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Ch. 9: Cellular Respiration and Fermentation, Ch. 10: Photosynthesis -…

- - - - Comparison of Fermentation, Anaerobic and Aerobic Respiration
        Similarities:
        ~All use glycolysis
        ~NAD+ is oxidizing agent that accepts electrons during glycolysis.
        Differences:
        ~pyruvate or acetaldehyde are final electron acceptors in fermentation.
        ~electrons transported to ETC during cellular respiration.
        ~fermentation produces 2 ATP bye substrate-level phosphorylation.
        ~cellular respiration harvest much more ATP by oxidative phosphorylation. ~32 ATP
      - Obligate Anaerobes- cannot survive with O2.
        ~carry out fermentation or anaerobic respiration.
        Facultative Anaerobes- can survive with or without O2.
        ~use fermentation of cellular respiration.
        ~yeast and many bacteria
    - - ~Cellular Respiration includes both aerobic and anerobic BUT often referred to as aerobic respiration.
        Carbohydrates, fats and proteins can all be consumed during cellular respiration.
        ~proteins digested to amino acids and their amino groups are removed by a process called deamination
        ~fats digested to glycerol (used in glycolysis) and fatty acids broken down by beta oxidation- yields acetyl Co-A, NADH and FADH2.
      - C6H2O6 + 6O2 :arrow_right: 6CO2 + 6H2O + Energy (ATP + Heat)
  - - - ~During Cellular respiration- organic molecules are oxidized (lose electrons) and O2 is reduced (gain electrons).
        Each electron travels with one proton- or as a hydrogen atom H
        Hydrogen ion (H+) - represents ONE proton or a hydrogen atom that has lost its electron
        Organic molecules with abundance of HYDROGEN are excellent sources of high-energy electrons
      - Electron acceptors
        
        ~During cellular respiration, there are coenzymes that function as electron carriers- carry H+ to a specific site.
        Electron carriers/ Oxidizing agents:
        NAD+ (nicotinamide adenine dinucleotide) - reduces (gains electron) to NADH.
        ~ carries 2 e- and 1 p+ to Complex 1 of ETC- other proton is released as a hydrogen ion
        FAD (flavin adenine dinucleotide) - reduces (gains electrons) to FADH2
        ~ carries 2 e- and 2 p+ to Complex 2 of ETC
- - - - Electron Transport Chain (ETC)- Complex of four proteins and cytochromes within the inner membrane phospholipid bilayer of the mitochondria.
        All proteins within the complex have cofactor carriers that pass electrons along their electronegative gradient (down the ETC). From complex 1 to complex 4.
        ~the electron carriers alternate between reduced and oxidized sates as the accept and donate electrons.
        ~NADH donates its electrons to Complex 1-- oxidizes back to NAD+.
        ~FADH2 donates its electrons to Complex 2-- oxidizes back to FAD.
        cytochrome Q (ubiquinone) and C- proteins containing iron that help move electron along the ETC.
        Complex 1, 3, and 4 are transmembrane carrier proteins that serve as proton pumps. Pump H+ from the matrix into the intermembrane space. This is crucial for Chemiosmosis.
        As electrons get transferred from one complex to the next, free energy is released.
        That free energy is then used by the proton pumps to pump H+ against its concentration gradient- energy coupling
        Complex 4- the end of the electron chain.
        Terminal Electron Acceptor- 1/2 O2 molecule picks up 2 electrons from ETC and 2 protons (H+) from matrix to form H2O.
    - - [H+] is high in intermembrane space and low in the matrix.
        ~H+ moves down its [] gradient.
        ATP Synthase- transmembrane carrier protein complex that synthesizes ATP.
        ~H+ passes through the rotor of ATP synthase.
        ~The gradient force from H+ entering the rotor -proton-motive force catalyzes phosphorylation of ADP to ATP.
- - - - absorption spectrum of chlorophyll a indicates that violet-blue and red light work best for photosynthesis.
        action spectrum- a profile of the relative effectiveness of different wavelengths.
        ~confirms effectiveness of violet-blue and red light for photosynthesis.
      - ~Chlorophyll a and b have a magnesium atom at center.
        porphyrin ring- light absorbing head of molecule with Mg center.
        ~hydrocarbon tail that interacts with hydrophobic regions of proteins in the thylakoid membrane.
- - - - When a pigment molecule (such as chlorophyll a, b or carotenoids) absorb light, one of its electrons goes to an excited state.- becomes unstable
        As the e- collapses back to ground state energy, it releases trapped energy.
    - - Photosystem
        
