Chp. six Flashcards
____ tells if a reaction can thermodynamically happen, but it doesn’t say that it will happen. Rate of reaction is a function of specialized enzymes.
delta G
Molecules that should react with one another often _____ because they lack sufficient energy.
do not
___ is the minimum amount of energy that 2 molecules must have in order to react.
activation energy Ea
For a reaction to occur you must have a ______ and
favorable delta G and enough energy to reach Ea
The rate of enzymatic reaction is proportional to _____ that have an evergy content >=
fraction of molecules
Under most biologically normal conditions, the Ea is ___ that few molecules have that much energy.
so high
The rates of uncatalyzed reaction in cells are ____
very slow.
non-reacting molecules are ____ unstable but ____ stable in a metastable state.
thermodynamically, kinetically
life depends on the high Ea to ____ cellular reactions from happening at appreciable rates ____ in the presence of a suitable catalyst.
prevent, except
Providing a reactive surface is the task of a_____`
catalyst
Protein catalysts are called
enzymes
RNA catalyst are called
ribozymes
3 basic properties of catalysts
- All catalysts increase the rate of a reaction by lowering the Ea requirement.
- All catalysts act by forming transient intermediate complexes with the substrate molecules and thus position them in a manner that facilitates their interaction.
- All catalysts change only the rate at which equilibrium is reached; no effect on the position of the equilibrium.
Every enzyme contains, somewhere within its 3 prime structure, a characteristic cluster of ______ forming an _____.
amino acids, active site
What is the location of domain on the enzyme’s structure where the actual catalytic action occurs
active site
what is usually a groove or pocket with chemical or structuaral properties that accommodate the intended substrate with high specificity
active site
Active site involves only about ____ of the surface area of the enzyme.
5%
Amino acids most commonly found at an active site
cysteine, histidine, serine, aspartate, glutamate, lysine
The amino acids that make up the active site of an enzyme are not usually contiguous along the ___ sequence of a polypeptide. Instead, they are brought into the right conformation by the specific ____ folding of the polypeptide chain and by additional conformational change when the substrate binds.
1 prime, 3-D
The reaction seen in peroxisomes is _____ favorable… yet hydrogen peroxide exists in nature in a _____ state.
thermodynamically, metastable
When ferric ions are added to the solution it increases the reaction rate about
30,000X
fe+3 reacts with O2 to form iron oxides and drive the break down of
H2O2
If ____ is present the reaction occurs about 1x10^9 X faster than if uncatalyzed
catalase
if a catalase is present the reaction occurs about ____ faster than if uncatalyzed.
1x10^9 X
ion groups that are integral parts of enzyme structure
prosthetic groups
Prosthetic groups can be ___ organic molecules or ___ ions or combination of ____
small, metal
Prosthetic groups function as ____ acceptors since none of the a.a. are good _____ acceptors.
electron, electron
