photosynthesis outline Flashcards
what did van Helmont do? what did he find out?
he planted a 5 lb plant in 200 lbs of soil and gave it H20 for 5 years. the tree gained 165 lbs, but the soil only lost 2 oz. he concluded plant’s mass comes from water, not soil (incorrect)
what did Joseph Priestly do? what did he found out
covered a candle with a closed contained and found that it burned out. but when he added a mint plant to it, the candle continued to burn. he concluded that the mint “restored” the air that the burning candle depleted without knowing of O2
what did Ingenhouse do?
discovered plants needed light, finishing the photosynthesis mystery
what is photosynthesis?
process by which autotrophs use light energy and convert it to chemical energy to make glucose molecules from carbon dioxide and water
where is chemical energy stored?
stored in C-C C-H bonds in glucose
equation for photosynthesis
6CO2 + 6 H2O+ (6 H2O) + light —> 6O2 + (6H20) + C6H1206
what carries out photosynthesis in plants? where are they located?
chloroplasts in green parts of plants
where are most chlorophylls located?
leaves
where do plants get their green color from?
chlorophyll pigment
where is chlorophyll found?
interior layer called mesophyll
where do CO2 and H2O enter plants from?
stomata
disk like sacs
thylakoid
stack of thylakoids
grana
thick fluid inside inner membrane
stroma
where are chlorophyll molecules found?
inside thylakoid membranes
xylum
H2O transport vein
phloem
sucrose transport vein
layers of a leaf
upper epidermis
mesophyll,
guard cell, stomate
lower epidermis
what type of process is photosynthesis?
redox process
what is oxidized and reduced in photosynthesis? what happens as a result?
water - oxidized
carbon dioxide - reduced
electrons gain energy
what provides energy for electrons to go up the energy hill?
light energy captured by chlorophyll molecules
pathway of energy
solar/light energy –> chemical energy/ATP—> energy stored in glucose
what type of energy is sunlight?
radiation or electromagnetic energy
what light can we see?
visible/white light
what happens as light hits a cholorplast?
pigment molecules in the thylakoids absorb different wavelengths of light
what light does chlorophyll a absorb?
mainly blue-violet and red light, and reflects green light
what does chlorophyll b absorb?
mainly blue and orange, and reflects yellow-green
cartenoids
family of orange colored pigments
carrots, tomatoes, fall leaves
what do chlorophyll b and carotenoids do in photosynthesis?
don’t directly participate in the reactions
broaden the range of light a plant can use and then pass the light energy they absorb onto chlorophyll a
what does chlorophyll a do in photosynthesis?
put the energy received to work in photosynthesis
correlation bw wavelength and amount of energy?
inverse
long wavelength=lower energy
short wavelength=high energy
high energy to low
gamma rays (V)
radiowaves (R)
how many stages does does photosynthesis have?
light dependent
light independent
what are the light reactions?
reactions that require light directly
what do light reactions do? what is this known as?
reactions that convert solar energy to chemical energy and produce 1/2 O2 as a waste product
“photo” part of photosynthesis as it takes energy from light
where does the light reactions of photosynthesis occur?
in the thylakoid membrane of the chloroplast’s grana
what does noncyclic phosphorylation use?
light (photo-)
ADP +Pi (phosphorylation)
what are photons?
discrete packets of energy
what can light behave as?
waves or photons
what happens when a pigment molecule absorbs a photon?
one of the pigment’s electrons gains energy
what does the electron that has gained energy do?
raised from the ground state to an excited stae and immediately loses that excess energy as it it unstable
what is the excess energy released as? (3)
heat
fluorescence
passed to primary electron acceptor
fluorescence
light that is emitted as an electron falls from excited to ground state
how are all pigments in the thylakoid membrane grouped?
clusters of 200-300 pigment molecules
what donates electrons to the primary electron acceptor?
only one chlorophyll a molecule
reaction center
chlorophyll a and primary electron acceptor
what does chlorophyll a pigments and other pigments molecules act as?
function together as light gathering antennae that absorb photons and pass the energy along the pigment molecules until it reaches the reaction center
photosystme
combination of antenna pigment molecules, reaction center, and primary electron acceptor
2 types of photosystems in light reactions
photosystem II and I
what is the name of chlorophyll a name in photosystem II? why?
P680 as the wavelength it absorbs best is 680 nm (orangish-red)
what is the name of chlorophyll a name in photosystem I? why?
P700 as the wavelength it absorbs best is 700 nm (red)
what happens to each primary electron acceptor after it gains electrons?
gets oxidized as it loses as electron down the ETC
what is the energy lost down the electron transport chain used to do in photosystem II?
make ATP
what happens to this energy lost down the ETC used to do in photosystem I?
temporarily stored in the coenzyme NADPH
reaction for NADPH production
NADP+ + 2e- + H+ —> NADPH
what does every molecule of NADPH need to form?
2 electrons from photosystem I
where does photosystem I get its electrons?
from the bottom of the first ETC
where does photosystem II get its electrons?
photolysis - splitting of H2O
it leaves behind 2 H+ and 1/2 O2
what does the waste oxygen atom do?
combines with another oxygen atom to make O2 that will be released from the stomata that guard cells let them through from
stomata
opening of the bottom of leaf
what are the products of light reactions?
ATP, NADPH, 1/2 O2
how are NADPH and the O2 waste products formed?
redox reactions in the thylakoids
how is ATP formed in light reactions?
chemiosmosis
summary equation for light reaction
H2O + light +ADP + Pi + NADP+ + 2e- + H+ —-> 1/2 O2 + 2e- + 2H+ + ATP + NADPH
what drives the H+ from the stroma to the lumen of the thylakoid? what does this create?
energy released during the ETC;
H+ gradient with potential energy to drive ATP synthesis
photophosphorylation
making of ATP
what is the final electron acceptor in 2nd ETC?
