AP Bio: Unit 5 - Enzymes & Thermodynamics

Thermodynamics

Thermodynamics

flow and transformation of energy

Photosynthesis

endergonic rx – takes in energy to convert small & simple to large & complex

Respiration

exergonic b/c convert large & complex to small & simple 

carbs + oxygen =

kinetic energy

First Law of Thermodynamics

energy can neither be created nor destroyed, only altered in form

(ex: light to chemical energy)

Second Law of Thermodynamics

As energy changes form, disorder increases (entropy) energy becomes less useful

Free Energy

the amount of energy available to break existing bonds and form new ones

G = H - S

Free energy = Enthalpy (energy in bonds) - Entropy (energy lost to disorder)

Exergonic Reactions

energy out/released, low energy in bonds, high in disorder, negative quantity of free energy

Endergonic Reactions

energy in/must be supplied to be absorbed, high energy in bonds, low in disorder, positive quantity of free energy

Enzymes

Molecules made of protein that help biological reactions occur at normal temps and pH by bringing 2 molecules into alignment so they can bond OR stressing a bond so it takes less energy to break it

Enzymes lower

activation energy

Activation Energy

energy required to get a reaction to begin

REVIEW GRAPHS

YES MA’AM

The shape of the active site must

fit the substrate

Induced fit

contact of substrate with active site induces a shape change in the protein so it fits the substrate even better

Enzymes are specific to their substrate because

of the shape of the active site and some can only run 1 substrate in 1 direction

Enzyme is ___________ by reaction so it can be reused.

unchanged

Rate of Reaction

how much substrate can be bound and acted upon in a given time period

 Initial rate is

fast because the enzyme is catalyzing as fast as it can and there are many enzymes w/empty active sites, also depends on enzyme concentration; it slows as the amount of product increases and substrate decreases 

What affects of enzymes?

Temperature, pH, inhibitors, enzyme concentration, substrate concentration

Temperature

increases rate of reaction (due to increased molecular motion) to a certain point (optimum) but then the protein denatures

pH

increases rate to the optimum but then H+/OH- ions interfere with H-bonding in protein and it unfolds

Inhibitors

 another molecule interferes with substrate at active site

Competitive inhibitors

binds at active site so substrate cannot bind there, antibiotics interfere with bacterial enzymes this way 

Non-competitive/allosteric inhibitors

binds at another site on the enzyme so it changes shape of the active site so substrate can’t bind

Utilize other resources to study (Khan Academy, AP Classroom, etc.)

Oui