Lecture 7: enzyme structure and function Flashcards
Enzymes
a class of protein that catalyze specific chemical reactions
chemical reaction
the breaking and making of chemical bonds leading to changes in the composition matter
forms of energy in Biology
potential energy of position
kinetic energy of motion aka cellular work
Potential energy of position
- covalent chemical bonds
- concentration gradients
- electrical charge differences
kinetic energy of motion aka cellular work
- active transport of molecules across a membrane
- chemical reactions that reorganize matter into higher energy states
- mechanical motion of items
Types of cellular work
transport work
mechanical work
chemical work
phosphoanghydride bond
(of ATP) releases energy that powers cellular work
metabolism
the sum total of all chemical reactions occurring in a biological system
anabolic reactions
join simple molecules to form more complex ones, endergonic, require energy to form higher energy products
catabolic reactions
break down complex molecules, exergonic, release stored energy in the reactants
ATP is a…
RNA nucleotide
what is required to initiate an energy releasing chemical reaction, like the combustion of Methane?
energy
energy barrier
(aka activation energy) inhibits exergonic reactions
How do enzymes catalyze reactions?
by lowering the activation energy
What changes the shape of enzymes?
interactions between substrates and enzymes
Which interactions are sensitive to pH, temperature, and force and why?
hydrogen bonding, ionic bonds, and hydrophobic interactions
because they are weak bonds
enzyme active sites have….
specific patterns of shape and charge that bind with the substrate
cofactors
inorganic ions that bind to enzymes and initiate transition state molecule
coenzymes
adds or removes chemical groups from enzymes
prosthetic groups
covalently bond non-amino acids components of enzymes
rate of reaction w/o enzymes
-the reaction rate without enzymes is directly proportional to the concentration of the substrate
rate of reaction w/ an enzyme
once the reaction rate with an enzyme reaches a maximum, the rate is unaffected by increased concentration of the substrate
on a reaction rate graph, where is the rate of the reaction equal to zero?
at the origin
Collision Theory
as the density of the substrate increases, the rate of the reaction increases due to the collisions
graph of rate of reaction / enzyme concentration
directly proportional
point of saturation
the point at which adding more concentration does not affect reaction rate
rate of reaction =
amount of product/time
amount of product/time graph
- the slope of the line is equal to 0 at 0% substrate
- the rate of reaction is about equal at the highest substrate concentrations
enzyme denaturation
after an optimal temperature, when temperate is increased, non covalent bonds break and the activity of the enzyme decreases
irreversible inhibition
- inhibitor covalently binds to side chain in the active site
- the enzyme is permanently inactivated
reversible chemical inhibitors
- noncompetitive
- competitive
competitive inhibitors
- slow the rate of reaction by occupying active sites of enzymes
- competes with natural substrate for active sites
- as substrate concentration increases, the active site becomes saturated with the substrate and the effect of the inhibitor is decreased
noncompetitive inhibitor
- binds at a site distinct from the active site
- this causes allosteric change in the shape of the enzyme that decreases the maximum enzyme function
allosteric regulation
- changes the shape of the enzyme
1. phorsphylation: covalent addition of phosphate group (kinase)
2. non-covalent binding of other molecules at regulatory site
2 classes of enzymes
- kinase- covalently binds phosphate
2. phosphatase- removes phosphate group
