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