BIS206 -Biostructures, energetics and synthesis Flashcards
If energy is conserved, why does it need to be resupplied?
-order of energy in system changes -entropy always increases
-energy is transferred into heat, which is irreversible
-life requires negative entropy
-to achieve -ve entropy, it must be coupled to a process of +ve entropy (breakdown of ATP)
What are the key principles of chemiosmotic theory?
-metabolic rxns gens electrochem grad
-ETCs, bacteriohodpsin and ATP synthase all catalyse H+ movement
-a topologically closed membrane is required for coupling
-uncouplers also de-energise membrane
-membr can be energised by imposing an artificial pH/electrochem grad
-metabolite accumulation is coupled to H+ movement
What it the chemiosmotic theory?
movement of ions across a membrane due to pmf
-coupled to rxns like ATP synthesis
What are uncouplers?
molecules which facilitates the diffusion of H+ across a normally impermeable membrane
-removes pmf
What is the evidence for the chemiosmotic theory?
-acid-bath experiment
-use of uncouplers to abolish H+ gradient also abolishes ATP synthesis, proving ETC and ATP synth are coupled
-combination/reconstruction of chemiosmotic components still allows coupling of pmf and ATP synth
How did Jagendorf’s acid bath experiment provide evidence for chemiosmotic theory?
acid bath could generate ATP without light-driven e- transfer
What was done in Jagendorf’s acid bath experiment?
-isolated chloroplasts were isolated at pH4 in the dark with weak acid (chloro and surroundings acidic)
-alkali (buffer), ADP and Pi added v quickly to create a momentary pH gradient
-observe ATP synthesis
How does using an uncoupler to abolish H+ gradient provide evidence for chemiosmotic theory?
shows a H+ gradient is needed to generate ATP
-ATP synthesis didn’t happen w/o a H+ gradient
How does combining chemiosmotic components provide evidence for chemiosmotictheory?
when reconstructed in lipid vesicles (liposomes) with ATP synthase (from beef mito), light-driven H+ pump (bacteriohodopsin) could drive ATP synthesis
What is proton motor force central to within a cell?
-e- transport
-ATP synthesis/hydrolysis
-metabolism
-transportation of metabolites
-movement (flagella)
-transhydrogenase
What are redox potentials like in respiration?
e- transferred down redox pot gradient
-ve ΔG released powers Δp formation for ATP synth
What are redox potentials like in photosynthesis?
e- transferred down redox pot gradient in each PS
uphill steps powered by light
-ve ΔG released powers Δp formation for ATP synth
How did the introduction of photosynthesis alter Earth?
-oxygen photosynth by cyanobact started to increase O2 conc in atmosphere
-as aerobic resp became more widespread and complex multicellular life developed, O2 conc cont to increase
-with the development of plants, the ozone layer was formed
-evolution of lignin decreased the O2 conc (as fungi and bacteria took longer to break down lignin; trees became stronger and taller)
What is the structure of chlorophyll?
-tetrapyrrole ring containing a Mg2+ ion
-conjugated 𝜋 e- system in pyrrole ring (responsible for light absorption)
-hydrophobic phytyl tail (branched hydrocarbon chain with no double bonds)
How are energetically unfavourable (+ve ΔG) reactions driven in photosynthesis?
light energy
-allows e- to be transferred from donor with +ve redox pot to acceptor with more -ve redox pot
