Dr Quan Exam 1 Study Guide Flashcards
Most critical function of an enzyme
Accelerate reactions by millions fold
Optimum temperature for enzymes
37 degrees C
Optimum pH for enzymes
~7
Pepsin exception: 1.5-2
Composition of complex enzyme
Apoenzyme (protein part) and Cofactor (Prosthetic group or Coenzyme)
Catalyze oxidation-reduction reactions
Oxidoreductase
Catalyzes group transfers
Transferase
Catalyzes hydrolysis rxns where water is acceptor of transferred group
Hydrolase
Catalyze isomerization rxns (D to L, L to D)
Isomerase
Catalyze the lysis of substrate, generating a double bond in a nonhydrolytic, nonoxidative elimination.
Lyases
Catalyze joining of two substrates and requires ATP (energy)
Ligase
Specific region of enzyme where substrate molecule is bound
Active Site
Enzyme active site only able to accept specific substrate type
Lock and Key Theory (Fischer Theory)
Enzyme acts only on one substrate
Absolute Specificity
Enzyme acts on different substrates that have same bond type
Relative Specificity
Enzyme Activity Definition
1 international unit (IU) of enzyme catalyzes conversion of 1 micromol of substrate to product per minute
Km (Michaelis Constant) definition
Substrate concentration @ 1/2 Vmax
Reversible Inhibitors
Can rapidly dissociate
Weak, noncovalent interaction
Irreversible Enzyme Inhibition
Slow dissociation of EI complex
Tightly bound
Competitive Inhibitor
Competes with substrate at active site.
Km increased, Vmax unchanged
Non-competitive inhibitor
Binds to enzyme site different from active site.
Km unchanged, Vmax decreased
Uncompetitive Inhibitors
Binds to ES complex (not free enzyme)
Decreases both Km and Vmax
Positive (stimulating) or Negative (inhibiting) regulation of enzyme. Site different from active site.
Allosteric Regulation
Covalent attachment to modify activity (EX: Phosphorylation)
Reversible Covalent
Multiple forms of an enzyme which differ in structure/genes but catalyze same reaction
Isoenzymes
Enzymes are synthesized as inactive precursors (zymogens) and activated by cleavage. (EX: Insulin)
Proteolytic Activation
Channeling of reactants between active sites
Metabolic Channeling
Gycolysis starts and ends where?
Glucose -> lactate
Glucose generates what five things?
- ATP
- Glycogen
- Ribose
- Lipid molecules
- NADPH
Glycolysis has what two stages?
Investment and yield
Glucose can be trapped in a cell in the form of?
Glc-6-P
Rate limiting enzyme of glycolysis
PFK-1
What two things catalyze the yield of ATP in glycolysis?
PGK and pyruvate kinase
Glycolysis ATP account
Use 2 ATP to generate 4 ATP.
Net gain of 2 ATP
Pyruvate can be transformed to _______ to regenerate ______
Lactate
NAD+
Hexokinase can be inhibited by
Glc-6-P
PFK-1 can be inhibited by _____ and activated by _____
ATP
AMP
Pyruvate Kinase can be activated by ______
Fructose-1,6-BP
Pentose phosphate pathway is important for the generation of _____ and _____
NADPH
Ribose
Structure of glycogen
C24
H42
O21
What is used as the building block for glycogen?
UDP-glucose
What extends the chain of glycogen?
Glycogen synthase
What initiates glycogen synthesis?
Glycogenin
What catalyzes the breakdown of glycogen?
Glycogen Phosphorylase
What can be used to treat diabetes?
Inhibition of glycogen phosphorylase
What enzyme stimulates glycogenolysis?
Glucagon
What two things increase the activity of glycogen phosphorylase?
Epinephrine and glucagon
What is basically the reverse of glycolysis?
Gluconeogenesis
Where does the TCA cycle occur?
Eukaryotic cells -> mitochondrial matrix
Two major functions of TCA cycle:
- Increase cell’s ATP-producing potential by generated reduced electron carriers NADH and ubiquinone
- Provide cell with a variety of metabolic precursors.
What two things are derived from pyruvate?
Acetyl-CoA and Oxaloacetate
What catalyzes the synthesis of acetyl-CoA?
Pyruvate dehydrogenase
The 4 oxidative enzymes in the TCA cycle:
- Isocitrate DH
- AKG DH
- Succinate DH
- Malate DH
Pyruvate DH is negatively regulated by:
- ATP
- Acetyl-CoA
- NADH