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5. ENZYMES AND METABOLISM - Coggle Diagram
5. ENZYMES AND METABOLISM
ENZYMES AS BIOLOGICAL CATALYSTS
ENZYMES ARE GLOBULAR PROTEINS THAT ACT AS BIOLOGICAL CATALYSTS TO INCREASE THE RATE OF CHEMICAL REACTIONS
WITHOUT THEM, DNA REPLICATION WOULD BE UNABLE TO OCCUR WITHIN THE LIFETIME OF A CELL, FOOD WOULD BE UNABLE TO BE CHEMICALLY DIGESTED AND CELL RESPIRATION WULD BE EXTREMELY LOW
ENZYMES CAN BE REUSED BY BINDING WITH THE SUBSTRATE IN THE ACTIVE SITE
THE ACTIVE SITE IS COMPOSED OF A FEW AMINO ACIDS WITHIN THE OVERALL 3D STRUCTURE OF THE ENZYME THAT ENSURE THAT THE ACTIVE SITE HAS THE NECESSARY PROPERTIES FOR CATALYSIS
INDUCED FIT MODEL
THE ENZYME'S ACTIVE SITE IS NOT COMPLETELY TIGID FOR THE SUBSTRATE
THE ACTIVE SITE UNDERGOES A CONFORMATIONAL CHANGE WHEN EXPOSED TO A SUBSTRATE TO IMPROVE BINDING
THE CONFORMATIONAL CHANGE STRESSES BONDS IN THE SUBSTRATE, INCREASING REACTIVITY
MOVEMENT IS NEEDED FOR A SUBSTRATE AND AN ACTIVE SITE TO COME TOGETHER
SOMETIMES LARGE SUBSTRATES ARE IMMOBILIZED WHILE SOMETIMES ENZYMES ARE IMMOBILIZED BY BEING EMBEDDED IN MEMBRANES
RELATIONSHIPS
THE CHEMICAL PROPERTIES OF THE ACTIVE SITE ARE DEPENDENT ON THE 3D SHAPE OF THE ENZYME
ENZYME STRUCTURE CAN BE MODIFIED BY EXTERNAL FACTORS SUCH AS PH OR TEMPERATURE
THESE FACTORS DISRUPT THE CHEMICAL BONDS WHICH ARE NECESSARY TO MAINTAIN THE CHEMICAL PROPERTIES OF THE ENZYME
THE CHANGE OF THE ACTIVE SITE IS CALLED DENATURATION WHICH WILL NEGATIVELY AFFECT THE ENZYME'S CAPACITY TO BIND TO THE SUBSTRATE
ACTIVAITON ENERGY
CHEMICAL REACTIONS REQUIRE ENERGY TO PROCEED, KNOWN AS ACTIVATION ENERGY
ENZYMES LOWER THE ACTIVATION ENERGY TO SPEED THE RATE OF THE REACTION
METABOLIC REACTIONS
METABOLISM DESCRIBES THE NETWORK OF INTERDEPENDENT AND INTERACTING ENZYME-CATALYSED REACTIONS THAT OCCUR WITHIN A CELL
A SERIES OF ENZYME CATALYSED REACTIONS IS A METABOLIC PATHWAY
BECAUSE OF ENZYME SPECIFICITY, MANY DIFFERENT ENZYMES ARE REQUIRED BY LIVING ORGANISMS AND CONTROL OVER METABOLISM CAN BE EXERTED THROUGH THESE ENZYMES
ANABOLIC REACTIONS
BUILD OF COMPLEX MOLECULES FROM SIMPLER ONES
CONDENSATION REACTIONS
EXAMPLE - FORMATION OF MACROMOLECULES FROM MONOMERS BY CONDENSATION REACTIONS
PROTEIN SYNTHESIS
GLYCOGEN FORMATION
PHOTOSYNTHESIS
CATABOLIC REACTIONS
BREAK DOWN COMPLEX MOLECULES INTO SIMPLER ONES
HYDROLYSIS REACTIONS
EXAMPLE - HYDROLYSIS OF MACROMOLECULES INTO MONOMERS IN DIGESTION AND OXIDATION OF SUBSTRATES IN RESPIRATION
INTRACELLULAR
REACTIONS THAT OCCUR AND FUNCTION WITHIN THE CELL
EXAMPLE - GLYCOLYSIS AND THE KREBS CYCLE
EXTRACELLULAR
REACTIONS THAT OCCUR INSIDE THE CELL BUT PRODUCTS LEAVE THE CELL
EXAMPLE - CHEMICAL DIGESTION
HEAT GENERATION IN REACTIONS IS INEVITABLE BECAUSE ENERGY TRANSFERS ARE NOT 100% EFFICIENT
MAMMALS DEPEND ON THIS HEAT PRODUCTION TO MAINTAIN THEIR CONSTANT BODY TEMPERATURE
CYCLICAL PATHWAYS
USE AND REGENERATE A SEQUENCE OF INTERMEDIATES
EXAMPLE - KREBS AND CALCIN CYCLE
LINEAR PATHWAYS
CHAINS OF REACTIONS THAT CONVERT AN INITIAL SUBSTRATE INTO AN END PRODUCT
EXAMPLE - GLYCOLYSIS
FACTORS AFFECTING PATHWAYS ACTIVITIES
VARIOUS EXTERNAL FACTORS MAY AFFECT THE ACTIVITY OF ENZYMES BY EITHER AFFECTING THE FREQUENCY OF ENZYME-SUBSTRATE COLLISIONS OR BY AFFECTING THE CAPACITY OF ENZYMES AND SUBSTRATE TO INTERACT
