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Metabolism
- “sum of all chemical reactions within a living organism” (Tortora)
- Ability to convert energy from one form to another
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Laws of Thermodynamics
- 1. Energy is neither created or destroyed-only converted from one form to another
- 2. Energy conversion results in an increase in entropy (disorder) usually in form of heat.
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Microbial Diversity: Metabolic Diversity
- Bacteria have many of the same energy-generating processes as eukaryotes
- But also have many unique processes not seen in eukaryotes
- Including:
- unique fermentations
- anoxic photosynthesis
- lithotrophy (using inorganic substances for energy)
- methanogenesis
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Two kinds of reactions in cells
- Anabolic (endergonic)
- Catabolic (exergonic)
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ATP
- All cells are powered by ATP
- ATP hydrolysis is exergonic
- Exergonic reactions provide energy to power endergonic reactions – ATP is the “go-between”
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ATP Synthesis
- Substrate-level phosphorylation
- Oxidative Phosphorylation
Hydrogen are charged so they cant just get through the lipid bilayer. Water is everywhere and it loves the hydrogen. Animals that hibernate and babies have a pore that lets the hydrogen come back in to make heat instead of ATP. Each protein wants the electron more and more until it gets to oxygen which is an electron hog. Hydrogen is not wanted so it puts it up and creates a gradient which is not stable. Its gets relieved by going through ATP synthase. It is like a water wheel.
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Collision Theory
- For reactions to take place, the molecules must collide:
- With enough velocity
- In correct orientation
- Reactions are also affected by concentration
- Low concentrations=few collisions
- High concentrations=more collisions
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Enzymes are Biological Catalysts
- Most are proteins
- Lower EA
- Speed up reactions
- High reaction rates
- Enzymes orient reactants
- Enzymes put reactants in the correct orientation
- Turnover
- Stabilize the transition state
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Enzymes
- Some require cofactors (vitamins or minerals)
- Affected by inhibitors (competitive, non-competitive)
- Affected by temperature, pH, antibiotics, other chemicals
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Facts about Enzymes
- Most are proteins
- Biological catalysts
- Lower EA
- Specific
- Bind Substrate in active site
- Not used up in the process
- Affected by pH, temperature, chemicals
- Feedback inhibition
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NADH is an electron carrier
- NAD+ is resonance stabilized
- NADH is less stable
- NADH acts as an e- and H+ shuttle
- The addition of one Hydrogen keeps the bonds in place. It makes the other bonds weaker. NAD+ is stronger. NADH is not as stable so it makes it reactive.
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Energy
- All organisms require energy to run their cellular processes
- Two ways to obtain energy:
- Phototrophs: energy from sunlight
- Chemotrophs: energy from molecules
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At the end of Glycolysis there are 2 possible routes to follow
- Acetyl CoA-Kreb Cycle
- or
- Pyruvic Acid
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Fermentation
- Releases energy from sugars or other organic molecules
- Does not require O2
- Does not require Kreb’s cycle
- Uses an organic molecule as the final e- acceptor
- Produces only small amounts of ATP
- Regenerates NAD+ or NADP+ so sugar metabolism can continue (glycolysis, ppp, E-D)
Fermentation uses an organic compound as the terminal electron acceptor
- Organism is Clostridium ends as Butyric Acid, Butanol or acetone.
- Starts out as Enterobacter end product formic acid
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Aerobic Respiration
- Final Electron Acceptor is Oxygen
- Substrate level and oxidative phosphorylation
- 36 ATP in Euk.
- 38 ATP in Prok.
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Anaerobic Respiration
- Final Electron Acceptor is usually an inorganic substance like nitrogen, sulfur
- Substrate level and oxidative phosphorylation
- Variable ATP fewer than 38 but more than 2
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Fermentation
- Anaerobic or aerobic
- An organic molecule is the final electron acceptor.
- Substrate level phosphorylation
- 2 ATP
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Photosynthesis
- Sunlight (kinetic) converted into chemical (potential) energy
- Cyanobacteria, algae
- Purple sulfur, green sulfur
- Purple nonsulfur
- Green nonsulfur
- Light energy converted to chemical energy
- Two reactions:
- Light
- Dark (Calvin Cycle)
- Cellular respiration starts with glucose (6 carbons) and yields 6CO2 +Water + ATP = exergonic rxn. 3 steps
- Photosynthesis starts with 6CO2 + water + sunlight yields glucose and CO2 = endergonic rxn. 2 steps (Light and dark)
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Chlorophyll
- Sunlight excites e- from Mg
- The e- passed down a series of acceptors
- NADP+ final electron acceptor
- More sunlight excites e- further
- H+ gradient produced
- Used to drive ATP synthesis
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