Proteins Flashcards
What does an amino acid consist of?
An amino consists of a central alpha carbon covalently linked to an amino group, a hydrogen atom, a carboxyl group, and a variable side chain.
How are amino acids linked together?
Amino acids are linked together by peptide bonds formed between the carboxyl group of one amino acid and the amino group of another amino acid by means of a condensation reaction, releasing 1 water molecule.
What is the definition of primary structure?
Primary structure refers to the number, sequence and type of amino acids in a linear polypeptide chain.
What determines the sequence of amino acids in the polypeptide chain?
The sequence of amino acids in a polypeptide chain depends on the sequence of nucleotide bases in the gene encoding the protein.
What is the definition of secondary structure?
Secondary structure refers to the folding of polypeptide chains into regular structures such as a-helices and b-pleated sheets
What are the bonds involved in secondary structure
Hydrogen bonds between the -CO group of a peptide bond on one amino acid and the -NH group of a peptide bond on another amino acid in the same polypeptide chain.
What is the definition of tertiary structure?
Tertiary structure involves the further folding of polypeptide chains into their unique globular conformation.
What are the bond involved in maintaining the tertiary structure?
4 types of bonds between R groups of amino acids in the same polypeptide chain:
1. Hydrogen bonds between polar R groups of amino acid residues
2. Ionic bonds between charged R groups of amino acid residues
3. Disulfide bonds between sulfhydryl R groups of cysteine residues
4. Hydrophobic interaction between non-polar R groups of amino acid residues
What is the definition of quaternary structure?
Quaternary structure refers to the arrangement of polypeptide subunits within a protein made up of more than one polypeptide chain.
What are the bonds involved in the quaternary structure?
Bonds involved between R groups of amino acids of different polypeptide chains:
1. Hydrogen bonds between polar R groups of amino acid residues
2. Ionic bonds between charged R groups of amino acid residues
3. Hydrophobic interaction between non-polar R groups of amino acid residues
4. disulfide bonds between sulfhydryl R groups of cysteine residues
Why is haemoglobin soluble?
The tertiary structure of haemoglobin is folded such that the bulk of the hydrophobic R groups of non-polar amino acids residues are buried in the interior of the globular structure while the hydrophilic R groups of polar and charged amino acid residues are on the surface of the globular structure.
How does high temperatures lead to denaturation of enzymes?
At high temperatures, protein molecules gain kinetic energy. Thermal agitation within the protein molecule disrupts the ionic, hydrogen bonds and hydrophobic interaction between R groups of amino acid residues which are involved in maintaining the tertiary structure of the protein. There is a loss of the specific conformation of the active site and the active site cannot bind to the substrate.
How does change in pH lead to denaturation of enzymes?
Change in pH values affect the concentration of H+ in the environment. This alters the ionic charge of acidic and basic amino acid residues, disrupting ionic and hydrogen bonds that maintain the specific 3d conformation of the active site and the active site cannot bind to the substrate.