TEMPERATURE
LOW TEMPERATURE RESULTS IN INSUFFICIENT ENERGY FOR THE REACTION TO PROCEED
INCREASING THE TEMPERATURE WILL INCREASE THE SPEED AND MOTION OF BOTH ENZYME AND SUBSTRATE
THIS IS BECAUSE HIGHER KINETIC ENERGY WILL RESULT IN MORE FREQUENT COLLISIONS
HIGHER TEMPERATURE CAUSES THE ENZYME TO LOSE ITS SHAPE, RESULTING IN THE LOSS OF ACTIVITY (DENATURATION) AS HYDROGEN BONDS ARE BROKEN
PH
CHANGING THE CHARGE OF THE ACTIVE SITE WILL DIMINISH ITS ABILITY TO BIND THE SUBSTRATE
ENZYMES HAVE AN OPTIMAL PH AND MOVING OUTSIDE THIS RANGE DIMINISHES ENZYME ACTIVITY
SUBSTRATE CONCENTRATION
THIS AFFECTS THE NUMBER OF SUBSTRATE-ACTIVE SITE COLLISIONS PER UNIT TIME
MORE SUBSTRATES MEAN THERE IS AN INCREASED CHANCE OF ENZYME AND SUBSTRATE COLLIDING AND REACTING
AT A CERTAIN POINT, THE RATE OF ACTIVITY WILL CEASE TO RISE SINCE THE ENVIRONMENT IS GOING TO BE SATURATED WITH SUBSTRATE AND ALL ENZYMES ARE REACTING
RATE OF REACTION
RATE OF REACTION = 1/ TIME TAKEN (S)
ENZYME INHIBITION AND REGULATION
NON-COMPETITIVE INHIBITION
INHIBITORS ARE CHEMICAL SUBSTANCES THAT CAN BIND TO AN ENZYME AND REDUCES OR STOPS ITS ACTIVITY
NON-COMPETITIVE INHIBITION INVOLVES A MOLECULE BINDING TO A SITE OTHER THAN THE ACTIVE SITE (ALLOSTERIC SITE)
THIS ACTION IS REVERSIBLE
THE BINDING OF THE INHIBITOR TO THE ALLOSTERIC SITE CAUSES A CONFORMATIONAL CHANGE TO THE ENZYME'S ACTIVE SITE
AS A RESULT, THE ACTIVE SITE AND SUBSTRATE NO LONGER SHARE SPECIFICITY
AS THE INHIBITORS IS NOT IN COMPETITION WITH THE SUBSTRATE, INCREASING SUBSTRATE LEVELS WILL NOT DECREASE THE INHIBITOR'S EFFECT
COMPETITIVE INHIBITION
INVOLVES A MOLECULES THAT BINDS TO THE ACTIVE SITE OF THE ENZYME
THE INHIBITOR IS STRUCTURALLY AND CHEMICALLY SIMILAR TO THE SUBSTRATE AND BLOCKS THE ACTIVE SITE
ITS EFFECT CAN BE REDUCED BY INCREASING SUBSTRATE CONCENTRATION
EXAMPLE - STATINS ARE CHOLESTEROL LOWERING DRUGS THAT FUNCTION AS COMPETITIVE INHIBITORS
STATINS BIND TO THE ENZYME USED FOR THE SYNTHESIS OF CHOLESTEROL, AS A CONSEQUENCE CHOLESTEROL LEVELS DECREASE IN THE BLOOD
END-PRODUCT INHIBITION
A FORM OF NEGATIVE FEEDBACK BY WHICH METABOLIC PATHWAYS CAN BE CONTROLLED
THE FINAL PRODUCT IN A SERIES OF REACTIONS INHIBITS AN ENZYME FROM AN EARLIER STEP IN THE SEQUENCE
THE PRODUCT ACTS AS A NON-COMPETITIVE INHIBITION
THIS PREVENTS THE FORMATION OF FURTHER ENZYME-SUBSTRATE COMPLEXES
IT FUNCTIONS TO ENSURE LEVELS OF A PRODUCT ARE REGULATED
EXAMPLE - ISOLEUCINE IS AN AMINO ACID THAT CAN BIND TO THE ALLOSTERIC SITE OF THREONINE DEAMINASE
AS ISOLEUCINE IS USED BY CELLS, ITS CONCENTRATION DECREASES WHICH DECREASES THE NUMBER OF ALLOSTERIC SITES OCCUPIED
MECHANISM BASED INHIBITION
OCCURS WHEN AN ENZYME BINDS TO A COMPETITIVE INHIBITOR AND FORMS AN IRREVERSIBLE COMPLEX WITH IT
THE ONLY WAY TO RESTORE ENZYME ACTIVITY IS TO SYNTHESIZE NEW ENZYMES
EXAMPLE - PENICILLIN WHICH IS AN ANTIBIOTIC
BACTERIAL CELL WALLS ARE COMPOSED OF PEPTIDOGLYCANS HELD TOGETHER BY CROSS-LINKS
WHEN THE BACTERIA IS GROWING, NEW CROSS LINKS ARE FORMED BUT PENICILLIN STOPS THESE TO FORM BY INHIBITING THE ENZYMES THAT CATALYSE THEIR FORMATION
THE ENZYME IS DD-TRANSPEPTIDASE WHICH WILL BIND TO PENICILLIN AND MODIFY IT TO FORM A STBALE ENZYME-PENICILLIN COMPLEX