AP BIO: Enzymes

  • Metabolic pathways

    • catabolic: degradative pathways

    • anabolic: biosynthetic pathways

  • Forms of energy

    • Kinetic: thermal energy transfers

    • Potential: chemical → energy trapped in food

  • Laws of Thermodynamics

    • First law: Energy cannot be created or destroyed; only transferred or transformed

    • Second law: entropy (disorder) in the universe is constantly increasing

  • Changes in the amount of free energy available change the pop. size and disrupts ecosystem

  • Methods to capture, use, and store free energy have evolved

  • Life requires a highly ordered system

  • Living systems do not violate the 2nd law of Thermo.

    • order maintained through coupling endothermic (pos change) rxns w/ exothermic rxns (neg change)

    • Energy input must exceed free energy lost to maintain order & power cellular processes.

    • Organisms use free energy to grow, reproduce, and maintain themselves

  • Body temp. and metabolism (endotherms vs ectotherms)

  • reproduction and rearing of offspring (k vs r)

  • smaller the organism = higher the metabolic rate

  • excess free energy = storage and growth

  • insufficient free energy = less mass, death

  • ATP is the energy currency of life (adenosine triphosphate)

    • adenine, ribose, and three phosphates

    • ADP is formed when ATP loses one phosphate (molecule that gains phosphate is phosphorylated)

Enzymes speeds up rxns

  • Enzymes are protein catalysts (lowers activation energy to speed up rxn)

  • For a rxn to proceed the reactants must reach the transition state

Basic Enzyme Structure

  • Substrate: Reactant

  • Active site: where the substrate binds (lock and key)

  • induced fit: shape of the active site changes because of the substrate

  • substrates enter active → substrates are held by weak bonds (ionic & hydrogen) →Active site lowers act. energy (speeds up rxn) → substrates are converted to products→ products released → active site becomes available for two sub. molecules

Inhibition of Enzymes

  • Non-competitive inhibitors: bind to inactive parts of the enzyme so the active site changes shape, which prevents the substrate from binding

  • Competitive inhibitors: compete with substrates for the active site

  • Allosteric enzymes regulate a pathway (neg. feedback)

    • allo. enzymes are usually 1st or 2nd enzyme in pathway

    • Activators and inhibitors bind to the allo. site which either will or will not reveal the active site

Effects of the Environment

  • Temp.

  • Salinity

  • pH

  • Cofactor: Minerals are inorganic helpers that aid in enzyme activity

  • Coenzymes: vitamins are organic helpers that aid in enzyme activity