Questions and Answers
What is the composition of an enzyme?
What is the primary function of enzymes in the body?
What is the role of a coenzyme in an enzyme-catalyzed reaction?
What is the term for the site on an enzyme where interaction with the substrate takes place?
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What is the term for the protein part of an enzyme?
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What is the characteristic of enzymes that allows them to act upon specific substrates?
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What is the name of the enzyme that catalyzes the hydrolysis of peptide bonds in proteins?
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Which of the following is an example of an exoenzyme?
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What type of enzyme catalyzes the breakage of bonds without catalysis?
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What is the optimum pH range for most enzyme activity?
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What is the term for the active form of an enzyme?
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What is the term for an enzyme that consists of a protein and a non-protein component?
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What is the role of enzymes in muscle contraction?
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What is the International Union of Biochemistry (IUB) responsible for?
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What type of enzyme catalyzes the formation of an isomer of a compound?
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What is the characteristic of enzymes that allows them to be effective in small quantities?
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Study Notes
Enzymes
- Enzymes are proteins that act as catalysts, speeding up chemical reactions without undergoing any change themselves.
- All enzymes are proteins, but not all proteins are enzymes.
- Enzymes are required in very small quantities.
- Each enzyme is very specific and only attaches to one type of molecule, known as its substrate.
- Enzymes possess an active site, where interaction with the substrate takes place.
Properties of Enzymes
- Catalytic property: a small amount of enzyme is enough to break large molecules down into smaller molecules.
- Specificity: enzymes are very specific in action, with one enzyme acting only on a particular substrate.
- Reversibility: most reactions catalyzed by enzymes are reversible.
- Sensitivity to temperature: enzymes are thermolabile or very sensitive to heat and temperature.
- Specificity to pH: enzymes show maximum activity at an optimum pH of 6-8.
Functions of Enzymes
- Essential for respiration, digestion of food, DNA replication, muscle contraction, and nerve function.
- Store and release energy (ATP).
- Create larger molecules from smaller ones.
- Hormone production.
- Transporting materials around a cell.
Sources of Enzymes
- Endoenzymes: function within cells, most enzymes are this type. Example: metabolic oxidase.
- Exoenzymes: liberated by cells and catalyze reactions outside the cell. Examples: digestive enzymes (amylase, lipase, protease).
Chemical Composition of Enzymes
- Enzymes may consist of:
- Protein only. Examples: pepsin, trypsin.
- Conjugated protein (holoenzyme), consisting of:
- Protein + Co-Enzyme.
- Protein + prosthetic group.
- Protein + metal.
Coenzymes and Cofactors
- Coenzymes: organic non-protein molecules that bind to the enzyme and participate in the reaction by carrying electrons or hydrogen atoms.
- Cofactors: non-proteinous substances that associate with enzymes and are essential for their functioning.
- Holoenzyme: consists of Apoenzyme + prosthetic group.
- Apoenzyme: the protein part of the enzyme.
- Prosthetic groups: cofactors tightly bound to an enzyme at all times. Example: FAD.
Zymogen and Enzyme Nomenclature
- Zymogen: the inactive form of an enzyme. Example: pepsinogen → HCl → pepsin (active).
- Enzyme nomenclature:
- Trivial name: such as trypsin and pepsin.
- Adding suffix "ase" to the substrate, such as maltase and lactase.
- International Union of Biochemistry (IUB) systematic name, indicating:
- Substrate acted upon.
- Coenzyme involved in the reaction.
- Type of reaction catalyzed.
Classification of Enzymes
- Oxidoreductases: catalyze oxidation and reduction reactions. Example: pyruvate dehydrogenase.
- Isomerases: catalyze the formation of an isomer of a compound.
- Transferases: catalyze the transfer of a chemical group from one to another compound. Example: transaminase.
- Hydrolases: catalyze the hydrolysis of a bond. Example: pepsin.
- Lyases: catalyze the breakage of bonds without hydrolysis. Example: aldolase.
- Ligases: catalyze the joining of two molecules. Example: DNA ligase.
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Description
This quiz covers the components of enzymes, including proteins, metals, coenzymes, cofactors, apoenzymes, and prosthetic groups. Learn about the roles of each component in enzyme function.
