Biochemical Reactions and Enzymatic Action Study Notes

Activation Energy and Enzymes

• Activation Energy: The minimum energy required to start a chemical reaction.

  • Necessary to perpetuate or carry out a reaction.
  • Heat can be damaging to proteins, which is a relevant consideration in chemical reactions.

• Role of Enzymes: Enzymes lower the activation energy barrier, facilitating biochemical reactions without being completely consumed.

  • Note: The lowering of the activation energy does not imply it is completely reduced; enzymes can still function under various conditions.
  • Mechanisms: While the biochemical action of enzymes is recognized, the precise methods they employ to perpetuate reactions are still being studied.

Enzyme-Substrate Interaction

• Enzyme Saturation: When all active sites on an enzyme are occupied by substrates, the enzyme is said to be saturated.

  • This leads to the formation of an enzyme-substrate complex.

• Example of Hydrolysis: Using sucrose as a substrate, we see it separating into fructose and glucose.

  • The bonds between fructose and glucose are stressed during reaction processing.
  • This leads to the release of glucose and fructose as separate molecules due to physical stressors on the bond.

• Reactants Combining: Similarly, if reactants need to be combined rather than separated, similar physical stresses can be applied to destabilize those reactants, making them more reactive.

Enzyme Existence and Gene Coding

• The exact number of enzymes present in the human body at any time is unclear.
  • Estimates vary widely, and this remains an area of ongoing research.
  • Genetic Understanding: Historically, it was believed that one gene encoded one enzyme, but findings from the Human Genome Project revealed that multiple enzymes can arise from one gene.

Enzyme Cofactors and Inhibitors

• Environmental Factors: Enzyme cofactors can influence enzyme activity depending on local environmental conditions.

• Enzyme Inhibitors: These are mostly proteins that inhibit enzymatic action.

  • They can be classified into two types:
    1. Competitive Inhibitors:
       • Definition: Compounds that mimic the shape and structure of the substrate and bind to the enzyme's active site.
       • Mechanism: When a competitive inhibitor occupies the active site, the actual substrate cannot bind, preventing enzyme activity.
       • Examples: Penicillin (an antibiotic) and DDT (dichloro-diphenyl-trichloroethane), both act as competitive inhibitors.
         • DDT History: Originally shelved, it was reformulated by chemist Mueller around 1948 and became widely used from the 1940s to the 1960s but eventually was recognized for the environmental damages it caused, leading to Rachel Carson's work on "Silent Spring" connecting pesticide use to ecological decline.
    2. Noncompetitive Inhibitors:
       • Definition: Inhibitors that attach to an enzyme not at the active site but on a different surface, altering the enzyme's shape and function.

Cellular Respiration and Energy Production

• Cellular Fuel: Glucose is utilized as the primary fuel source in the presence of oxygen.

  • Requires a chemical equation of the form:
    $ext{C}<em>6 ext{H}</em>{12} ext{O}_6 + 6 ext{O}_2$
  • This indicates that one molecule of glucose reacts with six molecules of oxygen.

• Goal of Cellular Respiration: The primary goal is to produce ATP.

  • Roughly 33-34% of tissue energy is derived from glucose, which means out of approximately 686 kilocalories theoretically available from glucose, about a third is converted to ATP.
  • The rest of the energy flow relates to the movement of electrons throughout the biochemical processes involved in respiration.

• Key Processes:

  • Reduction: The gain of electrons by atoms or molecules.
  • Oxidation: The loss of electrons by atoms or molecules.
  • These processes are critical and will be explored further in the discussions on aerobic cellular respiration and the associated biochemical equations.