Metabolism

What is necessary for life?

• Water• Hydrogen• Oxygen– Can be toxic to some organisms unless in non-

reactive form (H2O)

• Phosphorous• Nitrogen• Carbon Source

Carbon Sources

• Organic and inorganic sources– Glucose– CO2

• Autotrophs: make their own food

• Heterotrophs: get food from others

Carbon Sources

• Photoautotrophs - CO2

Cyanobacteria Stromatolites

Carbon Sources

• Photoautotrophs - CO2

• Chemoheterotrophs - sugars (glucose usually)

Streptococcus pyogenes on blood agar

Carbon Sources

• Photoautotrophs - CO2

• Chemoheterotrophs - sugars• Chemoautotrophs - CO2

Carbon Sources• Photoautotrophs - CO2

• Chemoheterotrophs - sugars• Chemoautotrophs - CO2

• Photoheterotrophs - organic acids

Carbon Sources

• Photoautotrophs - CO2

• Chemoheterotrophs - sugars• Chemoautotrophs - CO2

• Photoheterotrophs - organic acids

Predatory bacteria

• Some bacteria feed on other microbes

• What is it?• Bdellovibrio

bacteriovorus

Metabolism

• How cells acquire and use energy• Anabolism• Catabolism

Usable Energy (E) for Cells

• ALL living things use ATP

• Energy transferred to drive chemical reactions

What do cells do with ATP?

Enzymes catalyzechemical reactions

• Characteristics• Nomenclature

Enzymes often act inmetabolic pathways

• Initial substrate• Intermediates• Final end

product

Anabolism

• Building molecules & parts from smaller molecules & parts

• What do you think of when you hear “anabolic?”

• Cell growth is anabolic process

Cell Growth

OXYGENOxygen can be helpful or harmful – depends on the

species!

TemperatureMicrobes have narrow range in which they thrive

Photosynthesis is a process to acquire chemical energy

• Necessity of pigment• Photosystems• Energy-fixing reactions• Carbon-fixing reactions

(Energy Fixing)

(Carbon Fixing)

Photosynthesis

• What goes in?

• What comes out?

• Convert light or chemical energy into organic compounds used by all other living things!

Photoautotrophs & Chemoautotrophs

Catabolism

• Getting energy out by breaking chemical bonds

• Burning wood is catabolic• Breaking bonds in glucose is catabolic

Glucose contains stored energy that can be extracted

• Energy from breaking C-C bond is transferred to produce ATP from ADP

Cellular respiration is a series of catabolic pathways for the production

of ATP

• Aerobic respiration• Anaerobic respiration

Glycolysis is the first stage of energy extraction

• Pathway same in prok & euk (all living cells)• Reactions of glycolysis: gain…• ATP • NADH

Glycolysis

• What goes in?

• What comes out?

The Krebs cycle extractsmore energy from pyruvate

• Pyruvic acid preparation• From Krebs cycle:• ATP• NADH and FADH2

Krebs Cycle

• What goes in?

• What comes out?

Electron Transport Chain -

• Important components – NADH and FADH2 electron donors– Coenzyme Q– Cytochromes (C1, C, A3) electron acceptor/donor

to oxygen (or S)– Oxygen (or S)- accepts electrons & hydrogen to

become H2O

Same in humans! rxns take place in mito. membraneendosymbiosis

Electron Transport System

• What goes in?

• What comes out?

TCA

38 ATP

• One molecule of glucose yields 38 ATP

What if there is no oxygen?

• Some can’t have any oxygen– use another electron acceptor (ie sulfur)

• Some use fermentation instead of respiration– recycles NAD for glycolysis– gets rid of harmful pyruvate

Fermentation

• Energetically inefficient– Net 2 ATP per glucose from glycolysis – Compared to aerobic gain?

2 ATP

• One molecule of glucose yields 2 ATP if goes thru fermentation

• In general, anaerobic organisms grow very slowly…