final cellular energetics pt 2 Flashcards
how does photosynthesis generate chemical energy and reducing power
photosynthesis uses light energy to generate ATP and NADPH to allow CO2 to be “fixed” into organic molecules
are catabolic and anabolic pathways reverses or opposites of each other
opposites
what is photosynthesis
the synthesis of simple sugars from CO2 and H2O using energy from light
what are the two stages that photosynthesis occur in
light and dark reactions (in chloroplasts)
what do light reactions do
they harness light energy to generate ATP and NADPH; occurs in thylakoid membrane
what do dark reactions do
use ATP and NADPH to “fix” CO2 into organic compounds; occurs in stroma
what are the three chloroplast membranes
outer membrane, inner membrane, thylakoid membrane
what is the thylakoid membrane organized into
stacks called granum
what is the difference between light and dark reactions
light reactions are dependent on light, whereas dark reactions aren’t
what is the difference between NADPH and NADH
they’re energetically similar but NADPH is used for anabolic reactions and NADH is used for catabolic reactions
what are futile cycles and why don’t we want them
cells do an anabolic reaction, then a catabolic reaction on same set of molecules where then you just are building up and burning down, wasting energy - this happens if anabolic and catabolic cycles aren’t separated
how do light reactions work with dark reactions
take ATP and NADPH that were generated in light reactions and use them to fix CO2 from atmosphere to make 3-carbon sugars
what are photosystems
light is harvested by these two multi-protein complexes
what are the two photosystem reactions
electrons are transferred from ETC that pumps protons, which delivers electrons to NADP to make NADPH
what do proton pumps do in light reactions
they make proton gradients which are used in a pathway to generate ATP
what is used in the carbon-fixation cycle
ATP and NADPH are used when CO2 is reduced to generate carbohydrate molecules
what is the order of the photosystems
photosystem 2 is first, photosystem 1 is second
how do the two photosystems work
- photosystem II uses light energy to “split” 2 water molecules into 4 H+ and O2 and excite 4 electrons
- excited electrons from photosystem II pass through an electron transport chain to generate a proton gradient (just like in mitochondria), but the protons are pumped into the thylakoid space
- the proton gradient is used to generate ATP, required in the dark reactions
what is the final electron acceptor of light reactions
Photosystem I, which excites the electrons and passes them to NADP+ to generate NADPH, also required in dark reactions
what are some similarities between mitochondrial respiration and photosynthesis
both use electron transport chains to generate proton gradients, which generate ATP by chemiosmosis
what are some differences between mitochondrial respiration and photosynthesis (where electrons come from)
- in photosynthesis, they come from water
- in mitochondrial respiration, they come from catabolic reactions like glycolysis and krebs cycle
what are some differences between mitochondrial respiration and photosynthesis (final electron acceptor)
- final electron acceptor for the etc in mitochondria in O2 to generate water
- for proton pumping etc in chloroplast in photosystem I itself
what are some differences between mitochondrial respiration and photosynthesis (form of NAD)
mitochondrial respiration uses NADH, photosynthesis uses NADPH
what are some differences between mitochondrial respiration and photosynthesis (amount of proton pumping machines)
in mitochondrial ETC, 3
in photosynthesis, 1
what are some differences between mitochondrial respiration and photosynthesis (where energy comes from)
- energy for ATP generation and for reducing NADP to NADPH and generating proton gradient in photosynthesis comes from light
- in mitochondrial metabolism and glycolysis, the energy to reduce NAD and to generate ATP comes form oxidation of organic molecules
when do dark reactions occur
in the calvin cycle - starts with the addition of 3 CO2 to 3 molecules of ribulose 1,5-biphosphate
what happens in the calvin cycle
- take CO2 and attach it to 5-carbon molecule to generate 6-carbon intermediate
- catalyzed by RuBisCO, the most abundant protein on earth
- intermediate reacts to form 2 molecules of 3-phophoglycerate
what does the calvin cycle begin and end with
- calvin cycle makes glyceraldehyde 3-phosphate?
- ends and starts with some molecule
