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69 terms

AP Bio - photosynthesis - basics

STUDY
PLAY
mesophyll
the tissue interior of the leaf
stomata
microscopic pores in leaves
stroma
dense fluid within chloroplasts
thylakoids
membranous sacks within chloroplasts
grana
stacks of thylakoids
the formula for photosynthesis is
6CO2 + 6H2O + light energy = C6H12O6 + 6O2
the oxygen given off is derived from ____
water
does photosynthesis require energy?
yes (provided by light)
the 2 stages of photosynthesis
and calvin cycle
in light reactions, light absorbed by chlorophyll drives a transfer of __ and ____ from ___ to _____
electrons, hydrogen, water, NADP+
light or dark reactions give off oxygen as a byproduct
light
the light reactions use _____ to reduce NADP+ to ____ by adding ____
solar power, NADPH, a pair of electrons along with H+
the light reactions also generate ___, using ____ to power photophosphorylation
ATP, chemiosmosis
photophosphorelation
addition of phosphate group to ADP
light energy is initally converted to chemical energy in the form of ____ and ____
NADPH, ATP
light reactions produce no ____
sugar
the Calvin cycle begins
by incorporating carbon into organic compounds - carbon fixation
carbon fixation
the incorporation of carbon into organic compounds
the calvin cycle reduces its fixed carbon to ____ by addition of ___
carbohydrate, electrons
the reducing power within the Calvin cycle is provided by
NADPH
to convert CO2 to carbohydrate, ___ produced by light reactions is needed
ATP
light reactions occur in the ______ and calvin cycle in _____
thylakoids, stroma
the _____ the wavelength, the greater the energy
shorter
spectrophometer
machine to measure the ability of a pigment to absorb light
chlorophyll a
works best with violet blue and red (blue-green)
action spectrum
the effectiveness of driving the action
chlorophyll b
yellow-green
carotenoids
hydrocarbons of yellow and orange; function as photoprotection: absorb and dissipate excessive light energy
a pigment can only absorb photons with energy
that equals the energy difference between the ground state and the excited state
photosystem
composed of a reaction center surrounded by a number of light-harvesting complexes
light-harvesting complex
consists of pigment molecules bound to particular proteins
reaction center
protein complex that includes 2 special chlorophyll a molecules and a molecule called primary electron acceptor
the chlorophyll a molecules within the reaction center are special because
their location enables them to use the energy from light to boost one of their electrons to higher energy level
the 1st step of light reaction is
the solar-powered transfer of an electron fro ma special chlorophyll a molecule to the primary electron acceptor
there is a ____ reaction within a photosystem
redox
photosystems I and II are in
the thylakoid membrane
each photosystem I or II has a characteristic reaction center
a particular kind of primary electron acceptor next to a pair of special chlorophyll a
noncyclic electron flow
the predominant route of electrons through photosystems I and II
cyclic electron flow
a way of transporting electrons through photosystem I but not II
cyclic electron flow produces
ATP (no NADPH, unlike non cyclic)
chloroplasts generate ATP by
chemiosmosis
the chloroplast's system for chemiosmosis is _____ to mitochondria because
similar, ATP synthase complexes similar, electron carriers similar
chemiosmosis in chloroplasts is different from mitochondria in that
chloroplasts do not need food to drive the reaction, and spacial organization
the _______ ______ of the chloroplasts is the H+ reservoir
thylakoid membrane
the pH gradient across the membrane is
substantial
light reactions, summarized:
noncyclic electron flow pushes electrons from water, where they are at a lowe state of potential energy, to NADPHS, where they are stored ast a high state of potential energy. The light driven electron current also generates ATP. Thus, the equipment of the thylakoid membrane converts light energy to chemical energy stored in NADPH and ATP.
The Calvin cycle is _____
anabolic (makes sugar)
glyceraldehyde-3-phosphate (G3P)
the direct product of Calvin cycle (net synthesis comes from 3 CO2)
RuBP
5-carbon sugar that CO2 is attached to when it enters Calvin cycle
rubisco
enzyme that catalyzes the 1st step of the Calvin cycle
G3P
a 3 carbon sugar; for each CO2 are formed in the Calvin cycle; 1 leaves to be used in the cell, 5 are use for regeneration of RuBP
___ RuBP are made from ___ of G3P in 1 calvin cycle
3, 5
the net synthesis of 1 G3P molecule requires:
9 ATPs, 6 NADPH
The G3P that leaves the Calvin cycle is used for
starting material for metabolic pathways that synthesize other organic compounds
transpiration
the evaporative loss of water from plants
photorespiration
favored on a hot day when their stomata is closed to prevent transpiration, but also doesn't allow CO2 to get in
C3 plants
plants in which the initial fixation of carbon occurs via rubisco
C3 plants' rubisco can bind to ___ instead of CO2
oxygen
photorespiration generates ___ ATP
no (it consumes it)
photorespiration drains away as much as ___% of carbon fixed by Calvin cycle
50
C4 plants
plants that preface the Calvin cycle with alternate mode of carbon fixation that forms a 4-carbon compound
C4 plants have 2 types of photosynthetic cells:
bundle-sheath and mesophyll
bundle-sheath cells
tightly packed sheaths around the vein of the leaf within a C4 plant
mesophyll cells
more loosely arranged cells between the bundle sheath and leaf surface cells (C4)
in the C4 plants, the calvin cycle is confined to the _____
bundle sheath (but the cycle is preceded by incorporation into organic compounds into the mesophyll)
PEP carboxylase
enzyme that aides in carrying out the C4 pathway within the mesophyll cells; it has no affinity for O2
CAM plants
ones that open their stomata during the night
the mesophyll cells of CAM plants store ______ they make during the night
organic acids
the difference between CAM plants and C4 plants is
in CAM plants, the carbon fixation and Calvin cycle takes place within the same cell but at different times, while in C4 plants, they places where the two events take place are structurally separated