Chapter 6: Metabolism: Fueling Cell Growth

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Chapter 6MetabolismFueling CellGrowth
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Chapter 6 Notes

• Dont worry too much about the details of
  Glycolysis, Cellular Respiration, or
  Photosynthesis onward.
• These topics are covered on pp. 144-151 and pp.
  156-163.
• Note, however, that we will cover Glycolysis and
  Cellular Respiration in class at least from the
  perspectives of the importance of NAD
  regeneration.

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Important Point
If you are having trouble understanding lecture
material Try reading your text before
attending lectures. And take the time to read it
well!
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Products of Microbial Metabolism
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Important Consequencesof Microbial Metabolism

• Beer, wine, and other alcoholic beverages.
• Bread (all of above are mostly products of the
  yeast Saccharomyces cerevisiae).
• Products of lactic-acid bacteria (LAB) including
  sour milks, various cheeses, half-sour pickles,
  sauerkraut, etc. (e.g., of Lactococcus spp.
  Lactobacillus spp.).
• Organic solvents including acetone (product of
  Clostridium acetobutylicum), butanol (ditto),
  and, of course, ethanol (product of S.
  cerevisiae).
• Acetic acid (vinegar).
• Biochemical identification of bacterial species.
• Unique (e.g., not found in animals) targets for
  antimicrobial action.
• Disease (e.g., dental caries).

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Metabolism Catabolism Anabolism
sum metabolism
Pay particular attention to those words in bold
in this figure.
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Bioenergetics (see Fig. 6.3)
More generally, sun or reduced inorganic
chemicals (ocean vents).
More generally, photoautotrophs (or just
autotrophs).
E.g., glucose
More generally, chemoheterotrophs.
Note that bacteria dont have mitochondria
aerobic bacteria are mitochondria!
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Metabolism Terms Concepts

• Metabolic pathway highly evolved intracellular
  sequence of chemical reactions.
• Each step of a metabolic pathway usually is
  enzymatically catalyzed (and enzymes are
  proteins).
• Substrates are molecules that enter into
  enzymatically catalyzed reactions.
• Products are what substrates are enzymatically
  converted into.
• Enzymes typically are very precise in terms of
  what substrates they will accept (often no more
  than one specific chemical) and they will convert
  a substrate into (often no more than one specific
  chemical).
• Precursor molecules are found at the start of
  metabolic pathways.
• Intermediate molecules are found within metabolic
  pathways.
• End products are the molecules ultimately
  produced by a given metabolic pathway.

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Chemical Energetics
How cells burn glucose.
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Enzyme Terms Concepts

• Enzyme names generally are indicated by an -ase
  ending, e.g., dehydrogenase (lysozyme is
  exception).
• Enzymes have active sites (a.k.a., catalytic
  sites).
• Cofactors are non-protein components of enzymes
  they can be organic or inorganic.
• Coenzymes are organic cofactors they generally
  are carriers of other molecules or ions.
• NAD for example is a coenzyme.

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Ezyme with Cofactor
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Environment Impact on Enzyme Activity
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Enyzmatic Inhibition
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Variation on Metabolic Pathways
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Variation on Metabolic Pathways
Glycolysis is a catabolic pathway.
Krebs citric acid cycle is a cyclic catabolic
pathway.
E.g., ATP, CO2, and NADH.
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ATP Energy Currency of Cells
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ATP, ADP, and Metabolism
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Oxidation-Reduction (Redox)
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Oxidation-Reduction (Redox)
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Oxidation-Reduction (Redox)
Note that 2 hydrogen ions are removed along with
the 2 electrons (only one H ends up attached to
NAD, hence the charge change).
Note NAD (not NAD).
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Overview of Metabolism
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Glycolysis (see Fig. 6.14) An Enzyme and
Coenzyme Mediated Catabolic Pathway
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Glycolysis (see Fig. 6.14) An Enzyme and
Coenzyme Mediated Catabolic Pathway
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Glycolysis (see Fig. 6.14) An Enzyme and
Coenzyme Mediated Catabolic Pathway
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Regeneration of NAD
Fermenation Pathways
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Regeneration of NAD
E.g., see Fig. 6.17-6.19 (6.16-6.18)
Cellular Respiration
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Regeneration of NAD
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above is why aerobes need O2
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Lactic Acid Fermentation (see Fig. 6.20)
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Ethanol Fermentation (see Fig. 6.20)
No, These are Not Lemons!
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Simple Fermentation Pathways
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Mixed-Acid Fermentation
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Other Fermentation Pathways
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Other Fermentation Pathways
Beer, wine, bread.
Flatulence!
Swiss cheese.
LAB our own muscles.
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Anaerobic Respiration
employs an inorganic molecule other than O2 as a
terminal electron acceptor.
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Hydrolytic Enzymes

• Amylases enzmes that hydrolyze starches to
  their constituent glucoser subunits.
• Disaccharidases enzymes that hydrolyze
  dissacharides to constituent monosaccharides.
• ?-galactisidase is the most famous of
  disaccharidases it breaks down the sugar lactose
  (into galactose and glucose).
• Lipases enzymes that hydrolyze fats (into
  glycerol or and fatty acids).
• Proteases enzymes that break down proteins.
• Deaminases enzymes that remove amino groups
  from individual amino acids.
• The resulting products can be used as
  alternatives to glucose as carbon and energy
  sources.
• Chemolithotrophs (a.k.a., chemoautotrophs)
  utilize substances other than organic compounds
  as energy sources and get their organic carbon
  from CO2.

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