inner and outer envelopes that regulate metabolite flux in and out of the chloroplast

Stroma: space between envelope and thylakoids that contains C3 photosynthetic enzymes

Stromules: tubules that connect stroma of chloroplasts and permit exchange of small metabolites

replicates independently of nucleus, with the number within a cell type remaining constant and with some coordination with the nucleus

contains gene expression machinery (DNA, RNA, Ribosomes 70S)

most proteins important from cytosol, whose genes are encoded in the nucleus

ctDNA replication and fission indpendent of nuclear DNA replication and cell division

Formation of light-absorbing pigments (chlorophylls, carotenoids)

Rapid membrane proliferation (stromal lamellae, grana stacks)

accumulation of protochlorophyllide (pale yellow-green pigment, precursor of chlorophyll)

each photon carries a discrete amount of energy that acts as a function of its wave properties (frequency and wavelength)

speed of light constant: 3 x 10^8 m s-1; related to wavelength and frequency

Photosynthetically active radiation: abbr = PAR, wavelengths = 400-700 nm

more light absorbed by equal concentration of chlorophyll in solution than by chloroplasts

light transmitted via intracellular spaces, cell walls, and central vacuole to cells below

reflects light within leaf, resulting in light scattering and a path of light 4x leaf thickness

modifications to reflect light such as hairs, salt glands, and epicuticular wax

chloroplasts align along cell surface parallel to plane of leaf lamina

PHOT activates protein kinase and induces a rapid change in cytoskeleton

in low light, chloroplasts align along cell surface parallel to plane of leaf lamina so they are perpendicular to incident light

in high light, chloroplasts align along sides of the cell and shade one another to reduce light absorption about 15%

leaf movement regulates light absorption, with maximum absorption occurring when lamina are perpendicular to incident light

maintains maximal light harvesting throughout day, maximizes photosynthesis when water loss is lower

accepts 2 e- from PQ, directing one to PSI and one to the Q-cycle

redox centers in cyt b6f complex include b-type cytochrome, c-type cytochromes, and Reiske Fe-S protein

small water soluble molecule in thylakoid lumen that carries one e- from cyt b6f complex to PSI after PSI loses e- following absorption of a photon

MEMORIZE PATHWAY ILLUSTRATION, STEPS, AND PARTS P73-98, MAKE UNIQUE WEB

some e- used to reduce thioredoxin to regulate various enzyme activities in chloroplast

some e- used to convert NO2 to NH4 for incorporation into organic molecules

process determined by Jagendorf experiment: generation of electrochemical gradient in the dark without PET activity

chlorophyll a/b antenna proteins are members of a large family of structurally related proteins

trimeric transmembrane complex, with each monomer containing three alpha helices spanning the thylakoid membrane and 14 chl a and chl b molecules plus four carotenoid molecules

spectroscopy measures absorbance of sample at selected wavelength

spectrofluorometry measures fluorescence of sample by excitation wavelength and emitter wavelength and is a more sensitive method than spectrophotometry

use spectroscopy to monitor redox state of electron donors/acceptors

was experimentally isolated first, hence its name, but occurs second in pathway

was isolated experimentally second but occurs first in pathway

Dissipation of electrochemical gradient occurs through ATP synthase

Change in pH is main component of change in proton motive force in chloroplasts

peripheral membrane protein complex on stromal side of thylakoid with several protein subunits and regulatory units

Paraquat binds to reducing side of PSI and prevents e- transfer to Fd

photooxidation occurs through highly reducing reactions leading to instability and generate reactive oxygen species

carotenoids vent excess energy, prevent singlet oxygen, and radiate heat

PSII easily damaged via photoinhibition, with D1 being the main target and needing to be resynthesized

sensible heat loss via conduction/convection of heat to cool air

evaporative heat loss (latent) via evaporative cooling and transpiration

in well-watered plants, increased transpiration = decreased Bowen ratio

on a still day, decreased sensible heat loss means decreased bowen ratio

may be negative--cotton leaves cooled below air temp by evaporation, resulting in sensible heat flow into leaf

MEMORIZE REGULATION AND SEPCIFIC ENZYMES, NOT MECHANISM

Variations: L2 in non-sulfer bacteria and dinoflagellates; some brown, red, and green algae encode both rbcL and rbcS

Rubisco is a dual-function enzyme: used in both C3 photosynthetic cycle and photorespiratory cycle

rubisco catalyzes CO2 fixation with product being 3-PGA in C3 photosynthetic pathway

carboxylation favored, but O2 competes and reduces net photosynthesis

NADP-GAPDH is an isozyme similar to glycolysis except for its cofactor

removes carboxyarabinitol-1-P (natural inhibitor that binds in dark and is removed in light)

Enzymes that require Mg2+ for catalysis more active at alkaline pH, including rubisco and others

thioredoxin coordinates PET activity with other pathways or processes

Thioredoxin reduces target enzyme by altering enzyme activyt or sensitivity to allosteric effectors

MEMORIZE, MEMORIZE, MEMORIZE FOUR ENZYMES REGULATED P150

the more light there is, the more reduced thioredoxin is present

increased oxidized thioredoxin results in oxidization of CP12 and creation of complexes that bind the enzymes PRK and G3PDH to inactivate them

increased reduced thioredoxin dissociates CP12 complex to allow PRK and G3PDH to become active

oxidative pentose phosphate pathway changes NADP+ to NADPH in chloroplast

thermal inhibition of photosynthesis impacts protein stability, membrane stability, and water relations

MEMORIZE P154 CHARACTERISTICS OF LIMITATIONS TO PHOTOSYNTHESIS RATE

sucrose and starch synthesis strongly inhibited by low temperature

carotenoid system dissipates excess light energy via conversion among epoxidation states

de-epoxidation occurs when xanthophylls transfer e- to H2O via ascorbate

transgenic plants without isoprene emission more heat sensitive

MEMORIZE REGULATION AND REDUCING AGENT FOR EACH

no taxonomic relationship between types of C4 photosynthesis; has arisen via convergent evolution 62 times

Permits reduced stomatal aperature, reducing H2O loss and permitting growth at higher temperatures

regulated by PEP carboxylase, which is activated by protein phosphorylation

regulated by pyruvate-Pi dikinase, which is controlled by adenylate energy charge

regulated by malate dehydrogenase, which is activated by thioredoxin system (light)

regulated by pyruvate-Pi dikinase, which is controlled by adenylate energy charge

regulated by PEP carboxylase, which is activated by protein phosphorylation

regulated by pyruvate-Pi dikinase, which is controlled by adenylate energy charge and whose regulation is mitigated by PEP transport

respiration increases with temperature, rather than decreasing like in C3 plants

C4 mechanism traps and recaptures respired CO2, so quantum yield is stable with increasing temperature

regulated by PEP carboxylase, which is activated by protein phosphorylation

In light, closed stomata prevent H2O loss and CO2 uptake; decarboxytlation of stored malate and refixation of internal CO2; deacidification of leaf