Enzyme Flashcards
globular proteins that catalyse chemical reactions in living organisms
enzyme
specific, increase rate of reaction, unchanged at the end of reaction
properties of enzymes
metabolic reactions must reach this point to form products
activation energy En
build molecules
anabolic reactions
break down molecules
catabolic reactions
lower the amount of activation energy needed, speeding up reactions, not used up or altered
how do enzymes work
releases heat, gibbs free energy is negative
exergonic
requires input of energy, gibbs free energy is positive
endergonic
reactant for a specific enzyme
substrate
interact with the substrate, causing physical stress in order to break bonds and create products, reducing activation energy
amino acid side groups
depression in the surface of the globular protein where substrate binds
active site
original model, goes straight from substrate + enzyme to enzyme substrate complex and enzyme + products
lock and key model
active site is caused by folding, enzyme adjusts its shape to allow substrate to fit exactly into active site
induced fit model
substrate and enzyme interacting, held together by hydrogen bonds and weak ionic interactions
enzyme substrate complex/transition state
minimum amount of energy required to start the reaction
activation energy
reduce the height of the energy barrier, lowering the activation energy required to start the reaction, increasing the rate of reaction
effect of enzyme on reaction
factors that affect enzyme activity
temperature, pH, substrate concentration, enzyme concentration
reaction rate increases as temperature increases within a temperature range towards optimal temperature
temperature
enzyme denatures, loss of enzyme activity
above optimal temperature range
enzyme is inactive
below optimal temperature range
enzymes function best at an optimal pH, usually in the range of pH 6-8
pH
if amount of enzyme is kept constant and substrate concentration is increased, reaction rate increases until it reaches max
substrate concentration
when adding substrate has no effect because all enzymes are part of an enzyme substrate complex
substrate saturation
if amt of substrate is kept constant and enzyme concentration is increased, reaction rate increases until it reaches a maximum
enzyme concentration
when adding amount of enzyme has no effect on reaction rate because all substrate is bound
enzyme saturation
receptor site that is close to but not directly on the active site of the enzyme
allosteric site
shapes of enzymes (active/inactive) that enzymes will oscillate between
conformations
chemicals that bind to specific enzymes and inhibit enzyme activity, important as enzyme activity must be controlled to coordinate cellular activities
enzyme inhibitors
similar in shape to substrate and competes directly with substrate, binds to active site and inhibits enzyme function, can be overcome by increasing concentration of substrate
competitive inhibitor
binds to allosteric site and inhibits enzyme activity by altering enzyme conformation, causing active site to change shape, preventing substrate binding shutting off enzyme activity
allosteric inhibitor
chemicals that bind to active site/allosteric site and turn on/enhance/stimulate enzyme activity, allowing cellular activity coordination
activators
binds to allosteric site of enzyme, altering conformation of the enzyme, causing active site to change shape, stabilizing conformation for the substrate, turning on/enhancing enzyme activity
allosteric activator
substrate is activator and binds to active site, stabilizing conformation of the enzyme, allows additional active sites to bind more easily with substrate, turning on/enhancing enzyme activity
substrate activator
inorganic ions (copper, zinc, iron) located in active site, attracting electrons from substrate, increasing binding ability between enzyme and substrate
cofactors
organic non-protein molecules that are cofactors
coenzymes
more permanent cofactors/coenzymes, bound more tightly, sometimes with a covalent bond to active site
prosthetic groups
method of metabolic control where product formed later in sequence of reactions will allosterically inhibit an enzyme that catalyzes a reaction occurring earlier in the metabolic process
feedback inhibition
