Metabolism: Fueling Cell Growth - Lecture Slides | BIOL 2111, Study notes of Microbiology

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Metabolism:

Fueling Cell Growth

Chapter 6

Metabolism

• (^) Cells must accomplish two fundamental tasks

to grow

• (^) Synthesize new components
  • (^) biosynthesis
• (^) Harvest energy
• (^) The sum total of chemical reactions of

biosynthesis and energy-harvesting is termed

metabolism

• (^) Energy defined as capacity to do work
• (^) Exists as
  • (^) Potential energy
    • (^) Stored energy
  • (^) Kinetic energy
    • (^) Energy in motion

» Doing work

Harvesting energy

• (^) Amount of energy available released from bonds is

free energy

• (^) Energy available to do work
  • (^) If reactants have more free energy than

products, energy is released

• (^) If products have more energy than reactants,

energy is consumed

Central Metabolic Pathways

• (^) Pathways modify organic molecules to form
  • (^) High energy intermediates to synthesize ATP
  • (^) Intermediates to generate reducing power
  • (^) Intermediates and end products as precursor metabolites
• (^) Pathways  (^) Glycolysis  (^) Pentose Phosphate Pathway  (^) Tricarboxylic Acid Cycle

Scheme of Metabolism

Fermentation

• (^) Used by organisms that cannot respire
  • (^) Due to lack of suitable inorganic electron acceptor or lack of electron transport chain
  • (^) Fermentation stops short of oxidizing glucose or other organic compounds completely, and instead uses an organic intermediate such as pyruvate or a derivative as an electron acceptor
  • (^) Fermentation is partial oxidation of glucose, produces very little ATP; ATP produced only in glycolysis

End products of fermentation pathways E. coli

Chemolithotrophs

• (^) Chemolithotrophs able to use reduced inorganic chemicals as source of energy
• (^) These organisms fall into four groups
  • (^) Hydrogen bacteria
    • (^) Oxidize hydrogen gas
  • (^) Sulfur bacteria
    • (^) Oxidize hydrogen sulfide (H 2 S)
  • (^) Iron bacteria
    • (^) Oxidize reduced iron
  • (^) Nitrifying bacteria
    • (^) Two groups
      • (^) One oxidizes ammonia (NH 3 ) to nitrite
      • (^) One oxidizes nitrite (NO 2 −) to nitrate (NO 3 −)

• (^) Chemolithotrophs generate ATP through oxidative

phosphorylation

• (^) Organisms thrive in specific environments
  • (^) Particularly where reduced inorganic compounds are found
• (^) Do not require external carbon source
  • (^) Produce organic carbon from inorganic source through carbon fixation (Carbon dioxide converted to organic carbon)

• (^) Pigments include
  • (^) Chlorophyll
    • (^) Found in plants, algae and cyanobacteria
  • (^) Bacteriochlorophylls
    • (^) Found in purple and green photosynthetic bacteria
  • (^) Accessory pigments
  • (^) Reaction center pigments
    • (^) Function as electron donors
  • (^) Antennae pigments

Photosynthetic organisms highly visible due

to light capturing pigments

• (^) Light reactions accomplish two tasks
  • (^) Synthesize ATP through photophosphorylation
  • (^) Generate reducing power to fix carbon dioxide

Anabolic Pathways

• (^) Synthesis of subunits from precursor metabolites
  • (^) Pathways consume ATP, reducing power and precursor metabolites
  • (^) Make macromolecules once subunits are synthesized
  • (^) Different macromolecules can be joined to form the structures making up the cell
• (^) Lipid synthesis
• (^) Amino acid synthesis
• (^) Nucleotide synthesis

Nucleotides are composed of three units

1. Nitrogenous base

• (^) Purine (adenine and guanine) – A, G
• (^) Pyrimidine (thymine and cytosine) – T, C

2. 5-carbon sugar molecule (deoxyribose)
3. Phosphate molecule

Nucleotides bond covalently between the 5’PO 4 of one nucleotide and the 3’OH of another

DNA made up of deoxy-ribo-nucleotides