Metabolism

• A cell is a miniature factory• A large number of Chemical reactions are

occurring• A (reactants) + B (reactants) ----> C

(products)• Chemical reactions are either endogonic

(req. energy) or exogonic (release energy)

Enzyme

• Reduce Activation energy

• Contain specific active sites

• Substrates bind to active sites, forming the enzyme-substrate complex.

• Enzyme-substrate interaction results in product formation

• For ex. A + B ---> C

Enzymes

• Two types of enzyme-substrate inhibition

• 1.) Competitive – different substrates bind to the same active site.

• 2.) Allosteric – substrates cause the protein to change 3-D shape. Thus, the function changes.

Electron transfer

• Oxidation – when electrons are given up (donation)

• Reduction – when electrons are taken in (accepting)

Metabolism

Catabolism- produce energy (ATP)- breakdown molecules (ex. glycolysis)

Anabolism- use energy (ATP)- synthesize macromolecules (ex. DNA, lipids, etc.)

Metabolic Strategies

All are based on energy, electron and carbon source:1.) Chemoorganotrophic (chemoheterotroph)2.) Chemolithotrophic (chemoautotroph) 3.) Photolithotrophic (photoautotroph)4.) Photoorganotrophic (photoheterotroph)

Metabolism

Catabolism

Energy (ATP)Small molecules (precursors)

Anabolism

Large molecules

Catabolism

- ex. Glycolytic pathway (glycolysis)

- Two types of catabolism:

1.) respiration-aerobic( w/ oxygen)

- anaerobic respiration (w/o oxygen)

2.) fermentation (does not use oxygen)

- Glucose is taken in and broken down in order to generate energy and to use the glucose carbons as a source of carbon.

Glycolysis

TCA Cycle

GlycolysisRespiration Fermentation

Oxidative phosphorylation

Organic products

Respiration

- Three phases

- 1.) Glycolysis

- 2.) TCA cycle

- 3.) oxidative phosphorylation

Fermentation

- Two phases

- 1.) Glycolysis

- 2.) Fermentation -high yield of product, ex. ethanol

Chemical reaction

• Metabolism involves chemical reactions A+B-->C+D, ex. Glycolysis

• Three events – 1.) electron flow – 2.) carbon flow – 3.) energy production

Metabolism

Metabolism

energyelectrons carbon

Binary fission

Flow of

Electron flow

TCA

electrons

e-

Coenzyme - NAD -->NADH

Oxidative phosphorylation(electron transport chain)

Coenzymes - NAD-->NADH NADH

O2

FermentationH2O

NADNADH

NADH->NAD

e-

NADHNAD

Reduction/oxidation (redox)

- Electron flow involves redox reactions.

- Reduction - a molecule accepts an electron. Reduced. Ex. NADH

- Oxidation - a molecule donates an electron. Oxidized. Ex. NAD

- H ion transfer is usually accompanied by electron transfer.

Reduction/Oxidation (Redox)

• Molecules involved in redox reactions• Ex. Coenzymes: (oxidized)NAD+

+ H+ + e- --> NADH (reduced) Occurs in glycolysis, TCA

• Ex. Electron transport chain (electron carriers accept electrons from NADH)

• Ex. 1/2O2 + H2 + e- ---> H2O Final electron acceptor can be oxygen, sulfate, nitrate, carbonate. (S,N, and C are anaerobic respiration)

• Cycling : If both fermentation and respiration are possible, the reduced NADHs are used in the electron transport systems and fermentation. The oxidized NADs are used in respiration and/or fermention.

Glycolysis

TCA Cycle

NADH

NADH

Electron transport chain

(chemiosmosis)

H2OOrganic products

Respiration Fermentation

NADHNAD

NADNADH

Glucose (6 C molecule)

Pyruvic acid (Two 3 C molecule)

TCAIntermediates

(3 or2 C)

Carbon Flow

CO2

Biosynthesis(anabolism)

Intermediates

Glycolysis (Breakdown of glucose)

Glycolysis

Pyruvic acid

TCA Cycle

NADH

NADH

Electron transport chain

(chemiosmosis)

H2OOrganic products

Respiration Fermentation

NADH

CO2

Carbon flow

• Large molecules are broken into smaller molecules (catabolism)

• Critical intermediates are generated (ex. Pyruvic acid, etc.) They are used in the anabolism process as well as entry back into the catabolism process.

Energy Production

• 1.) Substrate-level phosphorylation- ADP + P ==> ATP (associated with glycolysis)

• 2.) Oxidative phosphorylation Ex. electron transport chain associated with the proton motive force.

• 3.) Photophosphorylation – converts light energy to chemical energy of ATP and NADPH. (Light +carbon dioxide+wate =>sugar=>glycolysis)

Substrate Level Phosphorylation

- Occurs at certain steps in glycolysis

- Fermentation generates most of its ATP using this process since no oxidative phosphorylation is present.

- Level of ATP generation is less than oxidative phosphorylation.

