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AP Bio Unit 3

1.1 Enzymes & Energy

Enzymes

  • Metabolic pathways build and break down products, storing and releasing energy

  • Enzymes are proteins that facilitate and catalyze chemical reactions by lowering activation energy

  • Makes process happen more frequently not necessarily faster

  • Enzymes occur with specific substrates

  • Enzymes are named for the reaction they catalyze and almost always end in -ase

  • Enzymes bind with the polymer, puts pressure on the connection using energy, and breaks it

  • Creates a favorable environment

  • Forms temporary covalent bonds with substrate molecules

  • ^ Temperature = ^ Rate of reactions (Frequency of enzyme/substrate collisions)

  • Denaturation: Irreversible shape change caused by unfavorable environment

  • pH can disrupt hydrogen bonds that provide enzyme structure

  • Concentration effects reaction rate: When point of saturation is reached, all enzymes are occupied/in use

  • Enzymes can be inhibited to stop overproduction, or if there are just too many substrates

    • Competitive: bind to active site of enzyme, block substrate

    • Noncompetitive: Bind to allosteric site, change function of enzyme so substrate can’t bind

    • Fastness: no inhibitor>competitive>noncompetitive

Energy

  • Systems tend towards disorder

  • Entropy: measure of randomness in a system

  • Living systems constantly work against entropy which takes energy

  • Two enzyme mediated processes

    • Exergonic processes: activation energy needed to start reaction, energy released, favorable

    • Endergonic processes: activation energy needed to start reaction, energy stored in products, decrease entropy, unfavorable, do not occur spontaneously

  • Anabolic: small molecules combined into large, energy required

  • Catabolic: large molecules broken into small, energy released

  • Coupling: Using exergonic reactions to have energy for an endergonic reaction

  • Remember LEO GER:

    • LEO= Less Electrons : Oxidation

    • GER= Gain Electrons : Reduction

1.2 Photosynthesis

  • Occurs in chloroplasts

  • E.C.

  • Inputs: H2O, CO2, light

  • Outputs: Glucose, ATP, Oxygen

  • Thylakoid: inner

  • Lumen: inside thylakoid

  • Stroma: Outside thylakoid

  • *NADPH (P for plants)

  • Electron Transport Chain (Light Dependent Reaction):

    • Proton pump sends H+ from stroma into lumen, making a higher H+ concentration inside the thylakoid

      • Oxygen is released as a byproduct

      • Oxygen diffuses out of chloroplast because it is small and nonpolar

    • In PS2, an electron from H20 jumps after being excited by light. It jumps from PS2 > proton pump > PS1. The electron is now tired, and regains energy through more light.

    • The electron jumps to the NADP reductase

      • Reduces NADP+ (electron carrier) & H+ into NADPH

    • H+ wants to leave lumen and return to stroma, so it goes through ATP synthase

      • Uses energy to turn ADP & P into ATP (Phosphorylation)

  • Calvin Cycle (Light Dependent Reaction):

    • Carbon fixation: CO2 becomes C6H12O6 (Glucose)

    • Highly endergonic

1.3 Cellular Respiration

  • Occurs in mitochondria

  • G.K.E.A

  • Matrix: Middle

  • Intermembrane space: Outer

  • Cytosol: Outside the mitochondria

  • Inputs: ATP, Glucose, Oxygen

  • Outputs: H2O, CO2

  • Glycolysis:

    • OUTSIDE OF CELL: Glucose is broken into 2 pyruvate

      • Exergonic reaction, produces 2 ATP from 2 ADP + P

    • NADH is broken into NAD+ & H+ (electron carrier)

  • Krebs Cycle:

    • IN MATRIX: 2 pyruvate are converted into CO2

    • ADP & P are combined to ATP

    • NAD+ & H+ and FAD+ & H2 are combined to become NADH and FADH2

  • Electron Transport Chain:

    • Proton pump pushes H+ OUT of matrix, creating higher H+ concentration in the intermembrane space

    • Cell uses newly received NADH, NADH, and FADH2 to contribute electrons that jump over proton pumps

  • ATP Synthase

    • H+ wants to re enter matrix; movement of H+ back and forth through ATP synthase gives electrons energy

    • Oxygen is electron acceptor. Electrons attach to H+ which float to O2, creating H2O

In Anaerobic Cellular Respiration:

  • NADH(electron carrier) from glycolysis has nowhere to go, since usually it would go to O2(electron acceptor)

  • NAD+ & H+ lessens and NADH grows abundantly with nowhere to go

  • Fermentation:

    • Pyruvate from glycolysis act as electron acceptors for NADH. Process continues as normal. Results in lactic acid or alcohol (waste).