PHOTOSYNTHESIS PART 1 Flashcards
In photosynthesis, _____ assimilated to form
carbohydrate and oxygen
CO2
Chemical energy used to utilized in enzymatic reactions that convert
CO2 into organic molecule
NADPH and ATP
Formula of Oxidation of water
2H2O → 4 electrons + 4 protons + O2
How does Reduction of CO2 forms organic compounds
through the transfer of e- from donor to acceptor molecule
What is the equation of photosynthesis?
6 CO2 + 6 H2O ———–> C6H12O6 + 6 O2
What is the equation of respiration?
C6H12O6 + 6 O2 ———–> 6 CO2 + 6 H2O
Turning Chemical Energy into Fuel for Growth,
Development and Reproduction
Respiration
Since growth requires a net gain of energy – in
plants, photosynthetic energy gain must exceed
______________
respiratory energy loss
What is the photosynthetic tissue?
Messophyl
Drought-Stressed Plants Give off more
_________ Wavelengths
Infrared
Under carotenoids
- Carotene ±
- Xanthophyll ±
the pigment that initiates the
light dependent reactions of PS; bright green
Chlorophyll a
accessory pigment; yellow green
difference: methyl group (-CH3); carbonyl (-CHO)
Chlorophyll b
- yellow and orange
- expands the spectrum of light that provides
energy
Carotenoids
electrons in pigment molecules
absorb photons of light energy, which results to what?
boosting electrons to a higher energy level
Carotenoid functions
- Antenna pigments
- Photoprotection *
the condition in which all its
electrons are in their normal, lowest-energy
levels (dissipates as heat or as an emission of
light of a longer wavelength than the absorbed
light, fluorescence)
Ground state
Reactions where
* Light energy is transferred to ATP and NADPH
* Water molecules are split, releasing O2
Light-dependent reactions
Reactions where
Energy in ATP and NADPH drives synthesis of
glucose and other carbohydrates from CO2 and
water
Light-independent reactions
- include chlorophyll, accessory pigments
- organized with pigment-binding proteins into
antenna complexes
Photosystems
- special pair of chlorophyll a molecules
- release energized electrons to acceptor
Reaction center
- reaction center for photosystem I
- P700
- reaction center for photosystem II
- P680
Electrons lost from photosystem II are
replaced by what?
photolysis of water molecules,
which dissociate into hydrogen ions and
oxygen
- Process by which light energy breaks down a
molecule such as water
- Photolysis
- A light-driven reaction that attaches a
phosphate group to a molecule
Photophosphorylation
- Electrons cycle within photosystem I
Cyclic photophosphorylation
- Electrons move from water to
photosystem II, to photosystem I, to
NADPH
Noncyclic photophosphorylation
It is an example of how organisms harvest
energy from their environment
Energy Flow in
Photosynthesis
first step in light-
dependent reactions
- Entry of electrons from a photosystem into the electron transfer chain
- ATP forms in the _______
- Electron energy is used to build up a ___________
across the membrane - H+ flows through __________, which attaches a
phosphate group to _____
-stroma
-H+ gradient
-ATP synthase
-ADP
Electrons lost from a photosystem enter an
_____________________ in the thylakoid
membrane
electron transfer chain
Organized arrays of enzymes, coenzymes, and
other proteins that accept and donate electrons
in a series
Electron transfer chains
Outputs of Non-cyclic Electron Flow
- ATP (non-cyclic photophosphorylation)
- O2
- NADPH
It is synonymous to Photolysis of Water
(Hill reaction)
PS I and II are _____segregated
spatially
PS I and ATP synthase located exclusively in
the ______thylakoids and _________ of thylakoids (regions where the
membranes are not paired to form grana)
-stroma
-non-appressed
regions
PS II is present only in _______ regions of
grana thylakoids
appressed
uniformly
distributed throughout both regions
Cytochrome b6/f complex
