Chapter 8-Photosynthesis Flashcards
Anoxygenic photosynthesis
Does NOT produce oxygen
Oxygenic Photosynthesis
Produces oxygen
- Carried out by
1) Cyanobacteria
2) 7 groups of algae
3) All land plants
Photosynthesis 3 Stages
1) Capturing energy from sunlight
2) Using energy to make ATP and to reduce the compound NADP to NADPH
3) Using the ATP and NADPH to power the synthesis of organic molecule from CO2 in the air
Carbon fixation
- Organic molecule from CO2 in the air
- These reactions may occur in the present or absence of light
Thylakoid membrane
The internal membrane of chloroplast
Grana
Flattened sacs, stacked on one another
Chlorophyll
Photosynthetic pigments for capturing light energy along with the machinery to make ATP
Stroma lamella
Connections between Grana
Storma
Semiliquid substance surrounding the thylakoids membrane
Photosystems
Clustered photosynthetic pigments, which show distinct organization w/in the thylakoids
What does a pigment molecule do?
- Captures light and passes it’s energy from one’ll exile to another until it reaches chlorophyll
Baptista
Demonstrated that the substances of the plant was not produced ONLY from the soil
Priestly
Living vegetation adds something to the air
Ingen- Housz
Plants carry out a process that uses sunlight to split CO2 into C and O2
F.F Blackman
1) Photosynthesis is in fact multistage process
2) Light versus dark reactions
3) Enzymes involved
C.B van Neil
- Purple sulfur bacteria do not release O2 but accumulate sulfur
- Proposed general formula for photosynthesis
Robin Hill
- Light energy could be harvested and used in a reduction reaction
Pigment
Molecules that absorb light energy in the visible range
Photon
- Particle of light
- Acts as a discrete bundle of energy
Photon energy is INVERSELY proportional to what?
Wavelength of light
- Short wavelength= ⬆️ energy photons
- Long wavelength= ⬇️ energy photons
Photoelectric effect
Removal of an electron from a molecule of light
Absorption Spectrum
The range and efficiency of photons it is capable of absorbing
When a photon strikes a molecule, it’s energy is either?
1) Lost as heat
2) Absorbed by the electrons
2 General Pigments in Photosynthesis:
1) Chlorophyll
2) Carotenoids
Chlorophyll a
- Main photosynthetic pigment
- ONLY pigment that can directly concerned light energy to CHEMICAL ENERGY
- Absorbs: violet- blue and red light
Chlorophyll b
- Accessory pigments or secondary pigment
- Absorbs photons chlorophyll a can not
Accessory Pigment
Complements and adds to the light absorption of chlorophyll a
What kind of ring does a pigment contain?
Porphyrin Ring
Prophyrin Ring
- Complex ring structure with alternating double and single bonds
- Mg center atom
Action Spectrum
- Relative effectiveness of different wavelengths of light in promoting photosynthesis
- Corresponds to the absorption spectrum for chlorophylls
Chlorophyll has way better _________ that other pigments
Photoefficiency
Carotenoids
- Consist of carbon rings linked to chains with alternating single and double bonds
- Can absorb photons with a wide range of energies
- Act as general-purpose antioxidants to lessen damage
Phycobiloprotiens
- Helps plants in low- light ocean areas
What do experiment on plants show?
The output of photosynthesis increases liberally at low light intensities, but becomes Saturated at high intensities
Photosystems
Network of chlorophyll a molecules, accessory pigments, and associated proteins held w/in a protein matrix on the surface of the photosynthetic membrane
Photosystems 2 Components:
1) Atenna Complex
2) The Reaction Center
Antenna Complex
- Light- harvesting center
- Captures photons from sunlight and channel then to the reaction center chlorophylls
- Consists of a web of chlorophyll molecules linked together and held tightly in the thylakoids membranes by a matrix of proteins
The Reaction Center
- Transmembrane protein-pigment complex
- 1 or more chlorophyll a molecules
- When a chlorophyll in the reaction center absorbs a photon of light an electron is excited to a higher energy lever
- Passes excited electrons to an electron acceptor, reducing it
Light Dependent Reaction’s 4 Stages:
1) Primary photoevent
2) Charge separation
3) Electron transport
4) Chemiosmosis
1) Primary Photoevent
- Photon of light is captured by a pigment
2) Charge Seperation
- Energy is transferred to the reaction center
- An excited electron is transferred to an acceptor molecule
3) Electron Transport
- Excited electrons are shuttled along a serious if electron carrier to reduce NADP
- Create a protein gradient
Chemiosmosis
ATP synthase produces ATP
Cyclic Phosphorylation
- Generates ATP via electron transport
- Anoxygenic photosynthesis
- Generated a proton gradient for ATP Synthesis
Enhancement Effect
One Photosystem absorbs preferentially in the red, the other in the far-red
Noncyclic Photophosphorylation
-The path of the electron is NOT a circle
Photosystem 2
- Resembles the reaction center of purple bacteria
- Consists of 10 transmembrane protein subunits
- P680 chlorophyll
- 4 Mg atoms
- This process requires the reaction to absorb 4 photons to complete the oxidation of 2 H2O molecules➡️ creating 1 O2
Primary electron acceptor
Plastiquinone
b6- f complex
Proton pump embedded w/in the thylakoids membrane accepts electron pair (inbetween P2 and P1)
Plastocyanin
Carriers the electron pair to Photosystem 1
Photosystem 1
- Consist of a core transmembrane complex consisting of 12-14 protein subunits
- P700
- Photons boost the electrons to a very high energy level
- Electrons passed to➡️ Ferredoxin
- 2 molecules of reduced Ferredoxin are then used to form NADPH
ATP Synthase
- The chloroplast has ATP synthase enzymes in the thylakoids membrane that form a channel, allowing protons to cross back out into the stroma
Where is Photosystem 2 found?
GRANA
Where is Photosystem 1 found?
Stroma Lamella
To build carbohydrates:
1) Energy➡️ ATP drives the endergonic reactions
2) Reduction Potential➡️ NADH provides a source of protons and the energetic electrons needed to bind then to carbon atoms
Calvin Cycle
The cycle of reactions that allow carbon fixation
- Another name➡️ C3 Photosynthesis
Calvin Cycle 3 Phases
1) Carbon fixation
2) Reduction
3) Regeneration of RuBP
1) Carbon Fixation
RuBP + CO2 ➡️ PGA
2) Reduction
PGA is reduced to G3P
3) Regeneration of RuBP
- PGA is used to regenerate RuBP
- 3 turns incorporate enough to price a new G3P
- 6 turns incorporate enough carbon for 1 glucose
How many carbons undergo a cycle?
36 carbons create 2 molecules of G3P
Photorespiration
O2 is incorporated into RuBP which undergoes additional reactions that actually release CO2
The stroma does what when there are high temperatures?
The stroma closes to conserve water
- CO2 doesn’t come in and O2 doesn’t go out
- When Photorespiration takes place
C3 plants
Fix carbon only using C3 photosynthesis
C4 plants
Oxaloacetate➡️ Malate which moves into bundle sheath cells➡️ Decarboxyilized back into puyruvate➡️ Puruvate goes back into mesophyll cell
- Spacial Resolution
CAM Plants
- Stomata open during the night and close during the day
- Fix CO2 using PEP carboxylate during the night and store in a value
Give an example of a C4 plant?
Corn, grasses, sugarcane
Give examples of CAM plants?
- Water-storing plants➡️ Cacti and pineapples
