Enzymes Flashcards
What are the key structural features of enzymes?
Tertiary structure, single polypeptide, 2+ polypeptides held together, additional components.
Define metabolism.
The sum of all the chemical reactions in a living organism
What factors affect enzyme activity?
Type of enzyme
Temp
PH
Substrate conc
Enzyme conc
Presence of cofactors
Inh8ibitos
How does substrate conc affect enzyme activity?
Reaction rate depends on this. Most efficient when excess of substrate present as rapid successful collisions
How does enzyme conc affect enzyme activity?
Increases, initial rate increases until substrate becomes limiting.
Define enzyme kinetics.
Study of the rate at which an enzyme works.
Depends on the type of enzyme, temp, concs, pH, cofactors or inhibitors.
How is enzyme catalysis modelled?
E + S <=> EZ -> E + P
What are the assumptions of Michaelis and Menten?
Product production = linear with time
[S] far exceeds [E] and is constant
Single enzyme forms product
There is negligible spontaneous creation of product w/o enzyme
The conditions are optimal
What is the rate of reaction (v)?
The number of substrate molecules converted to product per unit time.
What is the Michaelis-Menton equation?
Describes how rate of reaction OR velocity varies with substrate conc.
The constant is Km.
What is the Michaelis-Menton constant (Km)?
Value that numerically describes [S] at which half the enzymes active sites are occupied by substrate.
Determines the affinity of the substrate for the enzyme and the rate at which substrate bound to enzyme is converted to product.
How is Km interpreted?
Numerically low = only small amount of substrate needed to saturate. High affinity for substrate.
Numerically high = high substrate conc needed to saturate enzyme. Low affinity for substrate.
What is the Vmax?
The max velocity of the reaction or infinite substrate conc is when the rate does not increase past a point bc there is enough substrate to saturate all AS.
How are Vmax and Km related?
At low levels of [S], initial V increases linearly with increasing [S]
As [S] increases, gains in velocity plateaus
The [S] that produces V is 1/2 of Vmax
What is a Lineweaver-Burk plot?
When v0 is plotted against [S], not always possible to determine when Vmax achieved.
- X intercept used to determine Km.
- y intercept determine Vmax
- slope = ratio of Km to Vmax.
