Lecture 9 Flashcards
What are reactants?
The starting molecules of a chemical reaction
What are products?
The final molecules of a chemical recation
What does the free energy charge tell us?
Whether or not a reaction occurred spontaneously or not
What is a living systems free energy?
energy that can do work when temperature and pressure are uniform, as in a living cell
what is delta G
Free-Energy Change
What is an exergonic reaction?
energy released spontaneously
What do enzymes do to metabolic recations?
They speed them up by lowering energy barriers
Thermodynamics does not tell us about the ____ of a reaction.
speed
What is a catalyst?
a chemical agent that speeds up a reaction without being consumed by the reaction
What is an enzyme? Example?
a catalytic protein (occasionally RNA)
What occurs during chemical reactions?
bond breaking and bond forming
What is activation energy (Ea)?
The initial energy needed to start a chemical reaction
What is the activation energy often consist of?
thermal energy that the reactant molecules absorb from their surroundings
What happens at the transition state?
The reactants become unstable and start to go downhill
How is the change in free energy affected by enzymes?
enzymes have no effect on it; they only hasten reactions that would occur eventually
List the 3 characteristics of all enzymes.
-increase speed of reacton by lowering Ea
-Are not altered by reactions
-Can catalyze multiple rounds of reactions
List the 3 characteristics specific to enzymes.
-Highly specific for reactants and reactions they catalyze
-Perform highly specific catalysis (few side products)
-Can be regulated
What is a substrate?
The reactant that an enzyme acts on
What is an enzyme-substrate (ES) complex?
when an enzyme binds to its substrate
The reaction catalyzed by each enzyme is _______.
very specific.
What is the active site?
The region on the enzyme where the substrate binds.
How much enzyme do you need in a reaction and why?
very small amounts because they are used repeatedly (catalytic)
Enzyme shape is not ___ .
static
What are the 4 ways an active site can lower an Ea barrier?
-orienting substrates correctly
-straining substrate bonds
-providing a favorable microenvironment
-covalently bonding to the substrate
What are the three ways an enzymes activity can be affected?
-general environmental factors, such as temperature and pH
-chemicals that specifically influence the enzyme
-substrate concentration
What are cofactors?
Nonprotein enzyme helpers; may be organic or inorganic
What is a coenzyme?
an organic cofactor including vitamins
What is enzyme kinetics?
Measuring the rate if reactions under varying conditions
What can enzyme kinetics tell you?
the catalyst mechanism, its role in metabolism, how its activity is controlled, how a drug might alter it
What is V_max in enzyme kinetics?
-saturation point for a particular amount of enzyme
-maximal reaction rate when substrate is not limiting
What is K_m in enzyme kinetics?
-substrate concentration at which reaction velocity is half maximal
-inversely related to enzyme affinity
What do competitive inhibitors do?
bind the active site of an enzyme, competing with the substrate
What so non-competitive inhibitors do?
bind to another part of the enzyme, making the active site less effective
List some examples of inhibitors?
Toxins, poisons, pesticides, and antibiotics
