L10-11: Bioenergetics + Enzymes Flashcards
Biological work: Synthetic
changes in chemical bonds
ex. formation of new chemical bonds/ synthesis of new molecules
Biological work: mechanical
changes in the location/ orientation of a cell or subcellular structure
ex. physical change in position/orientation of cell
(movement of organelles/ vesicles along microtubules)
Biological work: concentration
movement of molecules across a membrane against a concentration gradient (low->high)
ex. the accumulation of digestive enzymes into secretory vesicles to be released as food is digested
biological work: Electrical
movement of ions across a membrane against electrochemical gradient
ex. ions are transported->a charged difference in the membrane
(the difference of H+ in mitochondria/chloroplast membrane for atp/ pumping Na+ & K+ in/out
biological work: heat
a useful increase in temperature
ex. homeotherm (self-regulate heat)
biological work: bioluminescence
production of light
-aka fluorescence: the production of light following absorption of light of a shorter wavelength
ex. using atp/ chemical oxidation
fireflies, jellyfish, mushrooms
First Law of Thermodynamics
in every physical/ chemical change, energy in the universe is constant
*Although the form may change, but energy can never be replaced/ destroyed
Second Law of Thermodynamics
the entropy of the universe increase= the capacity of a sys. to do work and will decrease
h= g+ ts
h: total energy
g: free energy (available to do work)
s: entropy (a measure of chaos, not available to do work)
t: temperature in degrees (K)
activation energy
the energy required to break bonds and start a reaction
*biological systems are metastable because of this
-G
energy available to do work
+G
energy not available to do work
exergonic
exergy is EXited/ released
reactants: more energy
products: less energy
G<0
example: ATP-> ADP+Pi (hydrolysis)
endergonic
energy is ENtered/ consumed
reactants: less energy
products: more energy
G>0
example: ADP+Pi-> ATP (regeneration)
what is the energy level in catalyzed reactions?
an uncatalyzed reaction requires a HIGHER activation energy than a catalyzed reaction
-no difference in free energy
absolute energy
atp hydrolysis
start:
ATP
H=G(high) + TS (low)
-G
End:
ADP+Pi
H=G(low) + TS (high)
+G
Keq
the ratio of product concentrations to reactant concentration of equilibrium
Protein folding
folding: -G (spontaneously)
unfolding: +G (require energy to unfold as it is not spontaneous)
Eduard Buchner
in 1897
discovered that yeast extracts could ferment sugar to alcohol
fermentation is promoted by molecules that continued to function when removed from cells
James Summer
1926
isolated & crystalized protein-> crystals only contain proteins= all enzymes are proteins
JBS Haldane
1930s
weak bonding interactions between an enzyme and its substrate might be used to catalyze a reaction
enzymes
catalysts in biological systems
proteins
ex. ritonavir inhibits HIV protease where it stops viruses from replicating
transition energy
reactant needs to reach this stage, where the reactants hs free energy higher than the products
=not stable because reactant molecules don’t stay there for long
thermal activation
increases average energy of all molecules
catalyst
an agent that enhances the rate of the reaction by lowering the activation energy
characteristics of enzymes
group specific
substrate specific
remain unchanged unless denatured
induced fit model
a substrate binds to an active site and both change shape slightly, creating an ideal fit for catalysis
ex. hexokinase & D glucose
monkeys and peanuts
monkey: enzymes
substrate: peanuts
products: the shells & the inside
reaction rates
The rate of an enzyme-catalyzed reaction increases with an increase in the concentration of an enzyme.
maximum velocity
levels off because enzymes are limited where there is a higher substrate concentration
types of enzymes regulations
- feedback inhibition
- allosteric regulation
- covalent modifications
feedback inhibition
an enzyme’s activity is inhibited by the enzyme’s end product.
competitive inhibition
the inhibitor binds to the active site
=competes w/ substrate for binding= no products
noncompetitive inhibition
the inhibitor binds to another site of the enzyme, but distort products
substrate is able to bind to the active site but does not produce products
allosteric inhibition
enzyme is active
->inhibitor binds to the allosteric site, changes the shape of an enzyme
->substrate cannot bind=no products
enzyme is inactive
allosteric activation
enzyme is inactive
->activator binds to the allosteric site, changes the shape of an enzymes
->substrate can bind= product formation
enzyme is active
phosphorylation
adding a phosphate group
dephosphorylation
removing a phosphate group
proteolytic cleavage
some enzymes are precursors, where the cleavage is removed to become functional
