Enzyme Structure and Function

Enzyme Structure and Function

• Enzymes are proteins that catalyze biochemical reactions, and their kinetics involve studying the rates at which they catalyze reactions.
• Irreversible inhibitors permanently deactivate enzymes, reducing effective enzyme concentration and Vmax.
• At low substrate concentrations, the reaction rate increases linearly with substrate concentration due to available enzyme active sites.
• At high substrate concentrations, the reaction rate approaches Vmax as all enzyme active sites become saturated with substrate.
• Km value reflects the enzyme's affinity for its substrate, with lower Km indicating higher substrate affinity.
• Competitive inhibitors increase Km, while noncompetitive inhibitors do not affect Km.
• Cooperativity occurs when substrate binding facilitates the binding of more substrates.

Amino Acids

• Serine (S), threonine (T), and tyrosine (Y) residues are often phosphorylated by kinases.
• Glycine is achiral and optically inactive, and can disrupt alpha helices due to its small size and flexibility.
• Proline disrupts alpha helices due to its inflexible secondary alpha-amino group.
• Cysteine forms disulfide bridges and has an R absolute configuration.
• Amino acids have different charges at different pH levels due to approximate pKa values for carboxylic acid (2) and amino groups (9).
• Neutral polar amino acids contain OH, S, or amide groups, while neutral non-polar amino acids have uncharged alkyl or aromatic side chains.

Protein Structure

• Primary structure describes the linear sequence of amino acids stabilized by peptide bonds.
• Secondary structure involves folding of a polypeptide into alpha helices and beta-pleated sheets due to backbone interactions.
• Tertiary structure is the further folding of a polypeptide due to R-group interactions, which can be disrupted by changing the pH surrounding the protein.
• Quaternary structure consists of the interactions between multiple polypeptides, and is also disrupted by pH changes.
• Disulfide bonds are found in the extracellular space and are affected by denaturation.

Cofactors and Coenzymes

• Cofactors can be inorganic ions or organic molecules, while coenzymes specifically refer to organic molecules carrying specific chemical groups.
• Cooperativity occurs when substrate binding facilitates further substrate binding, and is not explained by Michaelis-Menten kinetics.

Carbohydrates: Structure and Function

• Monosaccharides are simple sugars that serve as building blocks for more complex carbohydrates and are key energy sources in cellular respiration.
• Disaccharides include maltose, sucrose, lactose, and cellobiose.
• Polysaccharides include glycogen (energy storage in animals), starch (energy storage in plants), and cellulose (structural component in plant cell walls).