Enzymes and coenzymes

What is an enzyme?

,An enzyme is a biological catalyst that speeds up chemical reactions in living organisms.

How do enzymes speed up chemical reactions?,

Enzymes lower the activation energy required for a reaction to proceed.

What is the role of carbonic anhydrase?,

Carbonic anhydrase speeds up the conversion of CO2 and H2O into H2CO3.

What are the six classes of enzymes defined by IUBMB?,

Oxidoreductases, Transferases, Hydrolases, Lyases, Isomerases, Ligases.

What is an active site?,

An active site is the region of an enzyme where substrate binding and catalysis occur.

What interactions help bind the substrate to the enzyme?

,Hydrogen bonds, ionic bonds, Van der Waals forces, and hydrophobic interactions.

What is the induced-fit model?,

The induced-fit model suggests that the active site changes shape to fit the substrate.

What is a holoenzyme?

,A holoenzyme is an active enzyme with its cofactor, while an apoenzyme is an inactive enzyme without its cofactor.

What are cofactors?,

Cofactors are non-protein molecules or ions required for enzyme activity.

What are the three main types of cofactors?,

Metal ions, prosthetic groups, and coenzymes.

What is a coenzyme?,

A coenzyme is an organic molecule that assists enzymes, often derived from vitamins.

What is the function of NAD+ and FAD?,

They act as electron carriers in oxidation-reduction reactions.

What role does Coenzyme A play?,

Coenzyme A transfers acyl groups in metabolic pathways.

What factors affect enzyme activity?,

Temperature, pH, substrate concentration, enzyme concentration, and inhibitors.

What is the Michaelis-Menten equation?

,Vo = (Vmax [S]) / (Km + [S]).

What is Km (Michaelis constant)?,

Km represents the substrate concentration at which an enzyme operates at half its maximum velocity.

What does a high Km indicate?,

A high Km indicates low substrate affinity, meaning more substrate is needed for the reaction.

What is Vmax?,

Vmax is the maximum reaction velocity when the enzyme is saturated with substrate.

What is the Lineweaver-Burk plot used for?,

It is a double-reciprocal plot used to determine Km and Vmax and analyze enzyme inhibition.

What are the two main types of enzyme inhibitors?,

Competitive and non-competitive inhibitors.

How does a competitive inhibitor work?,

It competes with the substrate for the active site and increases Km without affecting Vmax.

How does a non-competitive inhibitor work?

,It binds to an allosteric site, reducing enzyme activity and lowering Vmax without affecting Km.

What is feedback inhibition?

,A regulatory mechanism where the end product of a pathway inhibits an earlier step in the pathway.

What is allosteric regulation?,

A process where enzyme activity is modulated by binding of an effector at a site other than the active site.

How does phosphorylation regulate enzyme activity?

,Kinases add phosphate groups to activate/inhibit enzymes, while phosphatases remove them.

How are enzymes used in clinical diagnostics?,

Enzymes like creatine kinase and lactate dehydrogenase help diagnose heart attacks.

What is lactate dehydrogenase (LDH) used for in clinical diagnostics?,

LDH levels can indicate tissue damage, such as myocardial infarction.

What is the role of ribonuclease?,

Ribonuclease catalyzes the degradation of RNA into smaller components.

What is the role of glutamine:oxaloacetate transaminase (GOT)?,

GOT is used in liver function tests to assess liver damage.

What is enzyme compartmentalization?

,Localization of enzymes in specific organelles to control metabolic pathways.

What are prosthetic groups?,

Cofactors that are tightly bound to the enzyme, often via covalent bonds.

What is the function of biotin as a coenzyme?,

Biotin carries CO2 in carboxylation reactions.

What is the significance of vitamin-derived coenzymes?,

They act as carriers of specific atoms or functional groups during enzymatic reactions.

What is the role of pyridoxal phosphate (PLP)?,

PLP is a coenzyme involved in amino acid metabolism.

What is the difference between reversible and irreversible enzyme inhibition?

,Reversible inhibitors bind non-covalently and can be removed, while irreversible inhibitors form strong covalent bonds with enzymes.

What is the significance of enzyme kinetics?,

It helps understand how enzymes function under different conditions and how inhibitors affect them.

What is the function of metal ion cofactors?,

They stabilize enzyme-substrate complexes and assist in catalysis.

What is the significance of Zn2+ in enzymes?

,Zn2+ is a cofactor for enzymes like carboxypeptidase and alcohol dehydrogenase.

How do enzymes exhibit specificity?

,Enzymes recognize specific substrates through unique active site interactions.

What is covalent catalysis?

,A mechanism where an enzyme forms a temporary covalent bond with its substrate during the reaction.

What is the significance of transition state stabilization?

,It lowers the energy barrier and speeds up enzymatic reactions.

How does enzyme structure influence function?

,The 3D conformation of an enzyme determines substrate binding and catalytic activity.

Why are enzymes crucial in metabolism?,

They control the rate of biochemical reactions and allow life-sustaining processes to occur efficiently.

What is the difference between lyases and ligases?,

Lyases break bonds without water, while ligases form bonds using ATP.

How does enzyme localization affect function?,

Enzymes are compartmentalized within organelles to regulate metabolic pathways.

What is the function of thiamine pyrophosphate (TPP)?,

TPP is a coenzyme in decarboxylation reactions, such as in the pyruvate dehydrogenase complex.

What is the role of flavoproteins?,

Flavoproteins contain FAD or FMN and participate in redox reactions in metabolism.

How does enzyme concentration affect reaction rates?,

Higher enzyme concentration increases reaction rates until substrate saturation is reached.

What is the function of glutathione peroxidase?,

Glutathione peroxidase protects cells from oxidative damage by reducing peroxides.

What is the function of isomerases?,

Isomerases catalyze the rearrangement of atoms within a molecule to form isomers.