Chapter 8: Photosynthesis Flashcards
what is photosynthesis?
process that uses solar energy to convert CO2 and H2O (inorganic) to sugar and O2 (organic)
what is the general formula for photosynthesis?
CO2 + H2O -> CH2O + O2
what occurs for NADPH to be made?
redox reactions
what occurs for ATP to be made?
proton gradient
what type of energy is solar energy?
short term chemical energy
light reactions
proton gradient, atp, NADPH
can atp and nadph be stored, shipped, and used in a different cell?
no has to be used by the cell that make sit
how does short term chemical energy become long term chemical energy?
Calvin cycle (biochemical reactions)
can sugar be stored, shipped, or used right away?
yes
what is chlorophyll and what does it absorb?
pigment (chemical) that absorbs light
absorbs red and blue light
do pigments only absorb certain lights?
yes
what and where do light reactions take place?
they are reactions that directly require light
they are in thylakoid in the grams of chloroplast
what are thylakoids?
green photosynthetic membrane, contains chlorophyll and other pigments
what is the thylakoid lumen?
space enclosed by the membrane
What do chloroplast contain?
outer membrane
inner membrane
thylakoid membrane
thylakoid lumen
granum (stack of thylakoid)
stroma
what is the purpose of light reactions?
to convert solar energy to short term chemical energy (atp, nadph)
what is the input and output put for light reactions?
in: h2o, adp + p, nadp+
out: o2, atp, nadph
how does h2o become o2 in light reactions
in splits and o2 comes out
what is the Calvin cycle?
light independent reactions, they do not directly use light.
they may occur in light or dark but usually during the day
what does makes atp and nadph and then what uses it?
light reactions
Calvin cycle
where does the Calvin cycle take place?
storms of chloroplast
what is the purpose of the Calvin cycle?
fix o2 into sugar
convert short term chemical energy (atp, nadph) to long term chemical energy (sugar)
what is carbon fixation?
converting inorganic c to organic c compounds
why can you ship and store sugar?
it is very stable
what is the input and output out of the Calvin cycle?
in: co2 +c5= rubp, atp, nadph
out: c6= glucose, adp +p, nadp+
what uses solar energy to make atp and nadph?
Light reactions
what uses atp and nadph to make sugar from co2 and h2o?
Calvin cycle
how are light reaction and the Calvin cycle connected?
light reaction uses water
Light reaction produces oxygen
Light reaction produces atp and H+
Adp is recirculated to light energy for recharge
Dark reaction uses carbon dioxide
dark reactions produce glucose
shorter wavelength = _____ energy
longer wavelength = ________ energy
higher
lower
which way does the electromagnetic spectrum run?
shorter wavelengths to longer wavelengths
Violet- red
list the parts of the electromagnetic spectrum from shortest to longest
gamma rays, x -rays, uv, visible light, infrared, microwaves, radio waves
what type of waves does photosynthesis use?
visible light
what is chlorophyll a?
an essential pigment that is part of the reaction center of PS1 and PS11
what are the types of photosynthetic pigments?
chlorophyll a, chlorophyll b, carotenoids
What are the types of accessory pigments and there visible color?
chlorophyll b (green), carotenoids (orange), xanthophylls (yellow)
what are accessory pigments?
they absorb wavelengths of light
can chlorophyll a absorb all wavelengths of light?
no so they can use a broader range of light for photosynthesis by accessory pigments
why are leaves green?
chlorophyll and accessory plants absorb mainly red and blue wavelengths so the other wavelengths which are green are reflected or transmitted
Why does photosynthesis use most wavelengths except green?
because of the abundance of the accessory pigments and chlorophyll a
do pigments do enzyme reactions or absorb light?
absorb light
what is in the reaction center of the photosystem?
chlorophyll a
what is in the antenna complex / light harvesting complex of the photosystem
accessory pigments
____ is absorbed by accessory pigments in the ______ and transferred to the _____ of the photosystem
light
antenna complex
reaction center
what are the two types of reaction centers?
PS 1: P700
PS 11: P680
what happens during electron transport form PS11 to PS 1 in light reactions?
generates proton gradient
synthesis of atp
Split H2O into o2
what happens during electron transport from PS1 to ferredoxin?
synthesis of NADPH (enzymes do this)
what two things are in a photosystem?
antenna system and reaction center
what process is antenna complex absorbing a photon of light and transfers it to the reaction center of photosystem 11
light reactions electron transport form ps11 to ps 1
what transfers light to reaction center?
accessory pigments
what is easily donated to another molecule during absorption of light by ps11?
the excited electron of chlorophyll a in P680
what is the reaction center of PS11?
