Photosynthesis Flashcards
What is the Light Reaction in photosynthesis?
energy from light is used to create unstorable chemical energy
What is the calvin cycle?
AKA stoma reactions, dark reactions
chemical energy from the light reactions is used to create stable, storable chemical energy
What is the structure of the Cholroplast?
has many membrane-enclosed compartments inside it that form into sacks
What is in the sacs?
the sacs have aqueous interiors, the membrane surrounding them and the squeous solution around the sacks add up to three sites of important processes in photosynthesis
what happens in the thylakoid membrane?
The thylakoid membranes of a chloroplast is an internal system of interconnected membranes, that carry out the light reactions of photosynthesis.
what happens in the thylakoid space?
The thylakoid space is the space on the inside of the thylakoid. A thylakoid is membrane-bound disc in the chloroplast of plant cells. The membrane of the thylakoid contains enzymes necessary for the light dependent reactions of photosynthesis.
what is the stroma?
colorless fluid surrounding the grana within the chloroplast. Within the stroma are grana, stacks of thylakoid, the sub-organelles, the daughter cells, where photosynthesis is commenced before the chemical changes are completed in the stroma.
Chloroplast pigment:
what is chlorophylls a and b?
land plants have cholrophyll a and b
different a have methyl group
Chloroplast pigment:
what are the three?
chlorophylls a and b
carotenoids
phycobilins
carotenoids are responsible for what?
pigments responsible for bright red, yellow and orange hues in many fruits and vegetables
phycobilins are responsible for what?
Any of a class of water-soluble, mostly red, orange, and blue pigments found in cyanobacteria and red algae. Phycobilins absorb the blue and blue-green frequencies of light which penetrate deep water, and allow red algae to carry on photosynthesis at greater depths than other organisms.
Light spectra:
visible light is what? what is its range?
electromagnetic radiation in the wavelength rage of 380-750nm
if a pigment is dissolved in a specific solvent it will have a what?
characteristic absorption spectrum and that spectrum will be unique to that molecule (like a fingerprint)
What is a photosystem?
is an assembly of several light harvesting complexes that gather sunlight and pass the energy to a reaction center complex
What are the pigments in the photosystem?
chlorophyll a and b
carotenoids
pigments in the light-harvesting complex do what?
absorb light and transfer the energy to the reaction center chlorophyll a
What happens to the reaction center (chlorophyll a) after absorbing the energy from the light harvesting complex?
the molecules are oxidized
the light reaction:
what are the two kinds of electron flow that occur in this reaction?
non-cyclic and cyclic noth of which lead to the synthesis of ATP driven by light (photophosphorylation)
what happens in non-cyclic photophosphorylation?
the Z-scheme
electrons move from a weak electron doner (H20) to a weak electron acceptor (NADP+). the movement of electrons also drives the formation of an H+ gradient, which is used to power ATP synthesis
What is the problem posed by the Z-scheme?
it makes equal amounts of ATP and NADPH. but the subsequent Calvin cycle reaction needs more ATP than NADPH (3:2 ratio). the solution to the problem is cyclic photophosphorylation. which makes ATP but no NADPH
How is the problem of the Z-scheme solved?
the electrons cycle through photosystem 1 only
a given photosystem will flip back and forth from cyclic and non-cyclic electron flow depending on the availability of NAHP+
what form of electron flow would a photo system use if there is low NADP+?
cyclic electron flow
what form of electron flow would a photo system use if there is high NADP+?
non cyclic electron flow
The Calvin Cycle:
What does the Calvin cycle make?
it makes carbohydrate by fixing (reducing) CO2
The Calvin Cycle:
how was this cycle discoved?
by Melvin Calvin who used radioactive carbon (14C) as a tracer
The Calvin Cycle:
what is the first enzyme?
runisco (RuBP)
The Calvin Cycle:
what is the first reaction of the calvin cycle?
RuBP (5C) + CO2 (1C) –> 2x3-phosphoglycerate (2x3c)
What is the net gain of the calvin cycle?
3 turns (three carbons fed in) –> 1 glyceraldehyde-3-phosphate
What is glyceraldehyde-3-phosphate used for? (5)
sugar, starch, cellulose
AA, protein
Nucleic acid
lipid
secondary metabolites