AP Bio - photosynthesis - basics

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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

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