Bacterial MetabolismBacterial Metabolism

IntroductionEnzymes

Energy ProductionBacterial Catabolism

Bacterial Metabolism Bacterial Metabolism

Introduction– Metabolism - sum of all chemical

reactions in cell– Anabolism - reactions that synthesize

or “build up” e.g. protein synthesis– Catabolism - reactions that digest or

“break down” e.g. starch to glucose

Bacterial MetabolismBacterial Metabolism

Enzyme Introduction Enzyme Components Enzyme Mechanism Factors Influencing Enzymes

Bacterial MetabolismBacterial Metabolism

Enzyme Introduction– Enzymes are biological catalysts– Catalysts are agents which speed up

a reaction – Enzymes are very specific– Enzymes are typically proteins– Catalysts work by lowering the

activation energy of a reaction

Bacterial MetabolismBacterial Metabolism

Enzymes work to lower activation energy

Bacterial MetabolismBacterial Metabolism

Enzyme Components– Cofactor - nonprotein component that

is part of enzyme, e.g. Fe, NAD+, biotin

– Apoenzyme - protein portion of enzyme

– Holoenzyme - Cofactor plus apoenzyme

Bacterial MetabolismBacterial Metabolism

How enzymes speed up reactions– Proximity– Orientation– Induced fit– Reactive groups– Cofactors

Bacterial MetabolismBacterial Metabolism

Enzyme Mechanism– Substrate binds to active site; lock &

key specificity; induced fit– Formation of enzyme-substrate

complex– Catalytic activity; localized acid or

base or induced fit

Bacterial MetabolismBacterial Metabolism

Bacterial MetabolismBacterial Metabolism

Factors Influencing Enzymes– Temperature– pH– Salt concentration– Inhibitors

»Competitive (active site)»Non - Competitive (allosteric)

– Feedback Inhibition

Bacterial MetabolismBacterial Metabolism

Energy Production– Oxidation / Reduction reactions– Role of ATP– Phosphorylation

»Substrate»Oxidative»Photo-

Bacterial MetabolismBacterial Metabolism

Oxidation / Reduction– Oxidation - loss of electrons– Reduction - gain of electrons– Redox reactions always coupled– Oxidation of reduced carbon tends to

be energetically favorable

Bacterial MetabolismBacterial Metabolism

Carbon Oxidation/Reduction– Carbon Dioxide CO2 (+4)

– Acid (Formic Acid HCO2) (+2)

– Aldehyde (Formaldehyde - H2CO) ( 0 )

– Alcohol (Methanol - H3COH) (-2)

– Methane CH4 (-4)

Bacterial MetabolismBacterial Metabolism

Oxidation States– Alcohols– Fats– Organic Acids (acetic acid)– Glucose

Bacterial MetabolismBacterial Metabolism

Role of ATP– ATP ADP + Pi

– Energy intermediate or “currency”– Hydrolysis of ATP “coupled” to

energetically unfavorable reactions

Bacterial MetabolismBacterial Metabolism

Bacterial MetabolismBacterial Metabolism

Glucose + Pi Glucose-6-PO4 + H2O

ΔG = +13.8 kJ/mol, Keq = 5 x 10-3 ATP + H20 ADP + Pi

ΔG = -30.5 kJ/mol, Keq = 4 x 105 Glucose + ATP Glucose-6-PO4 +

ADP ΔG = (-30.5 kJ/mol) + (+13.8 kJ/mol)

= -16.7 kJ/mol

Bacterial MetabolismBacterial Metabolism

Phosphorylation– Substrate - direct transfer of phosphate

from an organic molecule to ADP– Oxidative - ATP generated via

chemiosmosis (“proton pump”) and ATP synthase

– Photo - light energy from photosynthesis, a modification of chemiosmosis

Bacterial MetabolismBacterial Metabolism

Bacterial Catabolism– Carbohydrate catabolism has two

functions:»energy production and/or storage»generation of chemical intermediates

– Cellular respiration and fermentation– Includes three processes:

»Glycolysis»Kreb’s or Tricarboxylic Acid (TCA) cycle»Electron transport /oxidative phosphorylation