Ch. 7 Photosynthesis Flashcards
how has the industrial revolution affected CO2 levels in the atmosphere?
- fossil fuels/pollution increased CO2 levels
- deforestation/development increased CO2 levels
- not as many plants take up the CO2 through the processes of carbon sequestration
carbon sequestration
natural uptake of CO2 by plants, especially trees, during photosynthetic process
what does increased CO2 levels do?
- reduced ozone layer (O3): protects from UV rays
- increased greenhouse effect: gives atmosphere the warmth to sustain life
- global climate/warming: some areas getting cooler, some getting hotter
producers
autotrophic organisms
- first autotrophs to fill Earth’s atmosphere with oxygen, creating the ozone layer
- get carbon from atmosphere
- get energy from photosynthesis or chemosynthesis
photoautrophs
capture sunlight energy and use it to carry out photosynthesis
- plants
- many protists
- some bacteria
- algae: great producers of O2 in the oceans
consumers
heterotrophic organisms
-get carbon from consuming autotrophs and/or other heterotrophs
decomposers
break down waste products/dead matter and recycle nutrients back into the environment
-bacteria, fungi, protists
photosynthesis equation
12H2O+6CO2–> 6O2+C6H12O6+6H2O
photons
packets of light energy (radiation) that travel in vibrating particles
- each type of photon travels as wavelengths with a fixed amount of energy
- photons having the most energy travel as the shortest wavelength
visible light
the white light you see through a prism as colors of a rainbow
pigments
molecules that absorb different wavelengths of light
- act as an ‘antenna’ to absorb the light energy from the sun
- found in the plastids of plants
what is color?
color is the pigments that are being reflected
why are plants green?
green is reflected because it is not as efficient for driving photosynthesis
most efficient is violet and red
chlorophylls
main pigments seen in most autotrophs because others are being absorbed for photosynthesis
chlorophyll a
reflects blue-green
chlorophyll b
reflects yellow-green
carotenoids
reflects orange, reds, yellows
anthocyanins
reflects red, purple, blue
phycobilin
reflects blue-green, red
what are some leaf characteristics?
- palisade mesophyll
- spongey mesophyll
- guard cells
palisade mesophyll
upper surface of leaf responsible for greater photosynthesis because it’s densely packed with chloroplasts
spongey mesophyll
lower surface of leaf responsible for less photosynthesis because chlorophyll is dispersed in a spongey arrangement
guard cells
appears in the lower surface of the leaf and borders the stomata
-responsible for gas exchanges
when filled with water: stoma opens
when shrunk from drought: stoma closes
where are pigments found?
- some protists
- bacteria (cyanobacteria)(plasma membranes)
- plants (plastids) (TMS)
what are photosystems?
clusters of proteins and pigments in plastids of a plant that capture energy rather than allowing it to escape as light and heat
photolysis
when sunlight breaks down water in photosystems into free electrons, hydrogen, and oxygen
two types of photosystems
- photosystem I (P700)
- photosystem II (P680)
photosystem I (P700)
a cyclic pathway of ATP formation- most ancient,
- no O2 could be made
photosystem II (P680)
a non-cyclic pathway of ATP and NADPH formation
- most recent and O2 is made
light dependent reaction
the “photo” part
- takes place in the TMS, specifically the grana
- ATP and NADPH is made
light independent reaction
the “synthesis” part
- takes place in the stroma
- sugar molecules are made
where is sunlight energy trapped?
on the chloroplast
grana
photosynthetic stacks which trap sunlight energy
stroma
fluid-filled portion were sugars and starches are stored
3 functions of glucose/ sugar phosphates
- cellular respiration
- cellulose (for structure)
- starch storing molecules
How does the light-dependent reaction occur?
- photolysis of water: sunlight energy is trapped in pigments and breaks down water
- ATP is formed by phosphorylation
- hydrogen carriers are formed: NADP+H = NADPH
what are the products of the light (dependent) reaction?
- NADPH: electron carriers that deliver hydrogen and electrons to build organic molecules
- O2: a by-product of photolysis released into atmosphere
- ATP: delivers energy by releasing phosphates to drive the independent reaction
how does the light-independent reaction occur?
- NADPH: delivers electrons and hydrogen
- CO2 diffuses into the stroma to deliver carbon and oxygen to build sugars through “carbon fixation”
- ATP drives the reactions through the light independent reaction to produce a phosphorylated glucose
RuBP
ribulose bisphosphate
- accepts more CO2 during light-independent reaction+ carbon fixing
C3 plants
normal plants
- can close stomata in hot conditions to conserve water
- photosynthesis only runs when stomata is open
-this causes CO2 to not enter and O2 build up
so O2 combines with RuBP instead of CO2
C4 plants
thrive in hot, dry climates
-normally close stomata in hot, dry conditions, photosynthesis runs anyways
-photosynthesis occurs in bundle sheath cells
-photosynthesis can still run where stomata is closed
-fix carbon 2 times, and produces oxaloacetate
(crab grass, sugarcane, corn)
CAM plants
found in desert climates
-open stomata and fix carbon only at night
-use C4 cycle to break down crassulacean acid to CO2 to enter the dark reaction
(cacti, succulents)
