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Biochem-Enzymes
Med’11 Biochemistry Enzymes
| Question | Answer |
|---|---|
| What are enzymes? | Biological catalysts They permit reactions to “go” at conditions that the body can tolerate and can process millions of molecules every second They are very specific – react with one or only a few types of molecules (substrates) |
| How do enzymes increase the reaction rates? | By providing an alternate, easier pathway for a reaction and lowering activation energy barrier |
| What is the transition state? | Unstable arrangement of atoms in which chemical bonds are in the process of being formed or broken |
| Define activation energy. | The energy required to reach the transition state from the ground state of the reactants |
| Formation of ES (raises/lessens) energy of S by bringing reactants together? | Raises |
| Enzymes _____ the transition state. | Stabilize |
| What is a prosthetic group? | Coenzyme or cofactor covalently linked or bound non-covalently very tightly to an enzyme |
| What is a substrate? | The molecule acted upon by the enzyme to form product |
| What is the product? | The substance that is produced by the action of the enzyme |
| What is an apoenzyme? | The protein portion of the enzyme which is catalytically inactive |
| What is a coenzyme? | An additional component to the enzyme to function properly . Organic or organo-metallic molecule that assists an enzyme |
| What is a cofactor? | An additional component to the enzyme to function properly Usually a metal ion or small organic molecule that is needed to activate the apoenzyme |
| What is an active site? | A particular arrangement of amino acids side-chain in the polypeptide, specific to bind a specific substrate, also contains the machinery involved in catalyzing the reaction |
| True or False: Enzymes are huge proteins, and all of the enzyme is used in the reaction. | False - Only a small part is involved in the reaction |
| What are the 2 components of the active site? | Binding Site Catalytic Site |
| Enzymes are biological catalysts. They increase the rate of chemical reactions by: A. Raising the activation energy B. Temporarily increasing the temperature C. Covalently binding the substrate D. Lowering the activation energy | D Lowering the activation energy |
| What is a holoenzyme? | Holoenzyme: The apoenzyme + cofactor or prosthetic group |
| What is a proenzyme (zymogen)? | inactive precursor form of some enzymes (e.g. many digestive enzymes) that will be activated by cleavage of a specific peptide in its structure |
| What is an allosteric site? | A region of enzyme molecules (not at the active site) where small molecules bind & effect a change in the activity of the active site by change in the conformation of the enzyme. |
| Compare between enzymes and inorganic catalysts their natures. | Enzymes: Proteins Inorganic Catalysts: Usually metals |
| Compare between enzymes and inorganic catalysts their effects of heat. | Enzymes: Heat labile Inorganic Catalysts: Heat stable |
| Compare between enzymes and inorganic catalysts their molecular weights. | Enzymes: High Inorganic Catalysts: Low |
| Compare between enzymes and inorganic catalysts their dialysis. | Enzymes: Non-dialysable Inorganic Catalysts: Dialyasble |
| Compare between enzymes and inorganic catalysts their reversibility. | Enzymes: Most reactions are reversible Inorganic Catalysts: Irreversible |
| Compare between enzymes and inorganic catalysts their specificity. | Enzymes: All highly specific Inorganic Catalysts: Non-specific |
| What is the nomenclature of enzymes based on? | How it reacts Add –ase ending |
| What is the basis of enzyme classification? | Based on type of reaction |
| What are the different classifications of enzymes? | Lyases break C-O, C-C or C-N bonds Isomerases rearrange functional groups Ligases join two molecules |
| What are the types of enzyme specificity? | Absolute -Reacts with a single substrate Relative (linkage) specificity-Catalyze a specific combination of bonds Group specificity-Work with similar molecules with the same functional grp Stereochemical specificity-Work with the proper D- or L |
| What is a ribozyme? | RNA enzyme |
| List the activities of ribozymes. | Cleavage and rejoining of oligonucleotide substrate Cleavage of DNA phosphodiester bonds Cleavage of RNA at sequence-specific sites Hydrolysis of esters Formation of peptide bonds between amino acid |
Created by:
Salma O
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