Chapter 10 Flashcards
what is photosynthesis and its purpose
converts solar energy into chemical energy
photsynthesis equation
CO2 + H2O + light energy —> (CH2O)n + O2
autotrophs
- don’t eat anything derived from other organisms
- producers
- produce organic molecules from CO2
heterotrophs
- obtain organic material from other organisms
- consumers of biosphere
- depend on photoautotrophs
what type of reaction is photosynthesis
redox
- uses energy to build carbs
what are the 2 steps of photosynthesis
- light dependent reactions
- Calvin cycle (light independent reactions)
light dependent reactions
- produce O2 from H2O
- water is split to form O2
- ATP is produced
what happens to electrons in the light dependent reactions
- get excited by light energy
- high energy electrons are transferred to electron carrier NADP+ to form NADPH
what does the Calvin cycle use to reduce CO2
electrons and ATP
what does the Calvin cycle produce
sugar from CO2
where does photosynthesis take place
chloroplasts
how many membranes do chloroplasts have
2
thylakoids
- 1 big membrane folded on itself
- form grana stacks
- contain large quantities of pigment
lumen
space inside thylakoid
stroma
- space surrounding thylakoids
what is the most common pigment in thylakoids
chlorophyll
- reflects green light
accessory pigments
absorb and reflect other colors
what type of light do plants primarily use
red and blue light
- red light= 700 wavelength
- blue light= around 380 wavelength
pigments
- different pigments absorb different wavelengths
- wavelengths are reflected or transmitted
chlorophylls
- absorb= red and blue light
- reflect= green light
1. chlorophyll a
2. chlorophyll b
carotenoids
- absorb= blue and green light
- reflect= yellow, orange, and red light
- absorb excessive light that damages chlorophyll
photon
particle of light
difference between chlorophyll a and chlorophyll b
chlorophyll a is main photosynthetic pigment while chlorophyll b broaden the spectrum used
what happens when pigment absorbs light
goes from ground state to an unstable excited state
how does florescence hapopen
excited electrons fall back to ground state and photons are given off
photosystem
chlorophyll molecules that work together
- 2 major components
1. antenna complex
2. reaction center
what are the two types of reaction centers
- photosystem 1
- photosystem 2 (happens first)
what is the purpose of the photosystems
work together to produce enhancement effect and increase photosynthesis
-abosrb light, transfer energy and electrons
primary electron acceptor
accepts an excited electron from chlorophyll a
- start button to photosynthesis
what is the ultimate primary electron acceptor
reaction center complex
photo phosphorylation
proteins building up to make ATP synthase move and turn to release energy
photosystem 2
- water splitting complex to keep assembly line going
- sunlight triggers excitement of electron
photosystem 1
- lose some excitement when enter and then become more excited again because they tap into a different wavelength of light
- low energy electrons are re-generated
- reduce NADPH+ to NADPH
why does photosystem 2 split water
to replace electrons lost
what are the 3 phases of the Calvin cycle
- fixation
- reduction
- regernation
fixation
- CO2 reacts with ribulose (5 carbon compound)
- results in 6 carbon molecule splitting into two 3PGA (3 carbon molecule)
- converts, interacts, and fixes CO2 into sugar
reduction
- 3GPA are phosphorylated by ATP and reduce NADPH
- produce G3P
- making sugars and then sugar is released
regeneration
remaining G3P is used in reactions that use ATP
G3P
- converted to whatever plant needs
- sugar
where does the calvin cycle occur
stroma of chloroplasts
what does one turn of the calvin cycle fix
one molecule of CO2
what does three turns of the calvin cycle do
- fixes 3 CO2
- produces 1 molecule of G3P
- 3 regenerated RuBP
how many times does the calvin cycle have to occur to produce 1 molecule of glucose
6 times
rubisco
- very slow enzyme
- slows rate of CO2 reduction
- drawn to both O2 and CO2 so they compete
- used in C3 plants
what happens if there is no CO2
calvin cycle stops and a lethal backup of electrons occur
photrespiration
undoes photosynthesis
- serves as damage control
- consume oxygen and releases fixed CO2
stomata
pores that allow gas exchange
what comes from light reactions
- ATP
- electrons
- O2
what come into light reactions
- sunlight]
- water
- electrons
what is the reaction center
start button for photosynthesis
C3
- normal plant
- mesophyll
when does photosynthesis occur in C3 plants
all at the same time
C4
- tropical plants
- 4 carbon compound
- bundle sheath
- spacially divide steps of photosynthesis
- carbon fixation and Calvin cycle occur in seperate cells
CAM plants
- photosynthesis occurs at different times of day
- dessert plants
- form 4 carbon compound
- open stomata at night and fix CO2
- release CO2 and run calvin cycle during the day when stomata are closed
PEP carboxylase
- fix CO2 even when CO2 concentrations are low
- fixes CO2 to a 3 carbon molecile in mesophyll cells
- used in C4 plants
where do the light dependent reactions happen
thylakoid in chloroplast
where does the calvin cycle occur
stroma of chloroplast
RuBP
- ribulose bisphosphate
- 5 carbon compound
