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Description
Flashcards by emma_moran, updated more than 1 year ago
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Created by emma_moran
over 10 years ago
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| Question | Answer |
| What are enzymes? | They are biological catalysts |
| What is the role of the enzyme papain? | It is found in papaya plants and will break any peptide bond- it is used to tenderise meat |
| What is the role of the enzyme trypsin? | It is a digestive enzyme that only splits bonds between lysine and arginine residues |
| What is the role of the enzyme thrombin? | Catalyses the hydrolysis of Arg-Gly only in a specific chain of residues |
| What often happens to the energy of the reactants in enzyme controlled reactions? | It is is converted into other forms e.g I mitochondria the free energy of small molecules is converted into the energy in an ion gradient |
| What is the active site of an enzyme? | The region that binds substrates and contains that directly participate in the making and breaking of bonds |
| What are the residues of the active site called and what do they do? | They are called the catalytic group and they promote the formation of the transition state. |
| How do substrates bind to the active site? | By multiple weak interactions including hydrogen bonds, Van der Waal's and electrostatic interactions. |
| How is it that only specific substrates bind to an active site? | The binding depends on the precisely defined arrangement of atoms in an active site. The R groups in an active site create regions that only appropriate chemical groups can bind to. |
| What is the lock and key model? | The active site and enzyme possess complementary shapes that fit together perfectly |
| What is the induced fit model? | The active site and substrate have similar shapes and the active site moulds around the substrate when they bind. |
| What are co-factors? | Simple inorganic metal ions that promote enzyme function |
| What are co-enzymes? | Small organic molecules that attach to activate the enzyme and detach when the reaction is complete to deactivate the enzyme. |
| What are apoenzymes? | An enzyme without its cofactor |
| What are haloenzymes? | Enzymes with their cofactors |
| What are isoenzymes? | Enzymes that differ in amino acid sequence but catalyse the same chemical reaction. |
| What different properties do isoenzymes usually display? | Different kinetic parameters (different KM values) or regulatory properties |
| What are the symptoms of Hurler syndrome? | Abnormal bone structure and developmental delay. |
| What causes Hurler syndrome? | Build up of glycosaminoglycans due to a deficiency of iduronidase- an enzyme responsible for the degradation of mucopolysaccharides in lysosomes. |
| What is the treatment for Hurler syndrome? | Enzyme replacement therapy and bone marrow replacement |
| What are the symptoms of Neimann-pick disease? | Cell death and the malfunction of major organ systems |
| What causes Neimann-pick disease? | Lack of aid sphingomyelinase (ASM)-an enzyme found in lysosomes that is required to metabolise a lipid call sphingomyelin. If ASM is absent, sphingomyelin can't be metabolised and accumulates in cells |
| What symptoms occur in Tay Sachs disease? | Progressive deterioration of nerve cells and of mental and physical abilities that commences at around six months of age and results in death at around age four. |
| What causes Tay Sachs disease? | Harmful quantities of cell membrane components known as gangliosides accumulate in the brains nerve cells, leading to premature death of cells |
| What are the symptoms of Homosystinuria? | Near sightedness, increased risk of blood clotting, brittle bones. Less common forms: Intellectual disability, failure to grow and gain weight, seizures and problems with movement. |
| What causes homosystinuria? | Inherited disorder which effects the enzyme Methylenetetrahydrofolate reductase (MTHFR) which converts homosysteine to methionine |
| How do enzymes effect the energy of enzyme controlled reactions? | They lower the energy required to initiate the conversion of the reactants into the products |
| Do enzymes alter the free energy difference between the products and reactants? | No the energy change remains the same |
| What is the activation energy? | The energy required to start a reaction |
| How do enzymes accelerate a reaction? | They increase the rate of reaction and not the reaction equilibrium |
| How do enzymes increase the rate of reaction? | They enable the formation of the transition state which has a higher energy level |
| What are oxidoreductases? | Enzymes that catalyse oxidation or reduction reactions, where electrons are transferred from one molecule to another |
| What are transferases? | Enzymes that catalyse the movement of a functional group from one molecule to another |
| What are lyases? | Enzymes that catalyse reaction that generate a double bond. This is a type of elimination reaction. |