P680
what happens after PS11 absorbs a photon of light?
the excited electron is passed down the chain until it reaches PS1
What is the process of electron transport from PS11 to PS1?
PS 11 -> plastoquinone (PQ or QB) -> cytochrome complex -> plastocyanine (PC) -> PS1
what are the mobile electron carriers for PS11- PS 1?
plastoquinone (PQ or QB)
plastocyanin (PC)
When are H+ pumped across the membrane?
during electron transport of ps11 - ps1
Ps 11 has lost an electron and cants absorb another photon of light until
the electron is replaced
what is h2o splitting?
2 h2o -> o2 + 4H+ + 4e-
In h2o splitting, what is 4H+ and o2?
4H+: Contributes to H+ gradient
O2 is made as a by product
What filled the hole in PS11?
electrons from water
where does h2o splitting occur?
oxygen evolving complex (OEC), part of PSII
What are the purposes of electron transport from PSII to PSI?
generate a proton gradient
H+s moved from stroma to thylakoid lumen during electron transport (cytochrome complex)
water splitting releases H+s into the thylakoid lumen
H+ gradient will be used by ATP Synthase to make atp
What is the ph of the stroma and thylakoid lumen?
ph 7-> 8 (basic)
ph 7-> 4 (acidic)
what process is when antenna complex’s absorbs a photon of light and transfers it to the reaction center of PSI
light reactions electron transport from PSI
Are PSI and PSII together?
no they have separate centers and complexes
in absorption of light by PSI, what is easily donated to another molecule?
excited electron of chlorophyll a in P700
What is P700?
the reaction center of PSI
after PSI absorbs a photon of light the excited electron is passed down the chain until it reaches
ferrodoxin
what is ferredoxin?
the final electron acceptor in PSI and is a protein
what and how does ferrodxin produce?
it reacts with the enzyme ferredoxin NADP reductase (FNR) to make NADPH
what is the redox reaction for electron transport from PSI
PSI-> ferrodoxin
ferredoxin (red) + NADP+ -> NADPH + ferredoxin (ox)
how are the electrons replaced in PSI and PSII?
1- electrons from PSII
2- water is split and those electrons are used
what is made form light reactions?
NADPH and ATP
what process makes O2 and H+ in PSII?
h2o splitting
what is the energy in a proton gradient used to make?
ATP by enzyme ATP synthase
What is the process of atp synthesis called?
chemiosmosis: oxidative phosphorylation
how does atp synthase compare in the mitochondria and chloroplast?
almost identical
Light reactions
Function
Location
4 parts
to make atp and nadph
thylakoid membrane of chloroplast
electron transport to make nadph, split h2o, make proton gradient, make atp
what is the first reaction of the Calvin cycle?
co2 + ribulose bisphosphate (C5) -> 2 phosphoglyceric acid (C3)
What enzyme does the first reaction of the Calvin cycle?
Rubisco
where is the Calvin cycle?
stroma of chloroplast
what does oxygenase?
adds O2
what 2 reactions does rubisco perform?
carboxylase activity: carbon fixation
oxygenase activity: photorespiration
what is carbon fixations formula?
CO2 + ribulose bisphosphate (C5) -> 2 phosphoric acid (C3)
what is the photorespiration formula?
O2 + ribulose bisphosphate (C5) -> phosphoglyceric acid (C3) (to Calvin to make sugar) + phosphoglycolate (C2) (this is wasted)
What are the 3 parts of the Calvin cycle?
carbon fixation, sugars are rearranged and reduced, regeneration of ribulose bisphosphate
what are the reactants of carbon fixation?
products
enzyme
co2, RuBP (C5)
2 PGA (C3)
Rubisco
what are the “sugars are rearranged and reduced” formula
PGA (C3) ->->-> G3P (C3)
what energy is used for Calvin cycle part 2?
uses ATP and NADPH made in the light reactions
how much of G3P is used as RuBP= reactant and to make glucose?
5/6 RuBP
1/6 glucose
what are the types of photosynthesis and where are they
C3-most plants
C4- corn, sugar cane
CAM- cacti, succulents (desert plants)
What is the 1st stable compound made in C3?
C3 sugar
What is the first reaction of C3?
CO2 + RuPB (C5) -> 2 PGA (C3)
What enzyme is used in C3?
rubisco
what are disadvantages and advantages of C3?
advantages: most efficient type of photosynthesis
Disadvantages: photorespiration
what are types of C3?
