensation of two amino acids with a peptide bond
What is a polypeptide?
A polymer formed by the condensation of many amino acids with peptide bonds
What is a functional protein?
A protein that contains one or more polypeptides and is folded into a specific shape
What type of bond forms between oppositely charged R groups in proteins?
Ionic bonds
What type of bond forms between sulfur atoms in R groups of cysteine amino acids?
Disulfide bridges
What type of bond forms between partially charged atoms in the protein structure?
Hydrogen bonds
What is the primary structure of a protein?
The sequence of amino acids in a polypeptide chain held by peptide bonds
What is the secondary structure of a protein?
Folding of the polypeptide into alpha helices and beta pleated sheets held by hydrogen bonds
What is the tertiary structure of a protein?
Further folding of the polypeptide into a specific 3D shape held by hydrogen bonds ionic bonds and disulfide bridges
What is the quaternary structure of a protein?
The association of two or more polypeptide chains held by bonds such as hydrogen bonds and disulfide bridges
What is the test for proteins?
The biuret test
Describe the biuret test for proteins.
Add biuret reagent if protein is present a purple colour appears
What determines the function of a protein?
Its specific 3D shape determined by the sequence of amino acids in the primary structure
Why is the primary structure important for protein function?
It determines the specific 3D shape of the protein which is essential for its function
How does protein structure relate to its properties?
The specific folding of a protein determines its solubility stability and interaction with other molecules affecting its function
Protein - Protein Structure (7)
- Polymer of amino acids;
- Joined by peptide bonds;
- Formed by condensation;
- Primary structure is order of amino acids;
- Secondary structure is folding of polypeptide chain due to hydrogen bonding; (into alpha helix or beta pleated sheet)
- Tertiary structure is 3-D folding due to hydrogen bonding and ionic/disulphide bonds between R groups;
- Quaternary structure is more than one polypeptide chains;
Test for a protein
- Add Biuret reagent to the sample (1);
- colour change to lilac (1) (or lilac band appears
