Energy Enzymes & Metabolism
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energy of movement
sum total of all chemical reactions in an organism
Complex molecules are made from simple molecules; energy input is required.
Complex molecules are broken down to simpler ones and energy is released.
first law of thermodynamics
Energy is neither created nor destroyed.
When energy is converted from one form to another, the total energy before and after the conversion is the same.
2nd law of thermodynamics
When energy is converted from one form to another, some of that energy becomes unavailable to do work.
No energy transformation is 100% efficient.
measure of the disorder in a system
It takes energy to impose order on a system. Unless energy is applied to a system, it will be randomly arranged or disordered.
- release free energy (- delta G)
- catabolism: complexity decreases
- generates disorder
ex. cell respiration
(page 13 & 19 on slide)
- consume free energy (+ delta G)
- complexity & order increases
ex. active transport, cell movements
(page 14 on slide)
Hydrolysis of ATP is __ & formation of ATP is __
- ATP + H2O > ADP + P + free energy
- ADP + P + free energy > ATP + H2O
(page 17, 18, & 19 on slide)
speed up the rate of a reaction
Most biological catalysts are enzymes that act as a framework in which reactions can take place.
(not altered by the reactions)
__ changes the reactants into unstable forms with higher free energy; the reactants have more kinetic energy
ex. transition state intermediates. can come from heating the system
In an enzyme-substrate complex (ES), the __ binds to the __
substrates; active site
(held together by hydrogen bonds, electrical attraction, or covalent bonds)
The enzyme may change when bound to the substrate, by returns to its original form.
(page 28 on slide)
Binding of a substrate to an active site depends on:
- hydrogen bonds
- attraction & repulsion of electrically charged groups
- hydrophobic interactions
Many enzymes change shape when they bind to the substrate
The rate of a catalyzed reaction (enzymes) depends on __
Concentration of an enzyme is usually much lower than concentration of a substrate.
At saturation, all enzyme is bound to substrate - maximum rate (page 36 on slide)
regulate enzymes & metabolism: molecules that bind to the enzyme & slow reaction rates
Inhibitor bonds noncovalently to the active site & prevents substrate from binding
compete with the natural substrate for binding sites
(When concentration of competitive inhibitor is reduced, it detaches from the active site.)
(page 39 on slide)
bind to the enzyme at a different site (not the active site). The enzyme changes shape and alters the active site.
allosteric (noncompetitive) inhibitors: Changed shape inhibits substrate from binding.
Allosteric activators change the shape of a distorted active site so a substrate can fit.
(page 41 & 46 on slide)
Every enzyme is most active at a particular __ & has an optimal __
pH influences the ionization of functional groups & effects folding and thus enzyme function.
At high temps, noncovalent bonds begin to break. Enzymes can lose its tertiary structure & become denatured.
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