enzymes Flashcards
catalyst
substance that can change the rate of a reaction without being altered in the process
enzyme
biological catalyst
Speeds up metabolic reactions by lowering the activation energy
activation energy
energy needed to start reaction
enzyme often ends in
-ase
enzymes are in the form of
proteins
do enzymes affect the change in free energy? how
no
they speed up reactions that would occur eventually
substrate
The reactant that an enzyme acts on
when is an enzyme-substrate complex formed
when The enzyme binds to its substrate
active site
the region on the enzyme where the substrate binds
where does a substrate bind to in an enzymatic reaction
active site
how does the active site lower the activation energy barrier (4 ways)
Orienting substrates correctly
Straining substrate bonds
Providing a favorable microenvironment
Covalently bonding to the substrate
substrate binding process (6 steps)
- substrates enter active site
- substrates held in active site by weak interactions
- active site can lower activation energy and speed up a reaction
- substrates are converted into products
- products are released
- active site is available for two new substrate molecules
induced fit
ENZYME FITS SNUGLY AROUND SUBSTRATE – “CLASPING HANDSHAKE”
an enzyme’s activity can be affected by:
temperature
pH
chemicals
cofactors
non-protein enzyme helpers such as minerals (eg. Zn, Fe, Cu)
coenzymes
organic cofactors (eg. vitamins)
competitive inhibitors
binds to the active site of an enzyme, competes with substrate
noncompetitive inhibitor
binds to another part of an enzyme → enzyme changes shape → active site is nonfunctional
how does a cell regulate metabolic pathways?
switches on/off the genes that encode specific enzymes
allosteric regulation
protein’s function at one site is affected by binding of a regulatory molecule to a separate site (allosteric site)
activator
stabilizes active site
inhibitor
stabilizes inactive form
cooperativity
one substrate triggers shape change in other active sites → increase catalytic activity
FEEDBACK INHIBITION
End product of a metabolic pathway shuts down pathway by binding to the allosteric site of an enzyme
feedback inhibition prevents
wasting chemical resources
feedback inhibition increases
efficiency of cell
where are enzymes in cells?
wherever the most efficient position is. cell is compartmentalized and structures bring order to metabolic pathways. some enzymes are on particular membranes (mitochondria) or in fixed locations in the cell
