Lecture 9 Flashcards
how droughts worsen climate change
by causing reduced carbon sequestration
(capturing and storing CO₂ from the atmosphere to prevent it from contributing to global warming and climate change)
by =
reducing growth
= slower plant growth = reduced biomass production = less Co2 sinks = less abosrption of CO2
dec photosynthesis
= undergo water stress bc of scarcity of water = leave stomata closes = prevents water loss = but at the same time prevents absorption of CO2, = so less taken out of atmo = buildup in atmo
2 stages of photosynthesis
both in chloroplast
1.
light dependent + involves chlorophyl pigments
in thyloakoid mb
produces ATP and NADPH
leads to water splitting and O2 production
- light-independent
begins in chloroplast storm and continues in the cytosol.
CO2 fixation (conversion) to produce sugars and other org molecs
pigments
molecs that absorb wavelengths in visible spectrum
absorb light E during photosynth
chlorophyl a and b, and beta-carotene are common in plants
light
form of electromagnetic radiation
dual nature = waves + particle-like behaviours
particles of light = packet of E = photons
amount of E in radiation = inversly prop to wavelength
shorter waveL = greater the E
light absorbed by molecs
molecs in plants absorb only specific wavelengths of light
= photons w specific amount of E
when molec absorb E of a photon,
e- goes from ground state (lower E) to an excited state (higher E)
from close to far from nucleus
from here, e- is either lost to another more e- greedy thing
or e- loses its E in the form of heat or photons/fluoroscence
certain wavelength absorbed ex
chlorophyl absorbs blue nad red wavelengths, reflects green, so gives off green color
a single photosystem is composed of
a rxn centre surr by light harvesting antenna complexes containing chlorophyl
pigments in anetenna system absorb light E and transfer it to chlorophyl dimer (special pair) in the reaction centre = responsible for initiating the conversion of light energy into chemical energy.
from rxn centre to e transport chain
so far, light hits the antenna complexes, E transferred from one chlorophyll molec to another, eventually to chlorophyl special pair.
now,
to mobile e- carrier (plastoquinone)
the high E e- leaves the excited chlorophyl special pair. now has a + charge
** this is the charge separated state**
special pair electron replaced by water lysis = O2 is produced
now mobile carrier delivers high E e- to another complex in thylakoid mb (cytochrome b6f)
cyt B6f uses the E in the e- to pump H+ against gradient, from storm into thylakoid space,
makes a proton electrochemical gradient,
used to produce ATP
Low E e- now passed on to plastocyannin
light produces charge seperation in rxn centre, so
so same thing, goes from chlorophyl to chlorophyl in antenna complex ,then to special par in rxn centre, then transfers it to mobile carrier, now pair has + charge again
to neutralize it, gets e- from plastocyanin,
excited e- from primary accepter given to ferredoxin
then passed on to ferredoxing NADP+ reductase
reduces NADP+ too NADPH
light reaction yields what?
leads to production of ATP, NADPH
O2
ATP and NADPH = activated carriers used to produce org molecules
= converts CO2 to sugars
Calvin cycle has 3 phases
carbon fixation
sugar formation
region of ribulose 1,5-diphosphate
carbon fixation
formation fo covalent bond bn CO2 and ribulose 1,5 diphosphate
catalyzed by rubisco (ribulose biphosphate carboxylase)
results = 2 molec of 3-phosphoglycerate.
1 CO₂ (1 carbon) + 1 RuBP (5 carbons) → something w 6C => 2 × 3-phosphoglycerate (3-PGA) (3 carbons each).
sugar formation
consumption of ATP and NADPH
production of glyceraldehyde 3-phosphater
1 molecule for glyceraldyhde 3-phosphate leaves the cycle, transported out the chloroplast storm into the cytosol for sugar, fat, and aa formation
regeneration phase
regeneration of ribulose 1,5-diphosphate
consumption of ATP
light indirectly stimulates the calvin cycle
some enzymes in Calvin cycle are activated by pH changes made by light in the storm
light induced e- transport reduces disulphide bridges in some Calvin cycle enzyme, = activating them
in plant cells, chloroplast + mito work tog to supply cells w metabolites and ATP
chloroplast inner mb is impermeable to ATP and NADH = stay in there to ne used in carbon fixation cycle
sugars made are either stored in chloroplast or exported tot eh rest of plant cell
then can enter in cell rep in mito to make ATP
mito is permeable to ATP
sun = ultimate source of E
solar E enters the living world through photosynthetic plants
plants obtain E directly from lunlight
animals eat plants or eat animals that eat plants
all animals live on E stored in chem bonds of organic molecs
