Biochemistry: Protein Structure Quiz

Proteins, Amino Acids, Peptides

• Proteins are high-molecular weight organic substances, a fundamental component of all cells.
• Proteins are composed of amino acids.
• Proteins are broken down into amino acids during digestion.
• Amino acids are the building blocks of proteins.
• The sequence of amino acids determines the protein's structure and function.
• Living organisms synthesize proteins from the 20 amino acids.

Amino Acids

• They are organic derivatives of carboxylic acids, which minimally contain one amino group.
• Amino acids are coded in the genetic material.
• There are 20 common amino acids.

Properties

• Amphoteric (both acidic and basic character).
• The isoelectric point (pI) is the pH at which the molecule's net charge is zero.
• The pI of an amino acid is determined using the number of amino and carboxyl groups.

Peptides

• A peptide is formed when two amino acids bind together in a reaction that involves the removal of a water molecule.
• The amino acid that begins the chain is the N-terminal amino acid.
• The amino acid at the end of the chain is the C-terminal amino acid.
• Different combinations of amino acids form different peptides with different functions.

Important Peptides

• Hormones (e.g., insulin, oxytocin)
• Antibiotics (e.g., actinomycin)
• Many animal and plant toxins are peptides.

Proteins

• Proteins can be solid crystals, fibers, or colloids.
• They may dissolve in weak acids or bases.
• They are large molecules.

Protein Structure

• Primary: The linear sequence of amino acids.
• Secondary: Geometric structure of the peptide chain (alpha helix and beta pleated sheet).
• Tertiary: 3-dimensional structure of proteins, and the way polypeptide chains are folded. Two types of protein structure: globular and fibrillar.
• Quaternary: If the protein is aggregated of multiple protein subunits.

Protein Functions

• Structural: Support and shape.
• Hormonal: Communication between cells.
• Chemical: Enzymes (catalysts of biochemical reactions).
• Transport: Movement of substances.
• Regulatory: Control of cell activities.
• Protective: Antibodies and blood clotting factors.
• Contractile: Muscle protein involved in functions.
• Storage: Temporary storage of minerals and substances.

Protein Classification

• Simple: only amino acids
• Conjugated: amino acids plus other organic or inorganic components. Examples of conjugated proteins: lipoproteins, glycoproteins, phosphoproteins, metalloproteins, and nucleoproteins.

Test your knowledge on the primary and complex structures of proteins, including amino acid properties and peptide formation. This quiz covers essential concepts such as the isoelectric point and the various levels of protein structure. Ideal for students studying biochemistry or related fields.