        Photosystem- consist of a reaction-center complex surrounded by light-harvesting complexes.
        ~located in the thylakoid membrane.
        Reaction-center complex- association of proteins holding a special pair of chlorophyll a molecules and a primary electron acceptor.
        Primary electron acceptor- accepts excited electrons an is REDUCED (gains e-) as a result.
        Light-harvesting complex- various pigment molecules bound to proteins.
        TWO PHOTSYSTEMS: Named in order they were found
        Photosystem II (PS II)- called P680 because its reaction-center chlorophyll a is best at absorbing light wavelengths of 680 nm.
        ~FIRST photosystem on photosynthesis
        Photosystem I (PSI)- called P700 because its chlorophyll a is best at absorbing light wavelengths of 700 nm.
        
        Light-harvesting complexes are hit with light energy :arrow_right: transfer the energy from the photons along the pigment molecules to the chlorophyll a pair in the reaction-center complex :arrow_right: chlorphyll a pair transfer the excited electron to the primary electron acceptor in the reaction-center complex
      - Electron Flow
        SECOND STEP IN LDR
        
        Two possible routes for electron flow during light dependent reactions:
        Linear electron flow
        ~Primary pathway
        ~Involves Both photosystems
        ~Produces ATP, NADPH and O2 using light energy
        Cyclic
        ~electrons cycle back to cytochrome complex after Fd instead of being transferred to NADP+
        ~Uses only PS I
        ~Produces ATP, but no NADPH or O2
        ~produces quite a bit of ATP
        
        Linear Electron Flow
        
        Cyclic Electron Flow
        
        Linear Electron Flow
        Photon hits pigment in light-harvesting complex of PS II and its energy is passed to P680 :arrow_right: excited electron from P680 is transferred to the primary electron acceptor (oxidized P680+) :arrow_right: enzyme catalyzes the split of H2O into two electrons (transferred to P680+ pair, reduces to P680). two H+ (released into the thylakoid space) and an oxygen atom (combines with another oxygen atom from H2O split to form O2) :arrow_right: electrons are passed (redox reactions) from the primary electron acceptor of PS II to Pq (Plastoquinone) to cytochrome complex to Pc (Plastocyanin) to PS I (energy released by electron transfer is used to pump H+ into the thylakoid space to create a proton gradient along the membrane) :arrow_right: Potential energy in the proton gradient drives the production of ATP by chemiosmosis using ATP Synthase :arrow_right: PS I, light energy excited P700, and transfers electron to its primary electron acceptor (P700+ accepts electron from ETC) :arrow_right: Electrons passed from primary electron acceptor to second ETC to protein Fd (Ferredoxin) :arrow_right: NADP+ Reductase catalyzes the transfer of electrons from Fd to NADP+ (two electrons reduce NADP+ to NADPH) :arrow_right: NADPH and ATP head to the Calvin Cycle
        ATP and NADPH are produced on the stroma side of the thylakoid membrane
        
        Cyclic Electron Flow
        Photoexcited electrons cycle back from Fd to cytochrome complex :arrow_right: to Pc :arrow_right: to PS I P700
        ~several photosynthetic bacteria have only a single photosystem- cyclic electron flow is the only means of generating ATP during photosynthesis.
        ~Cyclic electron flow may have photoprotective *capability- can grow well in low light.
  - - - Rubisco enzyme combines ONE CO2 molecule with RuBP :arrow_right: splits into two 3-PGA
    - - Each 3-PGA molecule is phosphorylated by 6 ATP and reduced by 6 NADPH to produce ONE G3P
        ~3 turns of the Calvin Cycle = 1 G3P
        ~Two G3P = 1 glucose molecule
        ~every 3 CO2 molecules to enter cycle- 6 G3P are formed.
        one in six of the G3P formed is used to produce glucose
        ~other 5 are used to regenerate RuBP
    - - Five G3P are phosphorylated by 3 ATP to facilitate the regeneration of 3 RuBP