What were the earliest living organisms?
___ manufacture organic nutrients from CO2 and H2S
___ use enrgy from inorganic molecules.
___ use radiant energy to make organic compounds.
___ converts energy from sunlight into chemical energy which is stored in carbohydrates.
In photosynthesis, ___ energy electrons are removed from a donor molecule.
Where does photosynthesis take place in eukaryotes?
Chloroplasts have a double membrane, explain.
- Outer membrane contains porins and is permeable to large molecules
- Inner membrane contains light-absorbinf pigment, electron carriers, and ATP-synthesizing enzymes
The inner membrane of a chloroplsat is folded into flattened sacs called ___, arranged in stack called ___.
Are chloroplasts self-replicating?
Only with their own DNA
What happens during a redox reaction?
The transfer of an electron from water to carbon dioxide.
Photosynthesis oxidizes ___ to oxygen.
What does photosynthesis use to form ATP and NADPH?
What is used to reduce CO2 to a carbohydrate?
ATP and NADPH
What are the 2 stages of photosynthesis?
1. Light-Dependent Reactions (sunlight is absorbed, converting it into ATP and NADPH)
2. Light-Independent Reactions (energy stored in ATP and NADPH is used to produce carbohydrates
What happens when a molecule absorbs photons?
It goes from ground state to excited state.
- - energy in the photon depends on the wavelength of light
- -enrgy required to shift electrons varies for different molecules
Photosynthetic Pigment- Fact Slide
- - molecules that absorb light
- - absorb light of particular wavelengths
- - the alternating single and double bonds along the porphyrin form a cloud = conjugated system
- - conjugated systems absorb energy of a range of wavelengths
___ contains a pophyrin ring that absorbs light and a hydrophobic tail embedding it to the photosynthetic membrane.
Accessory pigments are called ___
What do carotenoids do?
Carotenoids absorb light in the blue-green region of the spectrum.
Each photosynthetic unit has several hundred chlorophyll molecules. Describe the "reaction-center chlorophyll" and the "antenna pigments"
- Reaction-Center Chlorophyll
- - one member of the group
- - transfers electrons to an acceptor
- Antenna Pigments
- - do not participate directly in the conversion of light energy
- - responsible for light absorption
There are 2 large pigment-protein complexes called photosystems that act in a series to raise electrons from water to NADP+ . What are they and what do they do?
1. Photosystem II: boosts electrons from below energy level of water to a midpoint
2. Photosystem I: boosts electrons to a level above NADP+
What is the Z Scheme?
The flow of electrons from H2O to NADP+
How many electrons are required for the formation of O2 from H2O?
Killing Weeds by Inhibiting Electron Transport- Fact Slide
- - common herbicides bind to a core protein of PSII
- - light reactions serve as targets of herbicides
- - some herbicide produce oxygen radicals, which are toxic to the human tissue
The ATP synthase consists of a head (CF1), and a base (CF0). What do each do?
The CF1 heads project outward into the stroma, keeping with the orientation of the proton gradient.
Protons move into the lumen through the CF0 base of the synthase
The movement of protons during photosynthesis does not create a significant change in the membrane potention since other ions are transported simultaneously
What is noncyclic photophosphorylation?
The movement of electrons during the formation of oxygen because ions move in a linear path.
Describe cyclic photophosphorylation
- - carried out by PSI independently of PSII
- - believed to provide additional ATP required for carbohydrate synthesis
What is the first compound that can be identified during carbon dioxide fixation?
Production of a 3-carbon intermediate (3-phosphoglycerate, PGA)
What is another name for the C3 pathway?
What does the Calvin Cycle include?
- - carboxylation of RuBP to form PGA
- - reduction of PGA to glyceraldehyde 3-phosphate (GAP) using NADPH and ATP from reaction
- - regeneration of RuBP
Why is carbon dioxide fixation and the synthesis of carbohydrates "expensive"?
- -conversion of 6 molecules of CO2 to one six-carbon sugar molecules rewuires 12 molecules of NADPH and 18 molecules of ATP
- - expenditure due to CO2 being the most highly oxidized form of carbon
Is redox control light-dependent?
Photorespiration (C3 Plants)- Fact Slide
- - uptake of O2 and release of CO2
- - rubisco also catalyzes the attachment of O2 to RuBP to produce 2-phosphoglycolate
- - glycolate is then transferred tothe peroxisome and leads to release of CO2
- - it accounts for the loss of up to 50% of fixed CO2
- - rate of photorespiration depends on the CO2/O2 ratio
- - glycolate produced during photorespiration is shuttled to the peroxisome
- - peroxisomal enzymes convert glycolate to glyoxylate and then glycine, resulting in the loss of CO2
Carbon Dioxide Fixation and the Synthesis of Carbohydrates (C4 Plants): Fact Slide
- - involves the production of phosphoenolpyruvate (PEP), which then combines with CO2 to produce 4-carbon compounds oxaloacetate or malate
- - in a hot, dry environment C4 plants get enough CO2 for photosynthesis while keeping their stomata partially closed to prevent water loss
- - C4 plants have anatomical adaptation to transport C4 products into the bundle sheath cells, where fixed CO2 can be split from the 4-carbon carrier producing a high CO2 level suitable for fixation by Rubisco
Carbon Dioxide Fixation and the Synthesis of Carbohydrate (CAM Plants)- Fact Slide
- - CAM (crassulacean acid metabolism) plants keep their stomata closed during the day to reduce water loss
- - carry out light reactions and CO2 fixation at different times of the day using the enzyme PEP carboxylase