Chapter 8 Flashcards
Photosynthesis
The conversion of light energy to chemical energy that is stores in sugars or other organic compounds.
Two stages of photosynthesis
- Light reactions in thylakoids: convert solar energy to chemical energy of ATP and NADPH, releases O2.
- Calvin cycle in stroma: fixation of CO2 and reduction of the fixed carbon into carbohydrate.
Photo phosphorylation
The process of generating ATP from ADP and phosphate by means of chemiosmosis using a proton motive force generated across the thylakoid membrane during light reactions.
Light energy is originally converted to what
NADPH and ATP
Carbon fixation
The initial incorporation of carbon from CO2 into an organic compound by an autotrophic organism.
Photons
Discreet particles of light
Substances that absorb visible light
Pigments
Chlorophyll absorbs what
All by green light
3 kinda of pigments in chlorophyll
- Chlorophyll a- key light capturing pigment (blue green)
- Chlorophyll b- this and accessory pigments called carotenoids (broaden spectrum of colour that can be used for photosynthesis)(orange yellow)
Structure of chlorophyll
Phophyrin ring: light absorbing lead with magnesium in Center
CH3 in chlorophyll a, CHO in b
Hydrocarbon tail: interacts with hydrophobic region so fproteins inside thylakoids membranes.
Photo system
A light capturing unit located in the thylakoid membrane of the chloroplast or in the membrane of some prokaryotes consisting of a reaction Center complex surrounded by numerous light harvesting complexes. Two types of photosystems (1 and 2.)
Reaction Center complex
A complex of proteins associated with a special pair of chlorophyll a molecules and primary e-acceptor. This complex trigger the light reactions of photosynthesis. Excited by light energy the park of chlorophyll donates an electron to the primary electron acceptor which passes to an electron in an ETC.
Light harvesting complex
A complex of proteins and pigment molecules (a,b, carotenoids) that Capture light energy and transfer it to the reaction Center pigments in a photosystem.
As soon as the chlorophyll electron is excited to higher state the….
Primary e- acceptor captures it; redox reaction.
PS2
Light capturing unit in thylakoid membrane (membrane of pro.). Acts first!!
Absorbs red part of spectrum
Linear electron flow
A route of electron flow during light reactions that involve both photosymstwms and produces ATP, NADPH and O2.
Thylakoid membrane pumps protons from — to —
Stroma then into thylakoid
APT is synthesized as hydrogen ions diffuse from
The thylakoid space back to the stroma through ATP synthase
Carbs produced by Calvin cycle are
Not glucose but G3P.
For net synthesis of one molecule of G3P Calvin cycle must take place how many time?
3 times, fixing 3 molecules of CO2.
Phase 1 of Calvin cycle
Carbon fixation- incorporates each CO2, one at a time, by attaching it to a 5- carbon sugar (RUBP). The enzyme used to catalyze this is rubisco. Creates two molecules of 3-Phophoglycerbte from each CO2 fixed.
Phase 2 of Calvin cycle
Reduction- each molecule of 3- phophoglycerbte receives an additional phosphate from ATP, becoming 1,3 Biphosphoglycerate. A par of e- donated from NADPH reduces 1,3 bi… which also loses a phosphate group becoming G3P. G3P is a sugar (same as formed in glycolysis)
Phase 3 of Calvin cycle
Regeneration of the CO2 acceptor (RUBP)-carbon skeletons of 5 G3P are rearranged into 3 molecules of RUBP. Uses 3 ATP to do so. RUBP is now ready to receive CO2 again.
Net synthesis of 1 G3P molecule
9 ATP used
6 molecules of NADPH used
C 3 plants
A plant that uses the Calvin cycle for the initial steps that incorporates CO2 into organic material, for,in a three-carbon compound as the first stable intermediate. (Produce less sugar)
Close stomata on hot days
Rice
Photorespiration
A metabolic pathway that consumes O2 and ATP, releases CO2 and decreases photosynthetic output. Occurs on hot days
C4 plants
Calvin cycle is proceeded by light reactions that incorporate a 4- carbon compound. The end product supplies CO2 for the Calvin cycle.
Partially close stomata on hot days
Sugarcane
CAM plants
A plant that uses crassulacean acid metabolism. Carbon dioxide enters the stomata during the night is converted to organic acids, which release CO2 for the Calvin cycle during the day.
Cactus
