photosynthesis Flashcards
what is the formula for photosynthesis
6CO2+ 6H20 +energy—> C6H12O6 + 6O2
main purpose of light dependent reactions
-(Photo)
- convert light energy into chemical energy in the form of ATP and NADPH, these chemical energy molecules are used in calvin cycle to assemble sugar molecules
main purpose of light independent reactions
- (synthesis)
- use chem energy from light dependent to assemble glucose
- main goal is to assemble glucose
- calvin cycle
location requirments and products for light dependent reactions
- thylakoid membrane
- required: sunlight and water
- products: oxygen, NADPH, ATP
location requirmeents and products for light independent reactions
- stroma
- requires: ATP, NADPH, CO2 and rubp (enzyme)
- products: glucose, NADP+ and ADP
role of photosystem 2
absorb photons of light energy to energzie and transfer electrons and to create a proton gradeint (H+)
role of photosystem 1
prdocue NADPH which is a energy carrier molecules and to generate a proton motive force
where is energy passes in light dependent reactions
along electron accepting cholophyll A molecules called reaction center
2 stages of light dependent reactions
1: captue solar energy and transfer it to electrons through the splitting of water
2: using energy to make ATP and transferring electrons to make NADPH
what is a photsystem
clusters of cholorphyll and other pigments emeded in thylakoid membrane
what is photolysis
splitting of water, occurs in thylakoid lumen
what is NADP+
coenzyme electron carrier
what is NADPH
electron donor that carriers electrons and hydrogen atoms to other molecules
what is chemiosmosis,
synthesizing ATP using energy from H+ gradeint
process of ions moving across a semi permeable membrane from higher concentration to a lower one
ATP synthase
emeded in thylakoid membrane and porvides the only pathway for H+ to move out
reduction reaction
electron transfer in a chemical equation (gain of electron)
oxidizing agent
- always occurs with a oxidation reaction
oxidation reaction
loss of elctrons
reducing agaent
reacts with oxygen
first step in stage 1
- light strikes the cholorphyll photons excite the chlorophyll
- after chlorophyll captures light energy by absorbing photons and passing energy to electrons it is transfer to reaction center
what causes splitting of water
light energy
water is dived into hydorgen ions, oxygen and electrons
oxygen is made and realses into atmosphere (exits stroma)
Hyrdogen ions remain in luem
electron excitation second step in stage 1
electrons are excited and moved from lumen to cholorphyll
- electrons are transferred to PS1 through electron transport chain
what is the electron transport chain
found along the thylakoid membrane, electron moev along this relasesing energy as they move (redox reaction)
every step down the ETC electrons give up some stored potential energy
what happens when electrons reaches PS1
it is hit by light and become excited again
what is energy realsed by PS1 used for
rejoin high energy electrons with hydrogen ions and NADP+ to produce NADPH (final electron acceptor)
how do hyrdogen ions difuse into thylakoid membrane
cannot diffuse out because membrane is impermebale to them so uses chemiosmmosi
- energy realses from Electron tasnport chain pulls hydrogen ions into thyalkoid membrane (against gradeint)
- creates a + channel and a step gradeinent
how is ATP synthesixed in light depndent reactions
using energy from H+ gradeint
what is an action spectrum
sjows relative effectvieness of different wavelengths of light for photosynthesis, reflected by a response in the rate oxygen is released
what is absorbance spectrum
relative amounds of light of different colors a compound absorbs
what are light independent reactions
energy of ATP and reducing power of NADPH are used to reduce CO2 and make glucose
occurs in stroma
what is G3P
converts CO2 into glucose
what is rubisco
enzyme catalszing carbon fixation
what happens in carbon fixation
means carbon atom in CO2 is chemically bonded to a pre existing molecule in stroma
- this molecule is RuBP (5-carbon molecule)
- this results in a six carbon compound that is highly unstable
- this immediately breaks down into 2 identical carbon compounds (3-PGA)
- these 3-carbon compounds are the first stable products
- plants that demonsatte this are called C3 plants
CO2+ RuBP–> unstable C6–> 2C3
what happens in the reduction part of calvin cycvle
- newly formed 3 carbon compound are in a low energy state
- to convert them to high energy they are first activated by ATP and then reduced by NADPH
- this results in 1,3 bisphosphoglycerate (1,3-BPG)
- pair of electron from NADPh reduced 1,3-BPG into G3P
- results in 6 G3P molecules fro 3 CO2
- 1exits cycle to form glucose and other high energy molecules ( 2 G3P forms 1 glucose)
- 5 G3P are used in regeneration phase
what happens in replacing RuBP stage
- most of reduced G3P molecules are used to make more RuBP, energy supplied by ATP is required to break and reform the chemical bonds to make the 5 carbon RuBP from G3P
how many times must the calvin cycle must be completed in order to synthesize one molecules of sugar
6 times
of the 12 G3P molecules prudced in 6 cycles what do each of them do
- 10 are used to regenerate RuBP
- 2 are used to make glucose
light reaction summary
- 6H2O split= photolysis
- 6O2 released in atmosphere
electron move along teasnport chain - 18 ADP to 18ATP in photosytem 2 from the hydrogen ion gradeint
- 12 NADP+ reduced to 12 NADPH on photosytem 1
calvin cycle summary
- 6 moleucles of CO2 combine with 6 molecules of RuBP
-n12 molecules are PGA are formed - 12 NADPh are oxidized
- 18 ATP are consumed
- 12 G3P are formed
- 10 G3P are changed into RuBP
- 2 G3P molecules are converted into glucose
how long can plant carry out light independent reaction if place in the dark
until it runs out of ATP and NADPH supplied by light reaction
why does plant not immediatly produce glucose when placed in the light
must produced ATP and NADPH
- light independent requires products from light dependent