- Fermentation:Makes up difference by metabolizing large amounts of material, thus generating large amounts of product.

Oxidative Phosphorylation

- Electron transport chain

- Located in the cytoplasmic membrane

- Transfer of electrons also exports H ions to one side of the membrane, creating a gradient (Proton motive force).

-The H ions re-enter thru an ATPase, generating high levels of ATP. This process is call chemiosmosis

Photophosphorylation

• Light trapping pigments (chlorophylls)

• Sugars are synthesized with energy from light.

• The sugars are then metabolized (glycolysis).

Glycolysis

Glucose

Pyruvic acid

TCA Cycle

NADH

NADH

Electron transport chain

(chemiosmosis)

H2OOrganic products

Respiration Fermentation

ATP

ATP

ATP

ATP

CO2

FADH2

Respiratory Metabolism• Conversion of carbohydrates to pyuvate

– end of glycolysis (EM pathway)

• Oxygen is the final electron acceptor => water

• Includes the TCA cycle

• Includes Oxidative phosphorylation

Summary of Glycolysis (EM)

• Transfer electrons (oxidation-reduction)

• Generates NADH (oxidized)

• Generates small amounts of ATP (substrate level phosphosphorylation), compared to the oxidative phosphorylation.

• Generates critical intermediates

Summary of TCA

• Generates critical intermediates

• Generates oxidized coenzymes (NADH, FADH2)

• Release carbon dioxide (reduces size of molecule)

Summary of ETS (oxidative phosphorylation)

• Accept electrons from oxidized coenzymes• Electron carriers transfer electrons to other

carriers.• Transfer H ions to one side of cytoplasmic

membrane (a gradient is formed)• H ions move back into cytoplasm by way of the

ATPase. Thus, ATP is generated in large amounts.

Alternate Glycolytic Pathway

• To supply coenzymes, critical intermediates, etc., during times of adaptation, absence of EM; other pathways are needed.

• Entner-Doudoroff pathway - aerobic bacteria (lack an EM enzyme), certain Archaea

• Less ATP generated• Generates NADPH, rather than NADH

Alternate Glycolytic Pathway

• Modified ED pathway

• Partially nonphosphorylated

• Some Archaea (Halo, Thermo), Eubacteria

• Less to no net production of ATP, compared to EM.

Alternate to glycolysis

• Methylglyoxal pathway

• Eubacteria - during low phosphate concentrations.

• Less ATP generated, compared to EM.

Pentose Phosphate Pathway

• Directly linked to EM or glycolysis

• Major role is to generate ribose for the biosynthesis (anabolism) of DNA, RNA, ATP NAD, NADP.

• Normal process (operates in conjunction with EM)

Glycolysis supplies energy for anabolism

Glucose

Pyruvic acid

TCA Cycle

NADH

NADH

Electron transport chain

(chemiosmosis)

H2OOrganic products

Respiration Fermentation

ATP

ATP

ATP

ATP

CO2

Metabolism

Catabolism

Energy (ATP)Small molecules (precursors)

Anabolism

Large molecules

Review Metabolism

• Shared with both respiration and fermentation

• Three phases of glycolytic pathway 1.) glycolysis 2.) TCA 3.) electron transport chain (oxidative phosphorylation)

• Three events during catabolism 1.)electron flow 2.)carbon flow 3.)energy production

Review continued

• 1.) Redox reactions• Depends on reduction potential, positive

value- more likely to accept electron.• Participating molecules ex. NAD, NADH

(electron donors or acceptors)• 2.) 6C molecule to two 3C molecules• C molecules (intermediates) enter

biosynthesis or is released as CO2

Review continued

• 3.) Three forms 1.) substrate level phosphorylation 2.) oxidative phosphorylation 3.) photophosphorylation

• Alternate forms of the glycolytic pathway exist in order to supply coenzymes, ATP, etc.

Fermentation• Variety of products are synthsized.• Use products to identify specific microoganim.• Ex. Lactic acid, Ethanolic, Propionic Acid, Mixed

Acid, Butanediol, Butyric acid, Amino acid, Acetic to methane

• Electron donor (substrate) and acceptor (product) are internal of the cell, thus less energy generated.

Mixed acid fermentation

• Methyl Red test - pH based test for acid production.

• Clinical labs use it to identify E. coli, urinary tract infections, etc.

• NADH is reoxidized to NAD

Butanediol fermentation

• Enterobacter, Serratia, Klebsiella-associated with opportunistic infections.

• Voges-Proskauer test - detects an intermediate metabolite.

• Used with MR test ex. VP-MR test

• Testing water supplies

• E.coli VP(-)MR(+), EnterbacterVP(+)MR(-)

Photoautotrophy• Absorption of light energy

• Oxygenic photosynthesis- algae, cyanobacteria, release oxygen, two photosystems exist

• Anoxygenic photosynthesis-Green and purple bacteria, no O is released, one photosystem