Soybeans, most plants
what is photorespiration?
oxygen reacts with the enzyme and it starts breaking down the sugar, this is bad!!!!
why does photorespiration occur?
rubisco reacts with O2 instead of with CO2, in C3 plants
when is photorespiration a problem?
when relatively high O2 compared to CO2
when stomates close: high temperature, low water
when automates close no new gases enter leaf, use up CO2, make more O2
what are the disadvantages and advantages of photorespiration?
advantage: none
disadvantage: breaks down sugar
wastes energy, fixed (organic) CO2
what is the anatomy of a C3 leaf?
epidermis
stomata
mesophyll = photosynthetic tissue
palisade- Tightly packed rectangles
spongy- loosely packed cells
what is the first stable compound in C4?
C4 OAA (oxaloacetate)
what is the first reaction of C4?
CO2 + PEP (C3) -> OAA (C4)
what enzyme is used for C4?
PEP Carboxylase
what are examples of C4?
Corn, sugarcane
what are the advantages and disadvantages of c4?
advantage: No photorespiration
disadvantages: uses more energy to make sugar
need to make special structures=the bundle sheath
What is the anatomy of a C4 leaf?
mesophyll (outer ring): 1st reaction = carbon fixation CO2 + C3 -> C4
bundle sheath (inner ring) : Calvin cycle -> make sugar
What is the reaction and enzyme for C4 part 1in mesophyll?
CO2 + PEP C3 -> OAA C4
OAA C4 -> malate C4
PEP Carboxylase
Why does photorespiration not occur in the C4?
PEP carboxylase can’t react with O2
What does mesophyll not have?
rubisco and Calvin cycle (no photorespiration)
where is malate shipped after mesophyll?
bundle sheaths
What is the reaction for C4 in the bundle sheaths and Calvin cycle and what enzyme?
malate C4 -> CO2 + pyruvate C3
CO2 + RuBP (C5) -> 2 PHA (C3)
Rubisco
Why is there no photorespiration in bundle sheath?
high CO2 in bundles
Why don’t all plants do C4?
at optimal conditions C3 plants can outcompete C4 plants (high CO2, wet environment, moderate temperature)
C4 plants need an extra 2 ATO to fix C into a C6 sugar
C4 plants must expend energy to produce extra enzymes and build bundle sheath cells
Where is spatial separation in C4?
CO2 fixation and the Calvin cycle
What is compensation point?
when amount of O2 made by photosynthesis exactly matches amount of O2 used by respiration
What 2 metabolic processes do plants carry out?
photosynthesis- uses CO2 and h2o to produce o2 and sugar
Respiration- uses o2 and sugar to produce co2 and h2o
when does photosynthesis increase rapidly?
when the lights are turned on
What environmental factors impact photosynthesis?
temperature - cool temp -> lower rate
- Higher rate as temp increases up to a point, stomata closed photorespiration
light intensity - lower rate at low light intensity
- higher rate at high intensity up to a point
humidity/ water availability - rate increases with higher humidity, keep stomata open - no photorespiration
can you have too much light?
yes it can be damaging to the leaves
when do c4 outcompete C3?
hot dry conditions, high light intensity
no photorespiration
When do C3 outcompete C4?
cool/moderate temp, high humidity, low to average light intensity,
C4 costs more energy to make sugars and other structures
what are types of cam?
cacti, sedum, living stones
slow growing desert plants
what is CAM photosynthesis ?
stomates
Calvin cycle
prevents photorespiration and dehydration
opens stomates at night, stores CO2 as malate
carries out Calvin cycle during day
what is CAM reaction during night and enzyme
malate
CO2 + PEP C3 -> OAA C4
stomates open, co2 enters leaf
PEP Carboxylase
OAA C4 -> malate C4
malate is shipped out of chloroplast, stored in central vacuole
what is CAM reaction during night and enzyme
malate
CO2 + PEP C3 -> OAA C4
stomates open, co2 enters leaf
PEP Carboxylase
OAA C4 -> malate C4
malate is shipped out of chloroplast, stored in central vacuole
What is CAM reaction during the day?
malate C4 -> co2 + private C3
stomates close to prevent dehydration
Malate shipped from vacuole back to chloroplast
CO2 used in Calvin cycle to make sugar
When do cam carry out photosynthesis?
during the day with stomates closed
cam: photorespiration and dehydration?
no photorespiration: high co2 because co2 was stored as malate overnight
no dehydration because plants keep stomates closed during day to prevent excess water loss
Similarities between cam and C4
Initial co2
Enzyme
Storage
same reactions, different locations or times
Initial CO2 fixation: CO2 + PEP (C3) = OAA (C4)
Enzyme: PEP Carboxylase
CO2 is stored as a C4 sugar. Later C4 is broken down to release co2 to be used in the Calvin cycle to make glucose
What contains rubisco in C4?
bundle sheaths cells
What contains rubisco in C4?
bundle sheaths cells
