Amino Acids, Peptides, Proteins, and Enzymes

Flashcards covering key concepts related to amino acids, peptides, proteins, and enzymes based on lecture notes.

Amino Acids

Organic molecules that serve as the building blocks of proteins.

Essential Amino Acids

Amino acids that the body cannot synthesize and must be obtained from the diet.

Non-Essential Amino Acids

Amino acids that can be synthesized by the body whenever needed.

Zwitterion

A molecule that has both a positive and a negative charge.

Peptide Bond

Covalent bonds formed between the carboxyl group of one amino acid and the amino group of another.

Dipeptide

A peptide consisting of two amino acids linked by a peptide bond.

Oligopeptide

A peptide consisting of 3 to 20 amino acids.

Polypeptide

A longer chain of amino acids typically longer than 20 amino acids that folds into a specific 3D structure.

Holoenzyme

The complete and catalytically active form of an enzyme.

Apoenzyme

An inactive enzyme that becomes active only when bound to a cofactor.

Active Site

The specific region on an enzyme where the substrate fits and undergoes catalysis.

Cofactors

Chemical species that bind to enzymes and are required for their biological activity.

Allosteric Enzyme

A regulatory enzyme whose activity is affected by the binding of other molecules.

Competitive Inhibition

A type of inhibition where an inhibitor competes with the substrate for the active site of the enzyme.

Non-competitive Inhibition

A type of inhibition where an inhibitor binds to the enzyme regardless of whether the substrate is bound.

Michaelis-Menten Kinetics

A model that describes the rate of enzymatic reactions by relating reaction rate to substrate concentration.

Km (Michaelis Constant)

The substrate concentration at which the reaction velocity is half of Vmax.

Vmax (Maximum Velocity)

The maximum rate of an enzymatic reaction when the enzyme's active sites are saturated with substrate.

Post-Translational Modifications (PTMs)

Chemical changes that proteins undergo after translation, affecting their function and regulation.

Proteolytic Cleavage

The process of breaking peptide bonds in proteins, resulting in either degradation or activation of proteins.

Phosphorylation

The addition of a phosphate group to a protein, which typically regulates its activity.

Coenzyme

An organic non-protein compound that binds to an enzyme to facilitate its catalytic function.

Primary Structure

The linear sequence of amino acids in a polypeptide chain, held together by peptide bonds.

Secondary Structure

Localized spatial arrangements of the polypeptide backbone, such as \alpha-helices and \beta-pleated sheets.

Tertiary Structure

The overall three-dimensional shape of a single polypeptide molecule, stabilized by various interactions between R-groups.

Quaternary Structure

The arrangement and interaction of multiple polypeptide chains (subunits) in a multi-subunit protein complex.

Denaturation

A process in which proteins loses its quaternary, tertiary, and secondary structure due to external stress or compounds, such as heat or pH changes.

Substrate

The specific molecule upon which an enzyme acts to facilitate a chemical reaction.

Enzyme-Substrate (ES) Complex

A temporary intermediate formed when an enzyme binds to its substrate at the active site.

Induced Fit Model

A model of enzyme action suggesting that the active site is flexible and changes shape to fit the substrate more securely upon binding.

Isoenzymes (Isozymes)

Different forms of the same enzyme that catalyze the same reaction but may have different amino acid sequences