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X-Phar410
Enzymes Part I
| Question | Answer |
|---|---|
| In equilibrium the reaction is not stopped | the concentrations just become constant |
| Keq= | [product]/ [reactant] |
| if one arrow is larger in an eq rxn, the larger arrow denoted | the more favorable direction of the reaction |
| if arrow on top is larger pointing to right, the [product]/ [reactant] will be | greater than 1 |
| if equilibrium arrow on bottom is larger in favor of the left side of the reaction the [product]/ [reactant] will be | less than 1 because rxn favors left side |
| if Keq is >1, delta G will be | negative; if delta G is positive, the reaction has no tendency to go forward (concentration of products higher than reactants) |
| if delta G is positive, the reactants are | in higher concentration; Keq < 1 |
| Enzymes are typically | globular proteins; speed rxn by lowering AE |
| For a rxn that is zero order, the velocity doesn't depend on concentration of substrate | no answer |
| small molecule required for enzyme activity; organic or inorganic; tight or loose | cofactor |
| ORGANIC; LOOSELY bound enzyme, like a substrate | coenzyme- Ex: NADP(H), NAD(H), ATP |
| organic or inorganic cofactor that is TIGHTLY bound to enzyme | prosthetic group. Ex: Heme, iron- sulfur clusters, metal ions |
| folded polypeptide chain of a cnjugated protein | apoprotein |
| complete, biologically active protein conjugate, consisting of folded polypeptide chains and relevant cofactors | holoprotein |
| as temp increases, kinetic energy of molecules increase including substrate | how heat affects proteins |
| Temperature increase affects reaction rates of proetin denaturing until | max level is achieved then it drops off with further increase in temp |
| most animal proteins denature at | 40 degrees; optimal is 37 degrees |
| pH can cause enzyme to perform better or worse depending on | R group; if outside pH range the protein will denature; cause a configuration change |
| region of an enzyme that accepts substrate (and cofactors); contributes catalytic residues that directly participate in making/ breaking of bonds | active site |
| active site is 3D and dynamic | also takes up a small are and is usually a cleft or crevice |
| substrates are bound to active sites by | non-covalent bonds |
| active site is specifically catered to a specific molecule | no answer |
| If an enzyme has 5 active sites and all are filled with substrates it is | saturated |
| Enzymes ability to reduce delta G | entropy reduction; acid- base catalysis; covalent catalysis |
| one or more substrates bind in active site with correct orientation | Entropy reduction- "S"; disorder |
| some enzymes can have multiple active sites | true |
| Substrate protons important for reactivity are accepted or donated by amino acid in the active site | General acid- base catalysis; structural mechanism for delta G reduction; accounts for pH dependence of enzyme activity |
| transient (brief) covalent bond is formed between enzyme and substrate- usually for cleavage | Covalent catalysis; delta G reduction |
| 6 classes of enzyme reactions | oxidoreductase; transferase; hydrolase; lyase; isomerase; ligase/synthetase |
| Enzyme reactions:catalyze oxidation/reduction reactions, transfer electrons from one compound to another, thus changing the oxidation state of both substrates. | Oxidoreductases:dehydrogenases (transfer H-); oxygenases (oxidizes with O2); peroxidases (i.e. catalase) |
| Enzyme reactions:catalyze reactions in which a functional group is transferred from one compound to another | Transferases; (kinases; adds phosphate group, ATP is source of phosphate) |
| Enzyme reactions:cleave carbon-oxygen, carbon-nitrogen, or carbon-sulfur bonds by adding water across the bond. | Hydrolases |
| the equation describes the relationship between rate, substrate, and Michaelis constant so the lower the Km value the higher the affinity for enzyme toward substrate (look at the graph) | MM MM notes |
| more specific indicator of liver inflammation than AST | ALT; found predominately in the liver |
| if AST high and ALT normal, there is likely damage to | organ other than liver |
| cleaves C-O, C-N, or C-S bonds by adding water across bond | Hydrolases |
| normal AST level | 7-27 |
| normal ALT level | 1-21 |
| ALT is more specific and AST may also be elevated in | heart or muscles in MI or pancreatitis |
| too much tylenol or drinking | ALT and AST levels both high |
| Maltose --> Glucose with Maltase enzyme | hydrolase |
