Microbial Metabolism

Chapter 5

Metabolism

A. Metabolism: Is the sum of all chemical reactions in the body.

B. metabolism is divided into two types of classes: catabolism and anabolism.

• Catabolism is the chemical reactions that break down large compounds and release energy.

• Anabolism is the chemical reactions that require energy to build large compound

• Catabolic reactions furnish the energy needed to drive anabolic reactions.

– . Energy harvested from catabolic reactions are stored in ATP molecules. ATP molecules are used to drive many anabolic reactions.

Oxidation Reduction

Energy is often transferred from one molecule to another by oxidationreduction reactions.1.Energy is transferred when electrons from a molecule being oxidized are shifted to a molecule being reduced.

a. Oxidation is the removal of electrons b. Reduction is the gaining of electronsc. Oxidation and reduction always occur together.d. Most microorganisms oxidize carbohydrates as

their primary source of energy.

cellular respiration 1.Cellular respiration oxidizes glucose to

reduce NAD+ to NADH (NADH is an electron carrier)

2. Cellular respiration has three stages, glycolysis, krebs and electron transport.

GlycolysisGlycolysis is an oxidation

reduction reaction.1. Glucose is oxidized to 2 Pyruvic acids.

2. 2NAD+ are reduced to 2 NADH.

3. produce 2 ATP by substrate level phosphorolation

4. Occurs in the cytoplasm of both procaryotes and eucaryotes

Preparatory step

• Preparatory step for Krebs cycle:

• Both pyruvic acid molecules from glycolysis are oxidized into two acetyl CO-A.

• 2 NAD+ are reduced yielding two NADH

• Prep step occurs in the Mitochondria.

Krebs cycle

• Oxidation of 1 acetyl co-A to carbon dioxide produces – 1 molecule of ATP– 3 NADH – 1 FADH

• Occurs in the cytoplasm in procaryotes

• Occurs in the mitochondria in eucaryotes

Electron Transport

• Converts the energy in NADH and FADH molecules into a hydrogen gradient in the mitochondria

Electron Transport– Occurs in the plasma membrane of prokaryotes and

in the inner mitochondrial membrane in eukaryotes.– The hydrogen gradient built up in the mitochondria is

responsible for the production of the most of the ATP in the cell.

Electron Transport

Production of ATPH+ ions pass through ATP synthase stimulating it to

produce ATP from ADP

D A T P yield from procaryotic respiration1. Each N A DH produces enough H + to account for the

production of 3 A T Ps. Each FA DH is w orth 2 A TP sa glycolysis = 8 A T P (6 from 2 N A DH and 2 produced

during glycolysis )b. P reparatory S tep in w hich pyruvic acid is converted

into A cetyl Co-A = 6 A T P (from 2 N A DH )c. Krebs cycle = 18 A T P (from 6 N ADH ) + 4 A T P (from 2

FA DH ) + 2 A T P produced in the cycle.d. T otal = 38 A T P in procaryotese. In eukaryotes it cost the cell 2 A T P to get the 2

m olecules of N A DH produced in glycolysis into them itochondria.

III Fermentation. Organisms produce ATP in the absence ofoxygen.A . Fermentation produces A T P through glycolys is .

1. Ferm entation does not use the krebs cycle or the electrontransport.

2. N ADH is used to reduce pyruvic acid to either lactic acid oralcohol. a. N A DH is converted back to N A D+

Fermintation