Mitochondria and chloroplasts Flashcards
anabolic reaction
energy requiring
catabolic reaction
energy yielding
F0 component of ATP synthase
integral membrane
Forms a channel that allows protons (H⁺) to pass through the membrane. This component harnesses the energy from the proton gradient to drive the rotational motion necessary for ATP synthesis
F1 component of ATP synthase
peripheral, on cytoplasmic side of membrane
catalytic sites for ADP+Pi–>ATP
mechanism of ATP production by ATP synthase in terms of energy transfers
proton gradient = stored energy
as protons floe through F0, energy converted to mechanical energy to move the stalk, which mechanically deforms the F1 subunits (alpha and beta). this conformational energy is converted to chemical bond energy
components of proton gradient
membrane potential (difference in voltage)
difference in proton concentration (change in pH)
conformational changes proton pumps
initial conformation accepts an electron and a proton. neutralisation causes conformational change=proton facing other side of membrane. release of proton=revert to original conformation
3 complexes in mitochondrial inner membrane that pump protons
NADH dehydrogenase
cytochrome bc1 complex
cytochrome oxidase complex
cytochrome oxidase complex
stores oxygen that combines with the electrons to form water
what do mobile electron carriers do
transfer electrons between proton pumping complexes
ubiquinone
lipid-like
carries electrons from NADH dehydrogenase to the cytochrome bc1 complex
cytochrome c
carries electrons from cytochrome bc1 complex to cytochrome oxidase complex
direction of proton transfer for mitochondria
protons are pumped into intermembrane space from matrix via the pumps
establishes proton gradient
protons pass to the matrix via ATP synthase
high electron transfer potential
donates electrons
-ve
strong reducing agent
eg NADH
why is H2O a poor electron donor
low electron transfer potential
+ve
how does redox potential change along the ETC
redox potential/electron affinity increases along the chain. the free energy of the electrons is proportional to redox potential
how do the pumps have different redox potentials
metal centres
how many NADH are generated by citric acid cycle
3
why do NADH produced in cytosol in glycolysis yield less ATP than in matrix
Transporting these NADH into mitochondria requires energy so the net ATP yield is lower from these NADH molecules
cyanide and carbon monoxide
inhibit cytochrome oxidase
mitochondrial uncoupler
protons flow through mitochondrial membrane but not through ATP synthase
eg DNP
dangerous
where are the photosystems situated in a chloroplast
thylakoid membranes
why is light energy needed
electrons for the ETC come from water which is a poor electron donor so a lot of energy is needed to remove them
how is the proton gradient generated in chloroplasts
electron transfer coupled to proton pumping (as in mitochondria)
protons released from photolysis
light harvesting complexes
channel the energy from the absorption of sunlight into electrons into a special pair of chlorophyll molecules
photosystems
large multi subunit protein complexes
contain chlorophyll
composed of antenna complex and a reaction centre
antenna complex
collects the energy from sunlight and channels the energy (energy transfers) to a pair of electrons in the reaction centre.
plastoquinone
electron transfer molecule in chloroplasts
transfer of electrons in chloroplasts
photosystem II > plastaquinone > cytochrome b6f complex (pumps protons into thylakoid lumen) > plastocynain > photosystem I (also has antenna complex and reaction centre, absorbs light, excites electrons to higher energy level again) > ferredoxin > NADPH in NADP reductase
plastocyanin
small copper containing protein
ferredoxin
small protein containing an iron-sulfur centre
for every 3 carbon sugar produced in calvin cycle, how many ATP and NADPH are needed
9
6
rubisco
catalyses first reaction in carbon fixation
fixes carbon fromm CO2 onto a 5 carbon compound called ribulose bisphosphate to form a 6C compound
what occurs in the stroma
ATP synthesis
NADPH synthesis
carbon fixation
