Chapter 8: Energy and Enzymes for Exam 2 Flashcards
The reactant acted on by the enzyme
Substrate
Are prosthetic groups organic or inorganic?
Both
Regulation that can either activate or inhibit activity
Allosteric regulation
Does being spontaneous mean the rxn occurs quickly?
No
How is enzyme function regulated?
Tightly regulated through competitive inhibition and allosteric regulation
What often act as enzyme inhibitors and can have irreversible binding?
Toxins and poisons
What 3 things would enzymes not function without?
Cofactors, coenzymes, and prosthetic groups
How do enzymes catalyze rxns?
By lowering activation energy
What types of drugs inhibit enzymes?
HIV medications, ACE inhibitors (HBP), Prilosec (H+/K+ ATPase), penicillin
What are enzymes?
Proteins or sometimes RNA which act as catalysts and speed up rxns
Factors that affect enzyme activity
Temp and pH
What is induced fit?
When the binding of the substrate causes the enzyme to slightly change shape
How specific do substrates need to be to fit an active site?
Very specific. Only very specific ones can fit the active site
What is the optimal pH for enzymes in humans?
Depends on where they are found
What do enzymes often do?
Catalyze a series of related rxns
Regulatory molecule binds away from the active site and causes change in shape
Allosteric regulation
What does sarin gas do?
Binds to the active site of acetylcholinesterase and acts as a competitive inhibitor that causes ACh to stay in synapse and continue to signal eventually causing death
Six steps of an enzyme catalyzing a rxn
- ) Substrates enter active sites
- ) Substrates are held in active site by weak interactions
- ) Active site can lower activation energy and speed up a rxn
- ) Substrates are converted to products
- ) Products are released
- ) Active site is available for new substrate molecules
Region of the enzyme that actually binds the substrate
Active site
What are coenzymes?
Organic molecules like NAD, B vitamins, CoQ, folic acid that work with enzymes to make them function properly
How does penicillin work?
Blocks the active site of enzyme necessary for cell wall formation in bacteria. Humans don’t need or have that enzyme so it doesn’t effect us
How specific is the rxn catalyzed by a particular enzyme?
Enzymes are very specific
What are prosthetic groups?
Molecules tightly bound to enzymes like retinal (vitamin A), metal ions, and vitamins that work with enzymes to make them function properly
What does feedback inhibition prevent the cell from doing?
Prevents the cell from wasting energy to make excess product
Three things that work with enzymes
Cofactors, coenzymes, and prosthetic groups
Optimal pH for enzymes in stomach?
1-3
Are enzymes consumed in rxns?
No
How are metabolic pathways regulated?
Feedback inhibition
What happens as you inc temp?
Inc rxn rate until a certain temp and then the enzymes will begin to denature
These are usually proteins but can also be RNA
Enzymes
What happens to enzymes at the end of a rxn?
They are not consumed and can catalyze again
How do enzymes work?
They lower the activation energy (Ea)
How does the enzyme shape change during induced fit?
The enzyme shape changes to wrap the substrate
Regulatory molecules resembles the substrate and binds to the active site to block the actual substrate
Competitive inhibition
Examples of prosthetic groups
Retinal (vitamin A), metal ions, and vitamins
Which group is basically part of the enzyme?
Prosthetic groups
What is feedback inhibition?
End product of a pathway can bind to an enzyme that acts earlier in the pathway to inhibit it so it doesn’t waste energy making excess product
Is regulatory binding usually reversible?
yes
Optimal pH for enzymes in blood?
Around 7
What are cofactors?
Inorganic ions like Fe, Zn, Mg that work with enzymes in order to make them function properly
Where is activation energy required in the progress of a rxn
Transition state
What does changing the shape of the enzyme during induced fit do?
Brings chemical groups of active site into optimal position to catalyze rxns
Examples of coenzymes
NAD, B vitamins, CoQ, folic acid
What is activation energy?
Reactants absorb energy from their surroundings to reach state where bonds can change
What is optimal temp for enzymes?
Depends on where the enzyme will function. 98.6F in humans, etc.
When do proteins function best?
Under specific conditions
What does it mean for a rxn to be spontaneous?
It occurs without the need of energy input
Regulatory molecules can leave the enzyme to turn it off and on
Allosteric regulation
How do starting molecules need to change for a rxn to occur?
They usually need to be contorted into an unstable form
Steps in the progress of a rxn?
Reactants to transition state to products
Examples of cofactors
Fe, Zn, Mg
How do enzymes lower activation energy?
Act as a docking site to bring reactants together in proper orientation (bring substrates to correct positioning), stretch reactants toward transition-state form stressing and bending chemical bonds, provide a microenvironment more favorable to a particular rxn, and participate directly in the chemical rxn
