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55 Cards in this Set
- Front
- Back
- 3rd side (hint)
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steady states
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reactions inside cells are coupled to other reactions and are driven by the constant removal of their products
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most cells are not at equilibrium but what?
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steady state
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a cell alive : atp is what
a cell dead : atp is what? |
atp high when cell alive
atp low when cell is dead |
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do reactions with -ΔG occur at great rate
y or why not? |
no...only if catalyzed by enzyme
most reactant molecules do not have enough thermal or kinetic energy to overcome a barrier for reaction called activation energy Ea |
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enymes do what?
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lower activation energy
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can enzymes make a reaction occur spontaneously if it is thermodynamically unfavourable?
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no
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do enzymes alter concentrations of reactants and products
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no
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can enzymes extract more useful energy per mole of reactants
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no they only extract it faster
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as a catalyst an enzyme also...
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is only required in small amounts
must be left unchanged at the end of a reaction so that it can cycle back to bind more substrate |
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enzymes increase rate of a reaction how much
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10^8 to 10^12 fold
or 1s vs 300000 years |
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enzymes are what with respect to substrates?
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highly specific
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4 enzyme classes
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oxy-reductases- catalyze oxidation reduction reactions
isomerases-let molecule go through 2 isomeres transferases-transfer functional groups ligases-joining |
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substrates bind to an enzymes active site by what?
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weak bonds
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Active site is formed from a cluster of
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amino acids that are not usually next to one another on the polypeptide chain of the enzyme
These amino acids come together to form a pocket or groove that binds the substrate (s) with high specificity and moderate affinity |
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secondary and tertiary structure are vital for enzymes for what?
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positions amino acids to form the active site
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what is crucial with respect to enzymes
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temperature, ph, ionic conditions
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do enzymes always have to act on 1 substrate?
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no they can act on different substrates with similar functional groups
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prostetic groups
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non-protein molecules which aid catalysis
organo-metal compounds in metal can donate/accept electrons to/from the substrate |
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chromophores
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small organic molecules which absorb light
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cofactors
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metal ions on their own, like Mg2+ that can function as aids in catalysis or binding of the substrate
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how does enzyme fit
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induced-fit hypothesis- enzyme folds around substrate to some extent
R-groups interact with substrate |
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what can substrate distortion during folding do?
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weaken specific bonds in substrate
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enzyme mechanisms of catalysis
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1)enabling a favourbable orientation between substrate molecules
2)changing substrate reactivity -formation of covalent bonds between R-groups in active site and substrate will speed up reaction -acceptence or donation of electrons can speed up by strenghtening or weakining bonds -ionic interactions...cofactor can bind to substrate and cause it to acquire charge 3)strain on substrate: weakens bonds |
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what happens when product is formed from enzyme-substrate reaction
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-temporary covalent bonds are broken..
electrons and protons are restored to the enzyme or substrate enzyme unfolds to release the product, with which it no longer has an energetically favorable interaction |
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pH determined what?
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H+ concentration
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What can charge on R groups do to a small extent
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determine secondary and tertiary structure
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proton exchange and interaction of charged groups is sometimes what in catalysis?
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intermediate step
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pepsin
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stomach digestive enzyme...most active at pH3
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3 pepsis in stomach
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trypsin
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intestine-most active pH8
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don't trip in the intestine or you will go down 8 flights
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what happens to enzymes as temperature increases
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more substrate molecules gain sufficient energy from thermal sources to overcome Ea
but at high temperature, enzymes denature |
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many enzymes can be what? (structure)
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crystalized
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substrate molecules can be released inside the enzyme crystal from ? give definition
what is this good for? |
photochemical cages (molecules that inactivate or surround the substrate , but release it upon a pulse of light from a laser
can be used to take pictures by x-ray crystalogrophy |
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what can site directed mutations of R-groups test?
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can test for involvement of R-groups or trap reaction at certain stage
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what is a way in which the enzyme-substrate complex can be stabilized
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sudden cooling
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michaelis-menten equation parts to know
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E + S <>ES <>E + P
E + S <>ES >E + P now add rate constants k1,k-1, and k3 V = Vmax. [S] / ([S] + KM) |
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michaeli-menton equation definition
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relates initial velocity of product formation per mole of enzyme present, V
to the substrate concentration |
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vmax
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when S is saturating and almost all E is present as ES
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Vmax units
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number of molecules of substrate that can be converted to product per second
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michaelis-menten reaction is in what state
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steady state
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Vmax equals what?
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Vmax= total [E] . k3
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how to find Km
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use 1/2 vmax and draw square
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Km equals what?
definition |
1/affinity of enzyme for substrate
high kM equals low affinity low kM equals high affinity |
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draw michaelis menten graph
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draw it
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enzyme inhibitors
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1)irreversible inhibitors
-covalently bond to an amino acid residue...lower vMax 2)reversible inhibitors a)competive -bind to active site and compete with substrate...increase Km...does not reduce Vmax b)non competitive basic -binds away from active site -lowers vmax, does not change Km -lowers catalytic efficiency c)non-competitive different(allosteric) inhibition -binds to regulatory subunit and lowers catalytic efficiency - |
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allosteric can be what?
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both inhibitors and activators
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phosporylation of enzymes at specific sites can do what?
caused by what enzymes? |
stimulate or inhibit activity
kinases |
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catabolic
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disassembly of complex molecules to simpler ones
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anabolic
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synthesis of more complex molecules
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catabolic pathways do what?
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release energy that can be stored
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oxidized vs. reduction
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oil rig
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1 form of oxidation not normally though of
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loss of partial electronic charge
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why is oxidation of hydrocarbons so lucrative?
how is this done |
releases a huge amount of energy
strip H atoms from metabolites and combine them with O2 to make water -56 delta G |
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oxidation of glucose equation and purpose
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C6H12O6>6CO2+6H20
ΔGo== -686 can make atp ADP+Pi> ATP ΔG=+ 11.5 kcal per mole under cellular conditions, concs. |
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atp definition
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main short term store of chemical energy
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how does atp work
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1) 4 OH groups are deprotonated at neutral pH
2)2 terminal phosphoanhydride bonds are high energy 3)releases energy when these bonds are split 4)energy release is due to removal of negative charge and increase resonance stabalization in Pi vs. P attached to ATP |
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