Chapter 12 (12.6 - 12.7) Flashcards
Enzymes
- known as GLOBULAR PROTEINS
- help SPEED UP biochemical reactions
- can be REUSED
- often end in “ASE”
- goes from SUBSTRATES —-(E)—–> PRODUCTS
absolute specificity
the enzyme only accepts ONE specific substrate
relative specificity
the enzyme can accept a RANGE of substrates (depending if it has the same functional group or similar structures)
ex. oxidation
aldehyde reductase
- an example of RELATIVE SPECIFICITY
- this CATALYZES THE REDUCTION OF AN ALDEHYDE
(opposite of oxidation)
where do substrates bind to?
- the ACTIVE SITE
1) creation of an enzyme-substrate complex formation
2) reaction starts
3) product leaves/enzyme stays in ORIGINAL FORM (repeats cycle!)
cofactors
some enzymes need COFACTORS to function
1) inorganic ions/metallic ions
2) organic compounds aka COENZYMES - comes from VITAMINS
pH optimum
the pH where enzymes are MOST ACTIVE
*typical around 7 (except pepsin - 1.5)
temperature + catalytic activity?
catalytic activity will INCREASE with temperature until the protein DENATURES
temperature optimum
the temp. where enzymes are most ACTIVE
*around 37 degrees Celsius
Michaelis-Menten enzymes
- can be describe in a 2-step process
- characterized by two parameters:
- Michaelis constant
- Vmax
Michaelis constant
the AFFINITY (the tendency to bind) between an enzyme and its substrate
Vmax
the maximum velocity or reaction rate
inhibitor
reduces an enzyme’s activity
irreversible inhibitors
react COVALENTLY with an enzyme
*aspirin - reduce inflam.
reversible inhibitors
binds to the enzyme and INTERFERES with the activity
- binding is TEMPORARY
- the inhibitory effect is TEMPORARY
competitive inhibitors
- type of REVERSIBLE INHIBITOR
(compete for that binding active site)
(substrate similar structure) - AFFECTS AFFINITY or KM
noncompetitive inhibitors
- binds to site in enzyme DIFFERENT than the active site
- binding affects the RATE or VMAX
allosteric enzymes
- have MORE THAN ONE POLYPEPTIDE CHAIN
- COOPERATIVE BEHAVIOR:
binding of substrate to active site effects other substrates and their bindings
allosteric enzymes are affected by?
allosteric effectors: change the SHAPE of enzyme and active site
positive effectors
ENHANCES binding of substrate and INCREASES RATE OF REACTION
negative effectors
REDUCES binding of substrate and SLOWS RATE OF REACTION
- helps prevent its own overproduction - called FEEDBACK INHIBITION
covalent modification + zymogens/inactive enzyme precursors
another way allosteric enzymes are controlled
(2 ATP - 2 ADP - covalent mod.)
(“gen” - zymogen)
