Biochem - Enzymes Flashcards
(39 cards)
6 major classes of enzymes:
- Ligases
- Lyases
- Hydrolyases
- Isomerases
- Oxidoreductase
- Transferases
What 4 things affect enzyme reactions?
- enzyme
- substrate
- effectors
- temperature
Do enzymes get used up?
No; they are catalysts
4 reasons biocatalysts are preferred over inorganic catalysts:
- greater reaction specificity: avoid side products
- higher reaction rates: biologically useful timeframes
- milder reaction conditions: conducive to cell conditions
- capacity for regulation: control biological pathways
What 2 reaction conditions are compatible with life?
- 37 degrees C
- pH of 7
Ligases (synthetases)
- join 2 molecules at the expense of ATP
- require energy
Lyases
remove atoms to form double bonds or add atoms to double bonds
Hydrolyases
cleave bonds with addition of water
Isomerases
- move functional groups within a molecule
- only one substrate and one product
- think racemic mixtures or epimers
Oxidoreductases (dehydrogenases)
catalyze oxidation-reduction reactions
Transferases (kinases)
- move functional groups between molecules
- induces kinases
Exergonic
- neg (-) delta G
- spontaneous
- favorable
Endergonic
- pos (+) delta G
- non spontaneous
- nonfavorable
- must be coupled to exergonics in order to form a net delta G that is favorable
H:
- amount of heat absorbed or released
- aka exothermic or endothermic
Exothermic
releases heat -> -
Endothermic
absorbs heat -> +
S:
- entropy
- state of disorder and randomness
What info does delta G provide?
- only spontaneity
- NOT reaction rate
Do enzymes alter delta G?
No
Do catalysts alter reaction equilibria?
No
What do enzymes affect?
they decrease the free activation energy (delta G) of a reaction
Which model goes through a conformational change? (Lock-and-key OR Induced-fit)
Induced-fit
What kinase is in all tissues?
hexokinase
Which model does hexokinase go through?(Lock-and-key OR Induced-fit)
Induced-fit
