TR

Metabolism

Overview

  • Metabolism: step by step process by which cells take nutrients from their environment and convert them into sufficient components to double their mass and then become 2 cells
  • All the biochemical reactions that take place in the cell are called its metabolism
    • Each step is coordinated by a specific enzyme
  • Catabolic Pathways
    • Breakdown cellular components
    • Exergonic
  • Anabolic Pathways
    • Synthesis cellular components
    • Endergonic
    • Must be coupled to exergonic reaction

Function of Metabolism

  1. Synthesis and Division
  2. Reproduction
    • Making more cellular materials
    • Requires the production of starting materials

5 Metabolic Tasks Necessary For A Cell To Synthesize All Other Cellular Components

  1. Bringing nutrients into the cell

  2. Catabolism: converting nutrients into a group of organic compounds which serve as a starting point to synthesize all other cellular components

    1. 12 precursor metabolites
    2. ATP
    3. Reducing power ie:  NADH

  3. Biosynthesis

    • Making small molecules the cell needs

  4. Polymerization

    • To form macromolecules

  5. Assembly

Catabolic Reactions

  • Breakdown of reactants
  • Used for recycling building blocks
  • Used for energy to drive endergonic reactions
    • Energy stored in intermediates such as ATP, NADH

Anabolic Reactions

  • Biosynthetic reactions
  • Make large macromolecules or smaller molecules not available from food
  • Require energy inputs from intermediates (NADH or ATP) to drive reactions

Two Ways to Make ATP

  1. Substrate-level Phosphorylation (one to one tradeoff)
    • Enzyme directly transfers phosphate from one molecule to another molecule
  2. Chemiosmosis (many molecules of ATP per molecule of glucose)
    • Energy stored in an electrochemical gradient is used to make ATP from ADP and Pi

Redox Reaction

  • Electron removed from one molecule is added to another
  • Oxidation: removal of electrons
  • Reduction: addition of electrons

NADH

  • Electrons removed by oxidation of organic molecules are used to create energy intermediates like NADH
  • NAD+  Nicotinamide adenine dinucleotide
  • NADH useful in two ways:
    • Releases a lot of energy when oxidized that can be used to make ATP
    • Can donate electrons during synthesis reactions to energize them