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Biochem Exam 2
| Question | Answer |
|---|---|
| The three ways to increase the rate of a chemical reaction | 1. Increasing temperature 2. Increasing the conc. of the reacting substances 3. Adding a catalyst |
| The 6 major classifications of enzymes | 1. Oxidoreductases 2. Transferases 3. Hydrolases 4. Lyases 5. Isomerases 6. Ligases |
| Type of reaction it catalyzes: Oxidoreductases | Oxidation-Reduction reactions |
| Type of reaction it catalyzes: Transferases | Transfer of functional groups |
| Type of reaction it catalyzes: Hydrolases | Hydrolysis reactions |
| Type of reaction it catalyzes: Lyases | Group eliminations (often to form double bonds) in a reversible reaction and a group may be added |
| Type of reaction it catalyzes: Isomerases | Isomerization within the same molecule |
| Type of reaction it catalyzes: Ligases | Bond formation coupled with the hydrolysis of ATP |
| What is the highest point of the activation energy barrier | Transition state |
| ΔG<0 | Spontaneous, favorable, exergonic |
| ΔG>0 | Non-spontaneous, unfavorable, endergonic |
| Enzyme which requires a cofactor but does not have one bound, catalytically inactive | Apoenzyme |
| Apoenzyme and cofactor, catalytically active | Holoenzyme |
| All facilitate enzymatic reaction | Cofactors |
| Examples are Zn2+, Mg2+ | Metal ions |
| Small organic molecules | Coenzyme |
| Enter and exit the active site | Co-substrate |
| Tightly bound, often by a covalent bond | Prosthetic. group |
| H+ transfer from an acid, lowers the free energy of the transition state | General Acid Catalysis |
| H+ is abstracted by a base to lower the free energy of the transition state | General Base Catalysis |
| Accelerates reactions by forming a covalent bond between enzyme and substrate | Covalent catalysts |
| What is a chymotrypsin | Serine protease |
| Catalytic triad AAs | Asp, His, Ser |
| Catalytic triad functions in serine proteases | Asp 102 anchors His 57, His 57 acts as a general base and later as a general acid, Ser 195 acts as a nucleophile |
| The 4 properties catalytic activity of enzymes depend on | 1. Transition state stabilization 2. Proximity and orientation 3. Induced fit 4. Electrostatic catalysis |
| Inactive precursors of enzymes that are activated by proteolysis | Zymogens |
| Proteolytic Cleavage Preference: C-terminal side of aromatic amino acids Phe, Tyr, Try or any other large hydrophobic side chains such as Leu | Chymotrypsin |
| Proteolytic Cleavage Preference: C-terminal side of basic amino acids (Lys, Arg) | Trypsin |
| Proteolytic Cleavage Preference: C-terminus of small nonpolar amino acids (alanine, valine, glycine) | Elastase |
| Needs to be cleaved for activation | Zymogens |
| Measured as the rate of product formation and varies with the substrate concentration | Enzyme's activity |
| Has a velocity (rate) that does not depend on substrate concentration | Zero order |
| Has a velocity (rate) that is dependent on the concentration of only one substrate | Unimolecular first order |
| Has a velocity (rate) that is dependent on two substrate concentrations | Bimolecular second order |
| The substrate concentration at which the reaction velocity is half-maximal, unique for each enzyme-substrate pair | Km |
| Catalytic rate constant, the number of substrate molecules transformed into product molecules by an enzyme per unit time when the enzyme is saturated with the substrate | Kcat |
| Catalytic efficiency, how avidly the enzyme binds its substrate and how rapidly it converts the substrate to product | Kcat/Km |
| Substances that bind ___ to an enzyme can inhibit its activity | Irreversibly |
| Reversible inhibitor that increases Km w/o affecting Vmax | Competitive inhibitor |
| Reversible inhibitor that decreases Vmax w/o affecting Km | Noncompetitive inhibitor |
| Binds to the active site, most common form, often resembles the substrate | Competitive inhibitor |
| Binds to different sites on the enzyme and not the active site, can bind to either a E or E-S complex | Noncompetitive inhibitor |
| The sum of catabolic and anabolic activities | Metabolism |
| Catabolism of amino acids, monosaccharides, and fatty acids involves ___ | Oxidizing carbon |
| Anabolism of amino acids, monosaccharides, and fatty acids involves ___ | Reducing carbon |
| 6 overviews of metabolism | 1. Monomers are formed 2. Intermediates with 2 or 3 carbons are formed 3. Carbons are fully oxidized to CO2 4. Electron carriers gain electrons 5. Electron carriers are recycled via electron loss 6. ATP and H2O are produced |
| The heat content of a system | Enthalpy (H) |
| A measure of the system's disorder or randomness | Entropy (S) |
| A measure of the free energy of a system based on H and S | Gibbs free energy (G) |
| Glycogen to glucose | Glycogenolysis (Glycogen breakdown) |
| Glucose to the 3-carbon pyruvate | Glycolysis |
| Synthesis of glucose from smaller precursors | Gluconeogenesis |
| Glucose to glycogen | Glycogenesis (Glycogen synthesis) |
| 10 step pathway, Glucose is converted to two molecules of pyruvate, Energy is invested in the first half of the pathway, The second half of the path generates 4 ATP and 2 NADH | Glycolysis |
| Hexokinase Reaction, ATP is invested, ATP hydrolysis drives the reaction, reaction is irreversible | Glycolysis Step 1 |
| Phosphoglucose Isomerase Reaction, Conversion of a glucose-6-phosphate to fructose-6-phosphate (Isomerization rxn), rxn is near equilibrium | Glycolysis Step 2 |
| Phosphofructokinase Reaction, Another ATP is invested, ATP hydrolysis drives the rxn, Irreversible | Glycolysis Step 3 |
| Most potent activator of PFK | Fructose-2,6-bisphosphate |
| Inhibits PFK | Phosphoenolpyruvate |
| Activates/promotes PFK | ADP |
| Aldolase Reaction, Rapid consumption of GAP and DHAP, Aldolase cleavage reaction | Glycolysis Step 4 |
| Triose Phosphate Isomerase Reaction, Converts DHAP to GAP (Isomerization rxn), GAP is quickly consumed in the next rxn, Results in 2 GAPs proceeding through remainder of glycolysis | Glycolysis Step 5 |
| GAP Dehydrogenase Reaction, Phosphate does not come from ATP, NAD+ is reduced to NADH + H+, Rxn is both phosphorylation and oxidation-reduction | Glycolysis Step 6 |
| Phosphoglycerate Kinase Reaction, ATP is formed | Glycolysis Step 7 |
| Phosphoglycerate Mutase Reaction, Phosphate gets moved to C-2 | Glycolysis Step 8 |
| Enolase Reaction, Enolase catalyzes a dehydration reaction, H2O is produced | Glycolysis Step 9 |
| Pyruvate Kinase Reaction, ATP formed, Irreversible reaction | Glycolysis Step 10 |
| 1. Activated by fructose 2,6-bisphosphate, ADP 2. Inhibited by ATP, phosphoenolpyruvate, citrate | Phosphofructokinase |
| Inhibited by high conc of glucose 6-phosphate (product inhibition) | Hexokinase |
| Activated by fructose 1,6-bisphosphate (feed forward regulation) | Pyruvate Kinase |
| The fates of pyruvate | Lactate, Oxaloacetate, Acetyl CoA |
Created by:
tm15