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

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