Energy, Catalysis and Biosynthesis

first law of thermodynamics

• energy cant be created or destroyed

• energy cant be transferred and change forms

second law of thermodynamics

• entropy (disorder) is always increasing

  • movement towards disorder is a spontaneous process

• no energy transfer is 100% efficient

  • some energy is lost as heat

• cells remain organized but do not defy the 2nd law (because the environment becomes disordered)

  • take in energy, generate order within

  • nonliving things do not have order

catabolism

turning food molecules into polymers (building blocks) for biosynthesis

• ½ of metabolism

• -∆G (exothermic)

• energy and heat released

  • more energetically favorable

anabolism

turning polymers into molecules the cell will use

• ½ of metabolism

• +∆G (endothermic)

• energy required

  • less energetically favorable

oxidation

loss of electrons

• cells obtain energy by the oxidation of organic molecules

• ex: C binding to O (O is more electroneg than C)

reduction

gain of electrons

• occurs as # of C-H bonds increases (H is less electroneg than C)

michaelis-menten kinetics

• very low substrate: velocity is proportional to substrate conc. (linear proportion of graph)

• very high substrate: velocity is not dependent on substrate conc. (Vmax)

michaelis constant ([S]=Km)

substrate conc. where the rxn proceeds at ½ maximum velocity

free energy (G)

usable energy of a system

free energy change (∆G)

determines whether a rxn can occur

• -∆G: exothermic, energetically favorable

• +∆G: endothermic, energetically unfavorable

• dependent on concentration of substrates and products

standard change in free energy (∆G°)

used to compare relative energy of different rxns

competitive inhibitors

bind at same site as substrate

• increase Km

• no change to Vmax

non-competitive inhibitors

binds at a site other than active site

• lowers Vmax

• no change to Km

equilibrium constant (K)

ratio of substrate to product at equilibrium

• proportional to ∆G°

• measure of directionality

• indicates strength of molecular interactions

equilibrium

rate of forward rxn = rate of backward rxn

• association rate (Kon) = dissociation rate (Koff)

activated carrier molecule

stores & transports energy within a cell

• required for biosynthesis

• widely used in metabolism

• ATP is the most widely used

NADH

activated carrier of electrons

• type of activated carrier molecule

• nucleotide

• catabolic rxns

NADPH

activated carrier of electrons

• type of activated carrier molecule

• nucleotide

• biosynthesis (photosynthesis)

ATP hydrolysis

• often tied to phosphorylation of another molecule

• can aid in energetically unfavorable rxns

• can lead to pyrophosphate formation

• can synthesize nucleic acids