Chapter 19 Flashcards
Turnover number
Number of reactions per second
> speed of enzymology reactions measured by this
> most catalyze 100-1000 per sec
Enzymes
> biological catalyst. -proteins
- make reactions happen faster
- chiral
- highly specific(catalyze only one type of reaction)
- produces one product, w/no side reactions
Enzymes as proteins
water soluble: globular proteins Insoluble :fibrous ex: RNA >specific shape >flexible >Denaturation >side chain interactions
Active site
Fold or grove on enzymes surface where chemical reactions happen.
Substrates
Reactant molecules
Cofactors
Non-protein part of an enzyme that is essential to enzymes catalytic activity.
>metal ion
>coenzyme
•vitamins provide coenzyme cofactors
Function of coenzymes
Coenzymes are bound to active site, participate in chemical reaction
>cofactors and coenzymes provide a charge or functional groups needed for reaction to occur
Enzymes: regulated
Regulation allows cells to respond to changes
•Activity is carefully regulated:
>turned on and off
>reaction occurs by interaction w/specific molecules
Naming enzymes
- ase” newer names( 2parts)
1) substrate 2) type of reaction
-in” older names (1 part)
Function or name
Oxidase
Catalyze an oxidation
Dehydrogenase
Removes 2 hydrogen atoms
Transaminase
Transfers amino group
Kinase
Transfers phosphate group
Lipase
Hydrolysis of lipids
Protease
Hydrolysis of proteins
Phosphatase
Hydrolysis of phosphate ethers (take phosphate off)
Decarboxylase
Removes Carboxylic acid group as CO2
Deaminase
Removes amino group
Synthase
Synthesizes a new molecule
Carboxylase
Adds carbon dioxide to a molecule (makes Carboxylic acid)
How enzymes work
> substrate fits into active site
change it shape to make reactions happen
bonds broken & new bonds are made
product released
Catalysis
>enzymes act as a catalyst because they can: •bring substrate together •hold substrate •provide acidic or basic groups •induce strains in bonds
Enzyme reaction rate depends on:
> substrate concentration(more enzymes faster reaction)
temperature (increases with increasing temp)
pH
Feedback control
Product inhibits the first enzymes pathways
{1>2>3>4} 4 inhibits #1
Allosteric control
Built in regulatory site different from active site.”anything else”
Inhibition
Reversible :non covalent
irreversible :covalent (permanently attached) ex: penicillin
Competitive/ non competitive reversible inhibition
“Active site”
Reversible competitive : inhibitor bind to active site and compete w/substrate reversible non competitive:inhibitors bind to enzyme not @ active site; often used as medicine
Population dynamics
Enzyme inhibition occurs in a population of many identical molecules.
When an inhibitor bind to enzyme it become inactive, while others are still active.
Enzyme regulation
Regulated by:
•Removal of of covalent bonded part of enzyme [zymogens]
•addition/removal of phosphate groups[phosphorylation]
Zymogens (pro enzymes)
Enzymes are made inactive in in order to activate you must “CLEAVE”
Phosphorylation
Most common
Addition of phosphate causes a shape change in enzymes that can activate the enzymes
Fat soluble vitamins
A D E & K
- mostly hydrocarbon
- can overdose
- stored in fat
- difficult to remove from body
Vitamin E
Tocopherol :antioxidant that protects membranes from free radical oxygen damage
Water soluble act as:
Coenzymes
Antioxidants
Substances to prevent oxidation
>remove free radicals
> vitamin C E, b-carotene, selenium
>phenols are antioxidants
Minerals
Inorganic ions
>cofactors : metal ions
>most are divalent cations
Vitamins C
Antioxidant; protects aqueous components of body& retires vitamin E
Phosphodiesterase
Breaks down cAMP
Agonist & antagonist
Agonist: activates receptor
Antagonist: prevents/blocks receptor
