Chapter 4: 4.3 Enzymes Flashcards
State:
Function of enzymes
Drastically increases rates of reactions, allowing cellular function (and more specifically, metabolism) to occur
Enzymes are highly specific in their ———- (even showing ——————)
- Substrates
- Stereo-specificity
How do enzymes increase reaction rate?
Stabilization of the transition state (lowering the energy)
True or False:
Each enzyme has a specific substrate and active site
True
How many classes of enzymes are there?
6
List:
The 6 classes of enzymes
- Oxidoreductases
- Transferases
- Hydrolases
- Lyases
- Isomerases
- Ligases
State:
Function of oxidoreductases
Catalyzes oxidation-reduction reactions
What are names of oxidoreductases?
Oxidases, dehydrogenases, reductases
What happens in an oxidation-reduction reaction?
- One substrate is oxidized (loses electrons)
- One substrate is reduced (gains electrons)
In redox reactions:
What is the method to keep track of where electrons are going?
Follow the hydrogen atoms, typically:
* Oxidized molecules lose hydrogen atoms
* Reduced molecules gain hydrogen atoms
State:
Function of transferases
Group transfer reactions
- What are kinases?
- What is the process that they perform called?
- Transfer phosphate groups
- Phosphorylation
State:
Function of hydrolases
Catalyzes hydrolysis reactions
What is a hydrolysis reaction?
Breaking apart molecules with water
True or False:
Hydrolases are the largest group of enzymes
True
What enzymes are included in the hydrolase group? (4)
- Proteases
- Lipases
- Nucleases
- Esterases
State:
Function of lyases
Addition of groups to double bonds or removal of groups to form double bonds
What are lyases also referred to as?
Synthases (perform addition reactions)
Give a WIZEPREP example of a(n):
- Oxidoreductase
- Transferase
- Hydrolase
- Lyase
- Isomerase
- Ligase
- Xanthine dehydrogenase
- Transketolase
- Phloretin hydrolase
- Methylisocitrate lyase
- Isopentenyl pyrophosphate isomerase
- Synthetase
State:
Function of isomerases
Transfer groups within molecules (create isomers)
What enzyme type is found in the isomerase group?
Mutases
State:
Function of ligases
Joins two molecules through the use of ATP (energy source)
Define:
Enzyme Active Site
A pocket on the enzyme that provides a specific environment, within which a reaction can occur more rapidly
List:
Levels of specificity of an enzyme active site
- High degree of specificity
- Function group specificity
- Broader specificity
Explain:
High degree of specificity (Enzyme active site)
Only acts properly on only one substrate
Explain:
Functional group specificity (Enzyme active site)
Acts on multiple substrates with a key functional group
Explain:
Broader specificity (Enzyme active site)
Acts on substrates with the same molecular “scaffold”
What is the “lock and key” in an enzyme?
- Lock: Shape of active site
- Key: Substrate
The shape of the active site is complementary to the substrate
True or False:
The enzyme cannot change shape to accept a substrate
False, it is its own microenvironment and can change to accept a substrate
Define:
Nucleophiles
Electron rich species that have an affinity for positively charged (nucleus)
Define:
Electrophiles
Electron poor species that have an affinity for electron rich atoms
Describe:
Nucleophilic substitution
- Electron-rich chemical species (nucleophile) replaces functional group
- The nucleophile replaces an electrophile and leaving the functional group (known as the substrate)
Define:
Proximity Effect
Brings components close together, increasing the chance of completing the reaction
Transition states are ——— and ——–
- Fleeting
- Unstable
How is stabilization of transition state achieved?
The enzyme binds to the transition state and stabilizes it
Describe:
Acid-Base Catalysis
Electrons are either transferred from an acid catalyst to the substrate or from the substrate to a base catalyst
State the role of the functional group for:
Aspartate
Cation binding; proton transfer
State the role of the functional group for:
Glutamate
Cation binding; proton transfer
State the role of the functional group for:
Histidine
Proton transfer
State the role of the functional group for:
Cysteine
Covalent binding of acyl groups
State the role of the functional group for:
Tyrosine
H-bonding to ligands
State the role of the functional group for:
Lysine
Anion binding; proton transfer
State the role of the functional group for:
Arginine
Anion binding
State the role of the functional group for:
Serine
Covalent binding of acyl groups
What can cofactors be?
- Essential Ions
- Coenzymes
For essential ion cofactors:
What are essential ions?
Mg2+, Ca2+, Fe2+, Co+
For essential ion cofactors:
What are the two types?
- Activator ions: Closely bound
- Metal ions: Tightly bound
For coenzyme cofactors:
What are coenzymes?
Organic compounds
For coenzyme cofactors:
What are the two types?
- Cosubstrates: Loosely bound
- Prosthetic groups: Tightly bound
What is NAD+?
Nicotinamide Adenine Dinucleotide
* Coenzyme
* Reduced form is NADH
What is NADP+?
Nicotinamide Adenine Dinucleotide Phosphate
* Coenzyme
* Reduced form is NADPH
What is FAD2+?
Flavin Adenine Dinucleotide
* Coenzyme
* Reduced form is FADH2
What is ATP?
Adenosine triphosphate
* Coenzyme
List:
Forms of Enzyme Regulation
- Substrate Availability
- Covalent Modifications
- Allosteric Control
- Zymogens, Proenzymes
How does Substrate Availability regulates enzymes?
Enzyme can only catalyze reaction if there is substrate present to act on
How do Covalent Modifications regulate enzymes?
Enzyme induced chemical changes to enzymes that can activate or de-activate enzymes
How does Allosteric Control regulate enzymes?
A regulatory molecule binds to a site on the enzyme, separate form the active site, and alters enzyme shape and function
* Feedback inhibition
What are Zymogens and Proenzymes?
Inactive precursors of enzymes
Give an example of zymogens/proenzymes
Digestive enzymes (activate when expelled from cell)
* Trypsinogen to trypsin
* Proelastase to elastase
* Chymotrypsinogen to Chymotrypsin
* Etc.
