15. Proteins

Question 1

What is protein denturation?

Answer 1

• When the protein denature it loses its function, e.g. enzymes loser their activity because the substrate can no bind to the active site
• Denaturation involves the disruption of the bonds holding the protein together by losing the tertiary, quaternary and secondary structures.

Question 2

Structure of proteins

Answer 2

Proteins are biological polymers composed of amino acids . Amino acids, linked together by peptide bonds, form a polypeptide chain. One or more polypeptide chains twisted into a 3-D shape form a protein. Proteins have complex shapes that include various folds, loops, and curves. Folding in proteins happens spontaneously. Chemical bonding between portions of the polypeptide chain aid in holding the protein together and giving it its shape.

Question 3

Secundary structure

Answer 3

refers to the coiling or folding of a polypeptide chain that gives the protein its 3-D shape. There are two types of secondary structures observed in proteins. One type is the alpha (α) helix structure (coiling). The second type of secondary structure in proteins is the beta (β) pleated sheet.

Question 4

Tertiary structure

Answer 4

refers to the comprehensive 3-D structure of the polypeptide chain of a protein. There are several types of bonds and forces that hold a protein in its tertiary structure.

Question 5

Which bonds are found in the tertiary structure?

Answer 5

• Hydrophobic interactions between non-polar side chains
• Hydrogen bonding between polar side chains
• Ionic bonding can occur between the positively and negatively charged side groups
• Disulfide bridge between sulphur atoms in cysteine