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CHM 140

CH 23

QuestionAnswer
____Only about ½ of the known enzymes contain proteins FALSE
____Some enzymes are so specific that they catalyze only one reaction. TRUE
____The metal portion of an enzyme is called the coenzyme. FALSE
____The lock and key model is a flexible, moving enzyme model. FALSE
____In feedback control, inhibition of an earlier reaction may be competitive or non-competitive TRUE
_____Protein modification can be reversed. TRUE
_____Protein modification can either increase or decrease enzyme activity. TRUE
stereospecific enzyme- enzymes that catalyze the reactions of a particular stereoisome
substrate- the compound or compounds whose reaction an enzyme catalyzes
cofactor- a nonprotein portion of an enzyme that is involved in a chemical reaction; may be metal or organic
coenzyme- an organic cofactor; is not a protein
apoenzyme- the protein part of an enzyme
active site- the specific portion of the enzyme to which a substrate binds during reaction
activation- any process that initiates or increases the activity of an enzyme
inhibition- any process that makes an enzyme less active or inactive
competitive inhibitor- substance that binds to the active site of an enzyme thus preventing binding of substrate
noncompetitive inhibitor- any substance that binds to a portion of the enzyme other than the active site and thus inhibits the activity of the enzyme
enzyme activity- a measure of how much a reaction rate is increased in the presence of an enzyme catalyst from the absence of the enzyme catalyst
Name the six major groups or classification of enzymes a)oxidoreductases, b)transferases, c)hydrolases, d)lyases, e) isomerases, f) ligases
What 4 factors affect enzyme activity? 1)enzyme concentration 2)substrate concentration 3)temperature 4)pH
Describe the difference between the lock and key model and the induced fit model of substrate-enzyme interaction. In lock and key model, enzyme and substrate are rigid 3-D models & substrate fits into active site like a key in a lock.The induced fit model is a flexible enzyme where active site becomes modified to accommodate substrate like a hand being put in a glove
What 5 amino acids are generally found in the active sites of most enzymes? gluatmic acid, aspartic acid, arginine, histidine, and cysteine
What is unique about the 4 of the 5 enzymes? acidic or basic side group
Explain the difference between competitive and non-competitive inhibition with respect to their mechanism of inhibiting substrate binding to the active site. Competivite inhibitor binds to active site of enzyme preventing binding of substrate. Noncompetitive inhibitor binds to portion of enzyme other than active site and inhibits activity of enzyme by changing shape of binding site
Draw in the lines on the following graph demonstating the effect on normal enzyme activity by competitive and non-competitive inhibition.
feedback control- an enzyme-regulation process where the product of a series of enzyme-catalyzed reactions inhibits an earlier reaction in a sequence
proenzyme- an inactive form of an enzyme that must have part of its polypeptide chain cleaved before it becomes active
allosterism- a type of enzyme regulation based on an event occurring on the enzyme at a place other than the active site but that creates a change in the active site
allosteric enzyme- an enzyme regulated by an allosteric effect
negative modulation- inhibition of an allosteric enzyme
positive modulation- stimulation of an allosteric enzyme
regulator- a substance that binds to an allosteric enzyme
isoenzyme- two or more enzymes that differ in primary structure (amino acid sequence) but each catalyzes the same reaction
protein modification- the process of affecting enzyme activity by covalently modifying it
What must be done to a proenzyme to make it active? must have part of its polypeptide chain cleaved before it becomes active
What is the difference between noncompetitive inhibition and allosterism? (Noncompetitive inhibition only ____ enzyme activity while allosterism may ____or ____ enzyme activity.) Decreases, Increases, Decreases
Describe how a regulator works to control enzyme activity. 1. The regulator binds to an allosteric enzyme at a site other than the active site 2. This binding changes the shape of the active site. 3. The regulator may act as an inhibitor (negative modulation) or a stimulator (positive modulation)
Created by: fallsummerspring
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