| Cleaves C-O, C-N, or C-S WITHOUT addition of water AND without oxidizing or reducing substrates | Lyases; water can be a produt but not used to break hydrate the molecule |
| catalyze intramolecular rearrangements of functional groups that reversibly interconvert optical or geometric isomers | Isomerases |
| catalyze formation of new chemical bonds by coupling their formation to the cleavage of a high-energy compound | Ligases/Synthetases;Ligases differ from lyases in that they utilize the energy obtained from cleavage of a high-energy bond to drive the reaction usually ATP. |
| Enzymes that catalyze the same reaction, but differ in structure or sequence are called | isoenzymes(isozymes) Ex: lactate dehydrogenase. May also have different reaction rates/tissue distributions. They usually share the same name and are differentiated by the addition of letters or numbers (i.e. LDH1, LDH2, LDH3, etc.) |
| direct, reversible inhibition at an enzyme’s active site by the product of the enzyme-catalyzed reaction | Product inhibition; simplest form of enzyme regulation |
| Products can often weakly inhibit the enzymes that produced them because | reactant and product are similar in structure and can compete for binding site |
| simplest form of enzyme regulation | product inhibition |
| Allosteric regulators bind enzyme at a location distinct from the active site | this can increase or decrease enzyme activity because it changes the conformation of the protein |
| when a downstream product inhibits an upstream enzyme | feedback inhibition |
| phosphorylation reults in conformational changes that | can increase or decrese an anzymes catalytic activity |
| protein phosphatases do what | remove phosphate group from enzyme |
| a large inactive form of an enzyme that can be activated by proteolytic cleavage | zymogen; ex: digestive enzymes are synthesized as zymogens which can be activated on demand by proteases. |
| Pancreatitis is causes by premature activation of digestive zymogens | they end up digesting pancreatic tissue |
| Enzyme synthesis and deradation | form of regulation that occurs over hours to days |
| Vmax is proportional to the amount of enzymes present | amount of enzyme generated can be increased or decreased based on physiological needs; ex, insulin can induce synthesis of an enzyme |
| Mechanisms of Enzyme regulation (6) | product inhibition; allosteric regulation; covalent modification; protein-protein regulation; zymogen cleavage; enzyme synthesis and degradation |
| Damaged cells can release ____when diseased | isoenzymes; normally in the cell but are released into the blood |
| Following an acute cell damage (like heart attack) it takes how long for enzyme levels to spike? | 18-36 hours; in chronic disease, like cancer, blood enzymes are elevated |
| most common enzymes used to diagnose MI are | CK (creatine phosphokinase) and LDL (lactate dehydrogenase) |
| Three isozymes of Cystolic CK | CK-BB; CK-MB; and CK-MM each made of two polypeptides (M or B) |
| CK-BB isozyme is usually seen where? | In the brain |
| The CK-MM isozyme is usually seen where? | Skeletal muscle; also in heart muscle |
| Which CK isozyme is more predominant in the heart? | CK-MB |
| Baseline CK activity in the plasma is usually | 95% CK-MM |
| Two plasma CK assays are useful in diagnosing heart attack | Total Ck activity; if elevated could mean heart attack or some other muscle damaging disorder. If CK-MB is high then we know there is a heart prob |
| Heart attack = elevated CK-MB levels | no answer |
| Elevated LDL1 is indicative of what? | heart attack; LDL2 is normally higher but if LDL1 level surpasses it (levels are 'flipped') there is heart attack; |
| Total LDL elevation OTHER than the "flip" scenaario indicate what? | damage or disease in a tissue other than the heart |
| AST indicates what | liver damage; ALT also indicates but is more specific |
| ALP (not as frequent as ALT or AST) | congestion of bile tract; GGT can also indicate this but is more specific to liver |
| GGT (not as frequent as AST or ALT) | congestion of bile tract and or liver damage; more specific to the liver that ALP |
| Can dissolve a clot in an emergency; not used as maintenance med; therapuetic enzyme | Streptokinase (streptase) |
| Reduce the size of a thrombus after a heart attack | Tissue Plasminogen Activator |
| starves and kills acute lymphoblatic leukemia (ALL) cells | Asparaginase (Elspar) |
| Catalyses conversion of dietary lactose to galactose and glucose | Lactase (Lactaid);undigested lactose is bacterially fermented in intestines, produces gas; enzymes from Aspergillis fungi |
Created by:
angieryx
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