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Caitlin_Tan_Block4_MM5 (Stage 1 of Photosynthesis (light reactions…
Caitlin_Tan_Block4_MM5
converting light energy for food
Chloroplast
stomata
where molecules enter the leaf
where molecules exit
example
CO2
O2
stroma
envelope of 2 membranes
dense fluid within the chloroplast
mesophyll
where Chloroplast are found
tissue in the interior of the leaf
thylakoids
elaborate system of interconnected membranous
segregates stroma
interior of the thylakoid
thlakoid space
grana
sacs of thylakoid
chlorophyll
green pigment located within chloroplast
drives the synthesis of organic molecules
Stage 1 of Photosynthesis
light reactions
convert solar energy to chemical
acceptor NADP+
photons
A quantum or discrete amount of light energy
Chlorophyll a
A type of blue-green photosynthetic pigment that participates directly in the light reactions
violet-blue and red light work best for photosynthesis
underestimates the effectiveness of some wavelengths of photosynthesis
action spectrum
relative effectiveness of dif wavelengths of radiation in driving the process
prepared by illuminating chloroplast with light of dif colors and then plotting wavelength against some measure of photosynthetic
does not match absorption spectrum of chlorophyll a
PS II
happens before PS I
Chlorophyll a's P680
pigment that aborbs 680nm the best
red part of the spectrum
PS I
Chlorophyll a's P700
pigment that absorbs 700nm the best
absorbs the far red parts of the spectrum the best
Photophosphorylation
powered up by ATP using chemiosmosis
accessory pigments
Chlorophyll b
almost identical to chorophyll a
difference
functional groups bonded to the porphrin
color
yellow-green
carotenoids
color
yellow or orange
function
broaden the spectrum of colors that drive phtosyntheis
absorbs wavelengths that chlorophyll
photoprotection
biochemical process that helps organisms cope with molecular damage caused by sunlight.
photosystem
composed of a reaction center surrounded by a number of light-harvesting complexes
light harvesting complex
consist
bonded to a particular protein
pigment
chlorophyll b
carotenoids
chlorophyll a
goes to
reaction center
protein complex
1 more item...
electron flow
noncyclic
the net electron flow is from water to NADP+
involves ATP NADPH and O2
cyclic
involves only photosystem I
produces ATP
NOT NADPH or oxygen
Stage 2 of Photosynthesis
Calvin Cycle
Phase 2
Reduction
each of 3 phosphoglycerate receives 1 more phosphate group from ATP
NADPH donates 2 electrons to reduce 1 3-bisphoglycerate to G3P
reduces carboyxl group of 3 phosphoglyerate to the aldehyde group of G3P
G3P
sugar
3 carbon sugar formed in glycolysisby splitting of the glucose
18 carbons
form
6 molecules of G3P
Phase 3
Regeneration of the CO2
carbon skeleton of 5 molecules of G3P are rearrange
Product
Product 3 RuBP molecules are formed
now can receive CO2
spend 3 ATP
Phase 1
Carbon fixation
attach CO2 to ribulose bispohsphate (RuBP
product:
6 carbon intermediate so unstable that it immediately split in half forming 2 molecules 3-phosphglycerate
15 carbons
C3 plants
initial fixation of carbon occurs via rubisco
enzymes add CO2 to ribulose bisphosphate
important in agriculture
examples
Rice
soybeans
wheat
weather
hot, dry days
C3 plants produce less sugar, cuz the declining levels of CO2 in the leaf
photorespiration
peroxisomes and mitochondria rearrange and split this compound
releasing CO2
photo
occurs in the light
respiration
consumes O2 while producing Co2
ATP
consumes ATP
does not generate ATP
produces no sugar
decreases photosynthetic output by siphoning organic material
C4 plants
preface the Calvin cycle with an alternate mode of carbon fixation
product
first product
4 carbon compound
important to agriculture
sugarcane
corn
members of the grass family
leaf anatomy
distinct types of photosynthetic
mesophyll
enzyme PEP carboxylase adds CO2 to PEP
bundle sheath and the leaf surface are more loosely
Bundle-sheath
arranged into tightly packed sheaths around the vein of the leaf
CO2 is released
enters the Calvin Cycle
CAM
carbon fixation
type of metabolism which CO2 is taken in at night and incorporated into a variety of organic acids
CAM PLANTS
store organic acids they make during the night in their vacuoles until morning, when the stomata closes
similar to C4
CO2 released from organic acids made the night before to become incorporated into sugar in the chloroplast
difference from C4
two steps of the carbon fixation occur at separate times within the same cell