Biology: enzyme structure and function, factors that affect reaction rate, activation energy
Metabolism
Web of all enzyme-catalyzed reactions in a cell or organism
Anabolism
Synthesis of complex molecules from simpler molecules. This includes formation of macromolecules from monomers by condensation reaction
Catabolism
Breakdown of complex molecules into simpler molecules. This includes breakdown of macromolecules into monomers by hydrolysis reaction
Condensation reaction
Chemical reactions in which reactants are joined together to form a product with water
Hydrolysis reaction
Chemical reactions in which reactants are separated using water to form product
Endothermic Reaction
A reaction that absorbs energy in the form of heat
Exothermic Reaction
A reaction that releases energy in the form of heat
Collision Theory
Reactants (including enzymes and substrates) collide
with the correct orientation (i.e., in the "right" place)
with enough energy (E ≥ Ea)
Kinetic Energy
All matter is made of particles, all particles are in constant motion, the motion is random but linear, collisions are elastic
Enzyme
An enzyme is a biological (protein) catalyst.
● A catalyst increases reaction rate but is not used up (it is recycled).
● An enzyme is biological which means that it is found in living things. It is a protein.
Enzyme Specificty
An enzyme binds to and reacts with specific substrates according to the lock-n-key model. This explains substrate-enzyme specificity. The enzyme is the lock. The active site is the keyhole where the reaction takes place in the enzyme. The substrate must fit the active site - the shape of the substrate is complementary to the shape of the active site. The substrate is the key that fits into the active site which is the keyhole. The substrate is the reactant.
Enzyme Catalaysis
An enzyme increases reaction rate but is not permanently changed in the reaction
● An enzyme reacts with a substrate through an alternate reaction pathway
● The activation energy of alternate reaction pathway is less than that of the reaction pathway
without the enzyme
Reaction Rate
Change in a quantity over time, in terms of reactants, it is the rate at which they disappear. This is a negative change. In terms of products, it is the rate at which they appear. This is a positive change.
Reaction Rate Equation
The equation is change in amount ÷ change in time. Amount may be volume (of a gas), mass, temperature (change is a consequence of the reaction), height, length and so forth.
Reaction Rate Graph
Average rate is the change in amount / time (the slope) Instantaneous rate is the slope of a tangent at a given point
Example Reactants Analysis
As the reaction progresses, the concentration of reactants decreases. This leads to lower frequency of collision with the correct orientation and sufficient energy. Thus, rate decreases as reactions progress - highest at the beginning and lowest at the end.
Factors affecting Reaction Rate
Temperature, concentration, surface area and PH