Bmsc 210 Mid1 p6

• • Glycolysis
• • Respiration and Electron Carriers
• • The Proton Motive Force
• • The Citric Acid Cycle
• • Catabolic Diversity

• substrate-level phosphorylation;
• -ATP directly synthesized from Energy-rich phosphate bonds in phosphorylated organic intermediates
• -Fermented substance is both an electron donor and an electron acceptor
• • Relatively little energy yield
• • Redox balance is achieved by production of fermentation products

• oxidative phosphorylation; ATP produced from proton motive force formed by transport of electrons
• • Exogenous electron acceptors are present to accept electrons generated from the oxidation ofelectron donors

• 
• a common pathway for catabolism of glucose
• – Anaerobic process
• – Fermentation: pyruvate is reduced by NADH to lactate to create 2NAD⁺
• • Some harnessed by humans for consumption

• first step in glycolosis
• enzyme: hexokinase
• couple reaction with ATP
• products:ADP+G6P
• ATP+Glucose->ADP+G6P

• – Oxidation using O₂ as the terminal electronacceptor
• – Higher ATP yield than fermentations
• • ATP produced at the expense of the protonmotive force, which is generated by electrontransport

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• – Membrane associated
• – Mediate transfer of electrons
• – Conserve some of the energy released during transfer and use it to synthesize ATP
• – Many oxidation–reduction enzymes are involved in electron transport (e.g., NADH dehydrogenases, flavoproteins, iron–sulfur proteins, cytochromes)

• chemo vs photo (energy)
• organo vs litho (whats being oxidized)
• hetero vs auto (carbon source)

pathways used for both catabalism and anabalism

• -proteins bound to inside surface of cytoplasmic membrane;
• -active site binds NADH and accepts 2 electrons and 2 protons that are passed to flavoproteins

contains flavin prosthetic group (e.g., FMN, FAD) that accepts 2 electrons and 2 protons but only donates the electrons to the next protein in the chain. Protons move to outside of membrane-pmf (Figure 4.15)

• – Proteins that contain heme prosthetic groups(Figure 4.16)
• – Accept and donate a single electron via the iron atom in heme

• – Contain clusters of iron and sulfur (Figure 4.17)
• • Example: ferredoxin
• – Reduction potentials vary depending on number and position of Fe and S atoms
• – Carry electrons in FeS prosthetic group

• – Hydrophobic non-protein-containing molecules that participate in electron transport (Figure 4.18)
• – Accept electrons and protons but pass along electrons only.Protons are moved outside the membrane-pmf

• • Electron transport system oriented in cytoplasmic membrane so that electrons are separated from protons (Figure 4.19)
• • Electron carriers arranged in membrane in order of their reduction potential
• • The final carrier in the chain donates the electrons to the terminal electron acceptor
• • During electron transfer, several protons are released on outside of the membrane
• – Protons originate from NADH and the dissociation of water
• • Results in generation of pH gradient and an electrochemical potential across the membrane (the proton motive force)

• negative
• alkaline

• positive
• acidic

• complex that converts proton motive force into ATP; two components(Figure 4.20)
• – F₁
• – F_o
• – Reversible; dissipates proton motive force

multiprotein extramembrane complex, faces cytoplasm converts adp and Pi to ATP

proton-conducting intramembrane channel

• reduction of inorganic carbon to organic compunds by living organisms
• -photosynthesis

• pathway through which pyruvate is completely oxidized to CO₂ (Figure 4.21a)
• -Function however is to create reducing power- NADH
• – Initial steps (glucose to pyruvate) same as glycolysis
• – Plays a key role in catabolism and biosynthesis

6 CO₂ molecules released and 8NADH and 2FADH 2GTP(ATP equivalent) generated

• 1st level: CO₂, pyruvate and acetyl phosphate
• 2nd level: CO_2, Ethanol, and Lactate

• precursors of several amino acids; OAA also converted to phosphoenolpyruvate, a precursor of glucose
• -product of citric acid cycle

• required for synthesis of cytochromes, chlorophyll, and other tetrapyrrole compounds
• -product of citric acid cycle

• necessary for fatty acid biosynthesis
• -product of citric acid cycle

• Ketoglutarate and oxalacetate (OAA):
• Succinyl-CoA
• Acetyl-CoA

• – Fermentation
• – Aerobic respiration
• – Anaerobic respiration
• – Chemolithotrophy
• – Phototrophy

• – The use of electron acceptors other thanoxygen
• • Examples include nitrate (NO3-), ferric iron(Fe3+), sulfate (SO42-), carbonate (CO32-),certain organic compounds
• – Less energy released compared to aerobicrespiration
• – Dependent on electron transport, generationof a proton motive force, and ATPase activity

• – Uses inorganic chemicals as electron donors. Less reduction power
• • Examples include hydrogen sulfide (H2S), hydrogen gas (H2), ferrous iron (Fe2+), ammonia (NH3)
• – Typically aerobic
• – Begins with oxidation of inorganic electron donor
• – Uses electron transport chain and proton motive force
• – Autotrophic; uses CO2 as carbon source

organisms that obtain energy from the oxidation of inorganiccompounds

are chemolithotrophs that require organic carbon as a carbon source

• • Many sources of reduced molecules exist inthe environment
• • The oxidation of different reduced compoundsyields varying amounts of energy

• • Ferrous iron (Fe2+) oxidized to ferric iron(Fe3+)
• • Ferric hydroxide precipitates in water
• • Many Fe oxidizers can grow at pH < 1 – Often associated with acidic pollution from coal mining activities (Figure 13.23)
• • Some anoxygenic phototrophs can oxidize Fe2+ anaerobically using Fe2+ as an electron donor for CO2 reduction
• • Ferrous iron oxidation begins with an outermembrane cytochrome c oxidizing Fe2+ to Fe3+, passing the electrons to rusticyanin in the periplasm (Figure 13.24)
• • Rusticyanin then reduces a cytochrome c in the inner membrane, and this subsequently reduces cytochrome a
• • Cytochrome a interacts with O₂ to form H₂O
• -electron reduces NAD⁺  to NADH
• • ATP is synthesized from ATPases in the membrane
• NADH+CO₂+ATP->organic material

• Autotrophy in Acidithiobacillus ferrooxidans is driven by the Calvin cycle

uses light as energy source

light-mediated ATPsynthesis

use ATP for assimilation of CO2 for biosynthesis

use ATP for assimilation of organic carbon for biosynthesis

• is the conversion of light energy tochemical energy
• – Carried out by phototrophs(Figure 13.1)
• – Most phototrophs are also autotrophs
• • Photosynthesis requires light-sensitive pigments called chlorophylls
• • Photoautotrophy requires ATP production and CO₂ reduction

• • Oxygenic phototrophs use light to generate ATPand NADPH
• • The two light reactions are called photosystem I and photosystem II
• • “Z scheme” of photosynthesis (Figure 13.18) – Photosystem II transfers energy to photosystem I
• • ATP can also be produced by cyclicphotophosphorylation

• -ATP can also be produced only using photosystem 1 by energizing electrons with photons and dropping down through a chain creating pmf.
• -electrons are energized again instead of being given to Nad

-electrons are boosted by photons and dropped twice creating proton motive force