Week 5 Flashcards
Chemical reactions in a cell are accelerated by…?
chemical catalysts
What is the rate of a chemical reaction defined as?
the amount of product formed (or reactant consumed) per unit of time
What are catalysts?
substances that increase the rate of chemical reactions without being consumed themselves
Most, but not all, catalysts are…?
proteins called enzymes
exergonic reactions _____ free energy
release
endogonic reactions ____ free energy
require
All chemical reactions require….?
an input of energy to proceed
Define transition state
the brief time in a chemical reaction in which chemical bonds in the reactants are broken and new bonds in the product are formed.
the transition state is highly ____ and therefore has large amounts of…?
unstable
free energy
negative ∆G means the reaction is _____
spontaneous
Define activation energy (EA)
The energy input necessary to reach the transition state.
The lower the energy barrier, the ____ the reaction
faster
Enzymes work by ____ the transition state
stabilizing
Does catalyzing a reaction change the value of ∆G?
No
what is the sign on ∆G for non spontaneous reactions?
positive
The higher the energy barrier, the ____ the reaction
slower
Define substrate
A molecule acted upon by an enzyme.
How does an enzyme speed up the rate of a reaction?
the enzymes forms a complex with the substrate and while the substrate is still part of the complex it is converted into the products. The complex then dissociates to leave you with your final product
Define active site
The portion of the enzyme that binds substrate and converts it to product.
Is the size of an active site big or small compared to the enzyme?
very small
Why are enzymes specific?
- because they recognize either a unique substrate or class of substrates that share common chemical structures, and
- they catalyze only one reaction or a very limited number of reactions
Define activator
A synthesized compound that increases the activity of an enzyme.
Define inhibitor
A synthesized compound that decreases the activity of an enzyme.
______ decrease the activity of enzymes
inhibitors
____ increase the activity of enzymes
activators
What are the two classes of inhibitors?
irreversible and reversible
What is the difference between reversible and irreversible inhibitors?
irreversible inhibitors form covalent bonds with enzymes
reversible inhibitors form weak bonds with enzymes
What are the two ways inhibitors work?
- an inhibitor with a structure similar to a substrate binds to the active site of an enzyme and therefore competes with substrates for active sites
- an inhibitor which is unlike a substrate binds to a site other than the active site and inhibits the activity of the enzyme
define allosteric enzymes
An enzyme whose activity is affected by binding a molecule at a site other than the active site. Typically, allosteric enzymes change their shape on binding an activator or inhibitor.
Define negative feedabck
Describes the effect in which the final product of a biochemical pathway inhibits the first step; the process in which a stimulus acts on a sensor that communicates with an effector, producing a response that opposes the initial stimulus. Negative feedback is used to maintain steady conditions, or homeostasis.