| What are synthases? | They add a substrate to a double bond (opposite of lyases) |
| What are isomerases? | Enzymes that catalyse structural changes within a molecule. There is only one substrate and no product with nothing gained or lost, so they only represent a change in shape. |
| What are Ligases? | They are the catalyst of ligation; the joining of two substrates. Usually chemical energy is required so its is coupled with the hydrolysis of ATP. |
| What are hydrolases? | Enzymes that catalyse hydrolysis; breaking of bonds through the addition of water |
| What are helicases? | Enzymes that separate DNA strands |
| What are kinases? | Enzymes that transfer phosphate groups from molecules such as ATP to substrates |
| What factors effect the rate of enzymes controlled reactions? | Concentration of enzyme, concentration of substrate, temperature, pH, inhibitors |
| If you are increasing the concentration of the substrate what is the saturation point | The point where all active sites are occupied |
| If you are increasing enzyme concentration what is the saturation point? | There is no more substrate |
| What is the optimum enzyme temperature in the human body? | 37 |
| What is Vmax? | The maximum velocity achieved by a system at saturating substrate concentrations |
| What is Km? | The substrate concentration at which the reaction velocity is 50% of the Vmax |
| What does Km measure? | The affinity of an enzyme for its substrate |
| What does the value of Km represent? | The lower the value of Km the more tightly the substrate is bound. |
| What is Km often used to distinguish between? | Isoenzymes |
| What values of Vmax and Km would an efficient enzyme have? | High Vmax and low Km |
| Name two process in which the role of Km is important | Control of blood glucose level and the metabolism of alcohol (READ HOW BOTH OF THESE MECHANISMS WORK) |
| What is alcohol converted to by the body? | Acetaldehyde |
| What enzyme converts alcohol to acetaldehyde and vice versa? | Alcohol dehydrogenase |
| What are the two types of reversible inhibition? | Competitive and non-competitive |
| How do competitive inhibitors work? | They have a simuilar shape to the substrate which means they can also bind to the active site preventing the formation of enzyme substrate complexes. |
| What does the competitive inhibitor Disulfiram (Antabuse) inhibit? | Aldehyde oxidase- which causes the accumulation of acetaldehyde with subsequent side effects of nausea and vomiting |
| What are the symptoms of methanol poisoning and how are they caused? | Methanol is oxidised to formaldehyde and formic acid which attack the optic nerves and cause blindness. |
| How is methanol poisoning treated? | Ethanol is given as an antidote which competitively hibitits the oxidation of methanol and the oxidation of methanol is slowed down and the toxic by-products don't have a chance to accumulate. |
| How do non competitive inhibitors work? | The bind to an allosteric site on the enzyme and this causes the active site to change shape so the substrate can no longer fit. |
| What is Nifedipine used to treat? | Angina and high blood pressure |
| How does Nifedipine work? | It is a calcium channel blocker, it inhibits Ca2+ dependent ATPase which prevents the uptake of calcium into cardiac cells. |
| How do irreversible inhibitors work? | They bind so tightly to the active site that they can't be removed |
| What do MAOIs do? | They are chemicals that inhibit the activity of the monoamine oxidase family. |
| What are MAOIs often used to treat? | Depression |
| What happens if MAOIs are ingested orally? | They inhibit the catabolism of dietary amines |
| How does uncompetitive inhibition work? | The inhibitor increase the enzyme's affinity for the substrate (Km is lowered) which means its takes longer for the product to leave the active site (Vmax decrease) |
| How do end product inhibitors work? | The enzyme makes something to switch another on off |
| What are zymogen? | An inactive precursor of the enzyme. A zymogen is typically a longer polypeptide that must be hydrolysed at a specific location for the active form of the enzyme to be produced. |
| What is proteolysis? | Fusion of a protein with a lysosome |
| How are enzymes used as cardiac biomarkers? | Elevations of cardiac enzyme levels should be interpreted in the context of clinical and ECG findings |
| What is troponin? | Contractile protein that normally is not found in serum. It is only released when myocardial necrosis occurs |
| How does ELISA work? | Antigens from the sample are attached to a surface. Then, a further specific antibody is applied over the surface so it can bind to the antigen. This antibody is linked to an enzyme, and, in the final step, a substance containing the enzyme's substrate is added. The subsequent reaction produces a detectable signal, most commonly a color change in the substrate. |
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