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Enzymes - Coggle Diagram
Enzymes
poison & drugs
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potassium cyanide
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Rasputin was poisoned with it but survived - had unusually low pH levels in stomach acid which may have reduced formation of hydrogen cyanide
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snake venom
contains lots of different enzymes & toxins, such as; (below)
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protease inhibitors
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amprenavir & ritonvair are protease inhibitors used to treat some viral infections - completely inhibit viral protease enzymes
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antibiotics
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e.g. Penicillin - inhibits enzyme transpeptidase, responsible for building cross bridges on walls of bacterial cells - without this enzyme the bacteria cannot build the cell wall & fall apart
bacterial resistance
resistance is cause by random mutation - sometimes these new mutation codes for a new substance which can destroy or inactive an antibody
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many strains of bacteria are resistant to penicillin cause they product enzyme beta-lactamase which breaks down the penicillin molecule
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ATPase inhibitors
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the chemicals in digitoxin are cardiac glycosides which inhibit the sodium potassium pump in cell membrane of heart muscle cells allowing more calcium to enter
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treating AIDs
normally HIV uses reverse transcriptase to make DNA from its RNA, which enters the nucleus of a host cell & controls it
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Enzymes & pH
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optimum pH = the concentration of H^+ ions which holds the active site of the enzyme on the correct shape
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Inactive precursors
you stomach wall releases the inactive precursor enzyme (pepsinogen) which when it meets HCL inside the stomach the low pH converts it into the active protease called pepsin
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in the small intestine it meets another enzyme called enterokinase which removes a portion of the molecule & changes trypsinogen into the active protease trypsin
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activation energy (Ae)
most reactions in living cells require input of energy before the molecules react = activation energy
enzymes lower the Ae needed to initiate a reaction by having the correct enzyme the rate of reaction is increased
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Enzyme structure
active site
temporary bonds form between the substrate molecule & the R group of the amino acids of the enzyme active site
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after enzyme -substrate complex is formed the enzyme catalyses the reaction to product an enzyme-product complex
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Cofactors - coenzymes, prosthetic groups & inorganic ion cofactors
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Coenzymes
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e.g. an enzyme may not work with a substrate unless a cofactor made from another reaction has been made & is now present
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will bind for a sort period to the active site either just before or at the same time as the substrate binds
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e.g. pyruvate dehydrogenase is an enzyme involved in respiration - it cannot work unless a coenzyme derived from vitamin B3 is present
Prosthetic groups
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e.g. diagram shoes part of enzyme carbonic anhydrase with prosthetic group containing zinc (blue), without it being a presently part of the molecule the enzyme wouldn't work - it contributes to the 3D shape of the protein
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inorganic ion cofactor
sometimes an addition of ions increases the enzyme activity - cause ions alter the charge of the enzyme or substrate & makes binding more easy
amylase breaks starch into maltose but works better if chloride ions are present & even better if calcium ions are present to stabilise the molecule
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how enzymes work
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Induced fit theory
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the tight fit puts a strain on the molecules & its bonds enabling them to react more easily - how enzymes lower the Ae of reactions which they catalyse
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Enzyme inhibition
enzyme inhibiters are substances that interfere with the functioning active sites & reduce its activity
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end-product inhibition
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eventually all the end product will be used by the cell & there will be less/no product to inhibit the 1st enzyme so production begins again
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where enzymes are found
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intracellular enzymes
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e.g. phagocytes engulf pathogens trapping them in phagocytic vacuoles which lysosomes fuse to & the pathogen is digested
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Endotherms & enzymes
Endotherms
advantage - being an endotherm allows them to live in a wide range of places on Earth & still be active
disadvantage - needs lots of energy, must find food regularly to maintain core temp
small animals have high SA:V ratio & therefore it loses heat quickly - needs to consume more food than its body weight daily
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