- ETC 1 (P680)
- Primary electron acceptor: _____________
- via carriers : p_______________ – __________
→ ______________→ ____________ (PC)
-pheophytin (pheo)
-plastoquinone (PQ)
-H carrier
-cyt b/f complex
-plastocyanin
ETC 2 (P700)
* Primary electron acceptor:____
*_______________→ NADPH
-A0
- Ferredoxin (Fd)
The coenzyme NADPH forms in a
pathway that also releases
_______
oxygen
Enzyme-mediated reactions that build sugars in
the stroma of chloroplasts
Calvin-Benson cycle
- Extraction of carbon atoms from
inorganic sources (atmosphere) and
incorporating them into an organic
molecule - Builds glucose from ____
- Uses bond energy of molecules
formed in light-dependent reactions (ATP, NADPH)
-Carbon fixation
-CO2
3 phases of carbon fixation
- CO2 uptake phase
- Carbon reduction phase
- RuBP regeneration phase
- Enzyme rubisco
- (ribulose bisphosphate carboxylase/
oxygenase) - combines CO2 with ribulose
bisphosphate (RuBP), a five-carbon
sugar - forms 3-carbon phosphoglycerate
(PGA)
CO2 Uptake
Phase
what does For each 6 CO2 fixed
- 12 G3P are produced
- 2 G3P leave cycle to produce 1
glucose
- Remaining G3P molecules are modified to
regenerate RuBP
RuBP
Regeneration
Phase
dissipate excess ATP and
reducing power under conditions
of high light intensity, thus
preventing damage to chloroplast
Photorespiration
Cells under photorespiration
Chloroplasts, Peroxisome, Mitochondrion
- Rubisco acting as an oxygenase, catalyzes
the reaction of RuBP and O2 forming
phosphoglycolate (2-C compound) in
addition to PGA in the chloroplast - Phosphoglycolate is rapidly converted to
_________ - PR is a light-induced respiration occurring in
green tissues as a response to ______________________
-glycolate
-low CO2/O2
ratio
_____________: RuBP is oxygenated to form
phosphoglycolate → glycolate
Chloroplast
_____________:glycolate is oxidized /converted
to glycine
Peroxisome:
_________: glycine (2 molecules)
metabolized into serine (releasing ammonia
and CO2)
Mitochondria
- occurs more at high temperature and high
irradiance due to: - the substrate specificity of rubisco shifts in favor
of O2 as temperature increases; - leaf of CO2 concentration becomes very low at
high irradiance largely due to rapid
photosynthesis; the low [CO2] favors
oxygenation
Photorespiration
- Internal cellular recycling of 3 gases: CO2, O2 and NH3
- Glycolate synthesis in the leaf can decrease toxic levels of oxygen
- Physiological defense against high irradiance and thermal load (dissipation
of excess photochemical energy) - Contribution to cell amino acid pool (Gly; Ser)
- Response to niche diversificaiton scheme
Importance of Photorespiration
Examples of C3:
rice, tobacco, soybean
C3 is about Each turn of the cycle: fix one molecule of
CO2; input: ____________- and ______________; product:
G3P/Triose phosphate (TP)
* 1 TP = _____________ : 6 CO2 = _____________
-3 ATP and 2 NADPH
-3 turns (3 CO2)
-hexose
C4 or __________________
examples:______________________
* Substrate: __________ instead of CO2
* First Stable Product: ___________________
-Hatch-Slack Pathway
-corn; sugarcane
-HCO3
-4-C oxaloacetate
- It reduces photorespiration and water loss
C4 or Hatch-Slack Pathway
____________________ (CAM)
* similar to C4 pathway
* PEP carboxylase fixes carbon at night
* in _______________ cells
* Calvin cycle occurs during the day
* Examples: ________________________
-Crassulacean acid metabolism
-mesophyll
-succulents, cactus, pineapple
- main form of translocatable carbohydrates in
plants - synthesized outside the chloroplast —cytosol
- Sucrose
- synthesized in chloroplast stroma where it is
built up during the day and used as energy
source at night - produced and stored in amyloplast
- Starch
Factors Affecting
Photosynthesis
Light
CO2 availability
Temperature
Water
Nutrients
Leaf Age
Carbohydrate translocation
