enzymes Flashcards
biological catalyst that functions to speed up the rate of a biological reaction, but is not altered or consumed in the reaction
enzyme
energy needed for the reaction to go to completion
activation energy
the substances upon which an enzyme acts
substrates
the substances produced by chemical modification of substrates
products
the specific region on/in an enzyme where substrates bind and where the catalytic reaction occurs
active site
the unstable “energized” intermediate formed in an enzymatic reaction that has properties of both the substrate and the product
transition state
three things enzymes do to lower the activation energy
orienting/holding substrates very close together
creating/stabilizing the transition state intermediate
facilitating the reaction via reactive amino acids in the active site
the model that suggests the enzyme active site perfectly matches the shape of the substrate and so the enzyme allows only one substrate to bind to the active site
lock and key model
model that suggests substrates fit to active site like a flexible hand in glove, the enzyme-substrate binding changes the shape of both the enzyme and the substrate to fit snugly
induced fit model
catalyze oxidation-reduction reactions; add/remove electrons from its substrate
oxidoreductases
transfer a functional group from one molecule to another
transferases
cleave bonds by adding a water molecule
hydrolases
remove functional groups via non-hydrolytic reactions
lyases
catalyze rearrangements of functional groups within a molecule
isomerases
use the energy from ATP hydrolysis to form bonds between two substrate molecules
ligases
EC 1-6
- oxidoreductases
- transferases
- hydrolases
- lysases
- isomerases
- ligases
loosely bound non-protein components of enzymes that assist in catalytic reactions
cofactor
two main types of cofactor
organic and inoganic
tightly bound non-protein components of proteins
prosthetic groups
hydrolyzes cellulose, used as a digestive aid and in biofuel production
cellulase
hydrolyzes collagen, promotes burn and would healing
collagenase
hydrolyzes sucrose, used in the manufacture of soft-centered candy
intertase
hydrolyzes lipids, used as a digestive aid and improves the flavor of cheese
lipase
hydrolyzes pectin and clarifies fruit juice
pectinase
hydrolyzes protein and used in detergents
protease
the maximum possible velocity that a reaction can have at infinite substrate concentration
V max
the half maximal velocity of a reaction
1/2 V max
the substrate concentration at which the enzyme has half maximal velocity
Km
which velocities are the most relevant
the initial velocities
reaction velocities ____ with time
slow down
three reasons why enzymes rarely operate at true V max
substrate in most cells is not high enough
little or no regulation by substrate at V max
substrate at Km is more realistic
an indication of enzyme affinity for substrate
Km
enzymes with ____ have greater substrate affinity
lower Km’s
what are the axis for the lineweaver-burk equation graph
x axis: 1/substrate conc.
y axis: 1/v
the amount of enzyme that produces one mole of product per minute
enzyme unit
amount of enzyme that produces one mole of product per second
katal
micromoles of product formed per minute per mg protein
specific activity
the number of substrate molecules converted to product per unit time by a single molecule of enzyme
turnover number (Vmax/[Enz])
an estimate of how perfect the enzyme is or how well the enzyme performs when S is low
catalytic efficiency (Kcat/Km)
