Chapter 6: Basic Concepts of Enzyme action Flashcards
Enzymes are …….
- proteins with catalytic properties
- Accelerate the rate of a reaction
- decrease activation energy
- not degraded or destroyed
- highly specific for substrates
Carbonic anhydrase
catalyzes the reaction of adding H2O to CO2
+ fastest known enzymes
Proteolytic enzymes
- catalyze the hydrolysis of peptide bonds
- perform proteolysis -> hydrolysis of peptide bond
- also termed proteases
Proteolytic enzymes’ activity can be specific - T or F
True
Trypsin
- cleavage of a peptide bond on the carboxylic acid of a Lys or Arg.
- specific
+ digestive enzyme
Thrombin
- Cleaves only Arg - Gly bond
+ enzyme found in blood clotting process
+ more specific than trypsin
Papain
- Non-specific cleavage at any peptide bond
+ found in papaya
+ indiscriminate
Oxidoreductase
catalyze oxidation-reduction rxns
(transfer of electrons b/w molecules)
Transferase
- move functional groups Between molecules
Hydrolase
- cleave bonds with the addition of water
-e.g. trypsin
Lyase
- remove atoms to from double bonds or ass atoms to double bonds
+e.g. fumerase -> aerobic fuel metabolism
Isomerase
- move functional groups within a molecule
Ligase
- join 2 molecules at the expense of ATP
-e.g. DNA ligase
4 ways enzymes are named
- naming based on substrate
- naming based on reactions
- having common names (trypsin)
- systematic naming by enzyme commission
Coenzymes
- cofactor
- organic compounds derived from vitamins
- tightly bound are called prosthetic groups
- can also be loosely bound
- e.g. ascorbate (VIT C)
Metals that act as cofactors ….
- Mg (hexokinase)
- Zn (carbonic anhydrase
Apoenzyme
enzyme with no cofactor present
Holoenzyme
(complete) catalytically active enzyme
Describe conditions for different ∆G values
Negative:
- rxn is spontaneous (favored)
- releases E
- Exergonic
Positive:
- non-spontaneous rxn (not favored)
- E input required
- Endergonic
@ Equilibrium:
- no net change in concentration of products and reactants
Reaction Pathway matters for ∆G. T or F
False
- it does not matter
- multistep or single step pathways are possible
∆G° vs ∆G°’
∆G° = standard free energy change
- Standard conditions:
- products/reactants all at 1M
- 298 K (25 C°)
- Pressure at 1 atmosphere
∆G°’ = standard free energy change at pH 7
- For biochemistry
∆G°’ of the hydrolysis of ATP
∆G° = -30.5 kJ/mol
= -7.3 Kcal/mole
- Exergonic reaction
Enzymes alter reaction equilibrium. T or F
- enzymes do not alter equilibrium
- They alter (speed up) the reaction rate
- equilibrium determined ONLY by the free energy difference
Transition State
- molecule is no longer a substrate but not yet the product
- formed during an ezyme/substrate complex
