chapter ten part one Flashcards
2 types of organisms
heterotrophs and autotrophs
autotrophs
“self-feeders”
- sustain themselves w/o eating anything
- producers - ultimate source of organic molecules
heterotrophs
unable to make own food, live on compounds produced by other organisms
- consumers - herbivores, carnivores, decomposers (fungi/prokaryotes)
chlorophyll
green pigment that gives leaves color
- in thylakoid membranes
mesophyll
tissue in interior of leaf
- 30-40 chloroplasts per mesophyll cell
- thylakoid
thylakoid
membranous sacs
- grana - columns of thylakoids
stomata
microscopic pores typically on underside of leaf where CO2 enters and O2 leaves
photosynthesis balanced equation
6CO2 + 6H2O + light –> C6H12O6 + 6O2
who tested splitting of water?
Van Noel by substituting S for O
- challenged the false theory that O2 came from CO2 rather than H2O
process of light reactions
- chlorophyll absorbs a photon, and the electron becomes very excited
- a water molecule is split, providing source of electrons and giving off O2
- excited electrons fall down ETC (PSII, Pq, Cato, Pc, PSI, NADP+ final electron acceptor)
- NADP+ becomes reduced to NADPH
- as energy is released by ETC, H+ ions accumulate in lumen
- H+ gradient used to power ATP synthase, (photophorylation)
photophorylation
excited electron fall down chain, energy released pumps H+ ions into lumen, which drive ATP synthase
what does light reaction produce?
O2, NADPH, ATP
what does the Calvin Cycle need?
CO2, NADPH, ATP
overview of Calvin Cycle
CO2 from air incorporated into organic molecules by carbon fixation, NADPH reduces fixed carbon to carbohydrate
where does the light reaction occur?
thylakoid membrane
where does the Calvin Cycle occur?
stroma
sunlight
electromagnetic energy that travels in waves from the sun
wavelength of visible light
380-750 nm
photons
act like objects/particles w/ fixed quantities of energy
pigments
absorb visible light
what light does chlorophyll absorbs?
red and blue, reflects green
spectrophotometer
measurement of ability of pigments to absorb various wavelengths of light
2 spectrums of spectrophotometer
absorption spectrum and action spectrum
absorption spectrum
graph plotting pigment’s light absorption vs. wavelength
action spectrum
profiles relative effectiveness of different wavelengths of radiation and confirms visible light spectrum of chlorophyll
- illuminates chlorophyll, then plots wavelength against photosynthetic rate
chlorophyll a
key light-capturing pigment that participates directly in light reactions
chlorophyll b
accessory pigment to chlorophyll a
carotenoids
separate group of accessory pigments
- hydrocarbons that are various shades of yellow/orange, absorb violet/blue-green light
- broaden color spectrum of photosynthesis
how do carotenoids broaden the color spectrum of photosynthesis?
- absorb/dissipate excessive light energy that would damage chlorophyll
- interact w/ O2 to form reactive oxidative molecules
reaction center and light center
look on paper
excitation of chlorophyll
absorbing photon boosts electron to orbital of higher energy, pigment molecule in excited state
- drops back, emits photon and heat (fluorescence)
fluorescence
afterglow where protons are given off
Photosystem I
- P700
- absorbs light w/ wavelength of 700 nm (far red)
- comes second
Photosystem II
- P680
- absorbs light w/ wavelength of 680 nm (red)
- chlorophyll a at reaction center
- comes first
difference between PSI and PSII
- identical chlorophyll a molecules
- associate w/ different proteins which affects electron distribution and light absorption
noncyclic electron flow
- PSII absorbs light
- electrons taken from water - O2 produced
- electrons more from PII to PI via carriers
- ATP made as electrons move to PI (chemiosmosis)
- 2nd absorption of light in PI raises e to higher level
- ferredoxin (Fd) carries electron to NADP_
ferredoxin (Fd)
protein that carries electron to NADP+ in ETC
carriers that move electrons from PII to PI
- plastoquinione (Pq)
- cytochromes
- Plastocyanin (Pc)