NADP+ not O2
difference between cyclic phosphorylation and non cyclic phosphorylation?
cyclic uses a simpler pathway to generate ATP and is only used when NADP+ is not around to accept electrons, so it’s not as efficient
function diff between cyclic and noncyclic?
electrons in photosystem I are excited like normal and leave P700, onto to be passed along the ETC of photosystem II and returned back to P700
the calvin cycle different names
calvin-benson cycle
light-independent reactions
dark reactions
C3 photosynthesis
purpose of calvin cycle
make glucose
where does the calvin cycle take place?
stroma of the chloroplast
what does the calvin cycle require?
CO2 from the air
ATP and NADPH made in the light reactions
what is the energy to make sugar in the calvin cycle?
ATP and NADPH
what is the carbon source for the calvin cycle?
CO2 molecules
what does the Calvin cycle do with the CO2
carbon fixation - fixes it from the air and converts it into carbohydrates
how many spins does it take to make a 6 C glucose from the calvin cycle?
must repeat 6 times as it takes in only one CO2
how many spins does it take to make 1 PGAL molecule?
3- 3CO2 molecules are needed
how many PGAL molecules are needed to make glucose?
2 to make 1
what happens once CO2 enters the calvin cycle in the stroma?
combines with a 5 C molecule called RuBP (ribulose biphosphate) to form an unstable 6 C compound with the aid of rubisco-an enzyme
what happens to this 6 C compound?
quickly breaks down into 3 carbon compound 3-PGA (phosphoglycerate)
why is the calvin cycle also called C3 photosynthesis?
first stable product formed is 3 carbon PGA molecule
how are ATP and NADPH used?
for each spin 2 ATP and 2 NADPH are oxidized to produce energy rich 3 carbon molecule called PGAL (Phosphoglyceraldehyde) / G3P (glyceraldehyde 3-phosphate)
when does PGAL leave the cycle?
until 3 spins are made
how many PGALs are made in one spin?
1
if 3 CO2 enter the calvin cycle, how many intermediates are there? 3-PGA? ATP? NADPH? PGAL/G3P?
3 six carbon intermediates
6 3-PGA
6 ATP
6 NADPH
6 PGAL/G3P
what happens when one PGAL leaves the cycle?
the other 5 with the aid of 3 ADP is converted back to 5 carbon RuBP continuing the cycle
how many times does the carbon cycle happen?
x2
it takes 3 CO2 to release 1 PGAL
so 6 CO2 to release 2 PGAL
that will make one glucose
what can the 2 PGALS make beside glucose?
fructose or sucrose
or make many glucoses to make starch or cellulose
do the reactions in the calvin cycle occur spontaneously?
no-enzymes catalyze every product in photosynthesis
coenzymes and cofactors are also involved
coenzyme
organic - NADPH
cofactor
inorganic - metal ions
what do cofactors and coenzymes do?
fit in active site for other substances to bind
how does the calvin cycle use light?
although it is called the dark reaction, it used light indirectly as it dependents of ATP and NADPH made in light reactinos
equation for calvin cycle?
6CO2 + 18 ATP+ 12 NADPH–> C6H1206 + 18 ADP + 18Pi + 12 NADP+ +12H+ + 24e-
C3 plants. examples?
plants in which the Calvin cycle used CO2 directly from the air and first compound made is 3-PGA
wheat, rice, oats
what is the problem with C3 plants?
in hot dry days, they close their stomata to prevent H2O loss, but also blocks CO2 from entering and O2 from leaving
what happens as CO2 levels get down and O2 get up in C3 plants?
C3 photorespiration occurs - rubisco incorporates O2 instead of CO2
how is photorespiration different from photosynthesis? cellular respiration?
it yields no glucose; yields no ATP
what is photorespiration believed to be?
an evolutionary relic when atmosphere had much less O2 and more CO2
what does photorespiration drain away?
50% of the carbon fixed by the Calvin cycle and lowers crop yields
what do C4 plants do?
their first product in the calvin cycle in a 4 C compound
keep stomata closed to prevent water loss, but still make glucose by photosynthesis
what enzyme do C4 plants have? what does it do?
PEP carboxylase that fixes carbon into 4 C oxaloacetate instead of 3 C 3-PGA
this enzyme cannot fix O2, and can continue to fix carbon when CO2 levels are low
what happens to oxaloacetate?
gets converted to malate then acts as a carbon shuttle which donates CO2 to a bundle sheath cell
what is a bundle sheath cella?
cell which keeps making sugars even though the stomata are closed most of the time
examples of C4 plants? how did these become C4?
corn, crab grass, sugar cane;
evolved in the tropics as it is advantageous
what type of photosynthesis do C4 plants do?
C4 photosynthesis
how is C4 photosynthesis separated?
spatially separated
CAM
crassulacean acid metabolism
third mode of carbon fixation and water conservation
CAM plants
pineapples, cacti, most succulent (very juicy tissue)
adapted to extremely dry climates
what does a CAM plant do?
conserves water by opening its stomata and admitting CO2 only at night
what happens when CO2 enters the leaves in CAM?
fixed into oxaloacetate during the night and then releases it as CO2 to the calvin cycle during the day, keeping photosynthessis operating during the day even when there isnt CO2
where does C3 photorespiration take place?
mesophyll
result of C3 photorespiration?
no sugar
where does C4 photosynthesis take place?
makes 4C in mesophyll
makes sugar in bundle sheet
result of C4 photosynthesis?
sugar
where does CAM takes place?
4C during the night in mesophyll
sugar during the day in mesophyll
results of CAM
sugar
