4. Protein Structure

Question 1

What are amino acids?

Answer 1

Proteins are made from a specific sequence of amino acids. There are 20 different types of Amino Acids. Amino Acids have three distinct chemical groups: Hydrogen, Carboxyl and R-Group.

Question 2

What is the primary structure of proteins?

Answer 2

• Amino acids are joined by peptide bonds.
• Many amino acids are joined together to form a polypeptide chain.
• The sequence of amino acids is called the primary structure.

Question 3

What is the secondary structure of proteins?

Answer 3

• Polypeptide molecules twist into a helix or folded shape.
• The shape is stabilized by hydrogen bonds between peptide groups.
• The pleating of the polypeptide chains due to hydrogen bonding is called secondary structure.

Question 4

What is the Tertiary structure of proteins?

Answer 4

• Polypeptide chains fold into unique 3D shapes.
• The pleating of the polypeptide chain due to attractions and repulsions between non adjacent amino acid side chains (R groups) is called tertiary structure.
• The tertiary function of a polypeptide is related to its biological function.
• The nature of attractive forces is dependent on the chemical structure of the R groups and includes hydrogen bonding, ionic bonding, covalent bonding and hydrophobic interactions.
• Disulphide bonds are covalent linkages between sulfur containing side chains of cyteines (aa) and are very strong helping to stabilize the tertiary structure

Question 5

What is the quarternary structure of proteins?

Answer 5

• Some proteins are composed of more than one polypeptide molecule.
• The arrangement of the folded polypeptide subunits is called quaternary structure.

Question 6

Why is the 3D shape of proteins critical?

Answer 6

The shape of the protein is complementary to the shape of its target molecule. Meaning that the two molecules interact with high specificity. Will determine its specific function.

Question 7

What are Enzymes?

Answer 7

• Catalysts that speed up chemical reactions in cells by binding to target molecules (substrates)
• The shape of the enzyme is complementary to the shape of the substrate.

Question 8

What are Peptide Hormones?

Answer 8

• Hormones regulate physiology and behaviour in a multicellular organism by facilitating communication between cells.
• Hormones are released from endocrine glands and travel in the circulatory system to target cells.
• Examples include: insulin, glucagon, and ADH
• The hormones bind to receptor proteins in the membrane and cytoplasm of target cells. The shape of the receptor protein is complementary to the shape of the hormone.

Question 9

What are Antibodies?

Answer 9

• Provide protection against pathogens by binding to and neutralizing molecules called antigens found on the surface of pathogens.
• The shape of an antibody is complementary to the shape of an antigen.