Learning Outcomes (8-9-10-11) Flashcards
what is the equation for photosynthesis
6CO2+6H2O+light energy→C6H12O6+6O2
light consists of [blank], which are packets of energy
photons
which wavelengths of light does photosynthesis use, since different wavelengths of light carry different amounts of energy
blue (450 nm) and red (680 nm)
Chlorophyll is a pigment that mainly absorbs light at which wavelenghts?
red (680nm) and blue (450 nm)
what is the chemical structure of chlorophyll?
a porphyrin ring (allow chlorophyll to absorb light) and a phytol tail (anchors in the thylakoid membrane).
how does chlorophyll trap light energy
it converts light energy, photon wavelengths into chemical energy during light reactions
2 main types of accessory pigments
carotenoids and phycobilins
what is the main function of accessory pigments (5 functions)
increase the range of light that a plant can aborb
when they absorb light, they pass off their energy to chlorophyll a, the reaction center of photosynthesis
protect chlorophyll a from photooxidizing
absorb and dissipate excess light energy
increase efficiency of light absorption and photosynthetic rate
absorption spectrum shows what?
how well different wavelengths of light are aborbed by different pigments
what does the action spectrum show
the rate of photosynthesis at different wavelengths, indicating which wavelengths are most effective.
what is the absorption spectrum of chlorophyll (a and b) vs carotenoids
chlorophyll a absorbs in 430 - 660 (blue-violet - red), reflect green
chlorophyll b absorbs in (450 - 650) (torqoise blue - red orange), reflect greeen
carotenoids absorb in the 400 - 500 (absorb blue - green), reflect reds, yellows, oranges
the reaction center is
A specialized pair of chlorophyll a molecules where energy from light (sun), in photons, is converted into electron transport.
it is found in Photosystem I and Photosystem II.
quantum yield refers to
the efficiency of photosynthesis, defined as the number of CO₂ molecules fixed per photon absorbed.
the general concept of a redox reaction involves
transfer of electrons; where oxidation is the loss of electrons, and reduction is the gain.
leo ger
In Photosynthesis: Light energy drives the transfer of electrons from water
to NADP⁺, forming NADPH.
light reactions occur where, and involve what
Occur in the thylakoid membranes (pigment molecules are here), involving electron transport, ATP, and NADPH production.
dark reactions occur where and involve what
in the stroma, using ATP and NADPH to fix CO₂ into glucose.
the Z scheme describes the flow of electrons in which reactions?
what happens in PSII vs PSI?
light reactions
Photosystem II (PSII): Absorbs light, splits water molecules, and releases O₂, drives ATP synthesis
Photosystem I (PSI): Absorbs light and transfers electrons to NADP⁺ to form NADPH.
why is the ETC important in photosynthesis
converts light energy into chemical energy and moves protons across the thylakoid membrane into the lumen
in the calvin cycle, what is carboxylation, reduction, and regeneration
Carboxylation: CO₂ is fixed to RuBP by rubisco.
Reduction: Produces G3P, a precursor for glucose.
Regeneration: RuBP is regenerated from G3P.
what are the roles of Rubp and rubisco
RuBP (Ribulose-1,5-bisphosphate):
The CO₂ acceptor in the Calvin cycle.
Rubisco:
Catalyzes the first step of CO₂ fixation.
what is the role of G3P
A 3-carbon sugar produced in the Calvin cycle, which can be used to form glucose and other carbohydrates.
components of regeneration of Rubp from g3p in calvin cycle
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Regeneration of RuBP:
-
Conversion of G3P:
- G3P (3-carbon) is converted into 5-carbon intermediates.
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Sugar Rearrangements:
- Involves enzymes like aldolase and transketolase.
- Intermediates include ribose-5-phosphate and xylulose-5-phosphate.
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Phosphorylation:
- ATP is used by phosphoribulokinase to phosphorylate ribulose-5-phosphate into RuBP.
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Conversion of G3P:
-
Enzymes Involved:
- Aldolase: Combines sugar phosphates.
- Transketolase: Transfers carbon units between sugars.
- Phosphoribulokinase: Final step, phosphorylates ribulose-5-phosphate to RuBP.
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Energy Requirement:
- ATP is consumed during phosphorylation.
- No NADPH used in this phase.
-
Importance:
- Regenerates RuBP, enabling the continuous fixation of CO₂ in the Calvin cycle.
Know the products and understand the consequences of the dual carboxylation
and oxygenation functions of rubisco
Carboxylation:
CO₂ + RuBP → Two 3-phosphoglycerate (3-PGA) molecules.
Outcome: Leads to the Calvin cycle, producing sugars like G3P.
Oxygenation:
O₂ + RuBP → One 3-phosphoglycerate (3-PGA) + One 2-phosphoglycolate.
Outcome: Initiates photorespiration, which consumes energy and releases CO₂.
Consequences:
Carboxylation:
Efficient CO₂ fixation, leading to sugar production and plant growth.
Oxygenation:
Reduces photosynthetic efficiency by diverting RuBP and consuming ATP and NADPH without producing sugars.
Increases under high O₂/low CO₂ conditions (e.g., drought or high temperatures).
where does photrespiration happen and what are the consequences
Occurs when rubisco fixes O₂ instead of CO₂, leading to the production of 2-phosphoglycolate.
Reduces photosynthetic efficiency.
C4 Metabolism:
Spatially separates CO₂ fixation and the Calvin cycle, reducing photorespiration.
Involves Krantz anatomy.
CAM Metabolism
Temporally separates CO₂ fixation and the Calvin cycle, storing CO₂ at night to minimize water loss.
why can cacti grow in deserts
CAM Photosynthesis:
Crassulacean Acid Metabolism (CAM): Cacti open their stomata at night to take in CO₂, minimizing water loss during the hot daytime.
CO₂ is stored as malic acid in vacuoles and used during the day for photosynthesis when the stomata are closed.
**2. Water Storage:
Succulent Tissues: Cacti have thick, fleshy stems that store large amounts of water, allowing them to survive long periods of drought.
**3. Reduced Leaf Surface:
Spines Instead of Leaves: Spines reduce water loss by limiting transpiration and also provide shade and protection from herbivores.
**4. Efficient Root System:
Shallow and Widespread Roots: Quickly absorb water from light rains.
Deep Roots: Access deeper water reserves during prolonged dry periods.
**5. Thick Cuticle:
A waxy layer on the stem reduces water loss by minimizing evaporation.
**6. Slow Growth:
Reduced metabolic rates help conserve energy and water, allowing cacti to survive in nutrient-poor and water-scarce environments.
main difference between chlorophyll a and chlorohpyll b by functional group
chlorophyll a has a methyl group, chlorophyll b has an aldehyde
chlorophyll is found in the
lumen vs stroma
thylakoid
lumen is fluid inside thylakoid, stroma is fluid in chloroplast
products and reactants of light dependent
h20 is oxidized into O2
NADP+ is reduced into NADPH
ATP is formed via ATP synthase by chemiosmosis via ADP and inorganic phosphate
reactants and products of calvin cycle
ATP turns back into ADP + Pi and drives the calvin cycle, where NADPH is oxidized into NADP+ and then using those electrons, CO2 is able to reduce into glucose
the electron transport chain is in the
thylakoid membrane
krantz anatomy
bundle sheath cells surround vascular bundle (xylem and phloem), and is where calvin cycle takes place
mesophyll cells is where fixation occurs
important for c4 plants bc concentrating c02 in bundle sheaths allow for photosynthesis even in dry conditions when stomata remain closed
