Chapter 7- Photosynthesis

Photosynthesis

A metabolic pathway that is the process of using sunlight to make glucose, a two stage process
 Light-dependent Reactions (LDR)
▪ Requires Light
▪ Produces ATP and NADPH
▪ Occurs in the thylakoid membranes
 Light-independent Reactions (LIR)
▪ Uses ATP and NADPH as energy
▪ Produces glucose
▪ Occurs in the stroma

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Term	Definition
Photosynthesis	A metabolic pathway that is the process of using sunlight to make glucose, a two stage process  Light-dependent Reactions (LDR) ▪ Requires Light ▪ Produces ATP and NADPH ▪ Occurs in the thylakoid membranes  Light-independent Reactions (LIR) ▪ Uses ATP and NADPH as energy ▪ Produces glucose ▪ Occurs in the stroma
Summary reaction of photosynthesis
Chloroplast	A plastid that has the functions of photosynthesis and storage
Parts of chloroplast	Thylakoid, granum(stack of t), outer and inner membrane, stroma, stroma thylakoids, and thylakoid space
Thylakoid	Part of chloroplast in the thylakoid membrane system, light-dependent reactions occur here
Stroma	Part of chloroplast, Photosystem 1 occurs mostly here, Light-independent reactions occur here, the final step of ETC2 occurs here, ATP-synthase generates ATP here, Calving Cycle occurs here
Light-dependent reaction(LDR)	Requires light, produces ATP and NADPH, and occurs in the thylakoid membrane
Light-independent reaction(LIR)	Uses ATP and NADPH as energy, produces glucose, and occurs in the stroma
Electromagnetic spectrum	It is the only part our eyes can detect Ranges from 380 nm (violet) to 750 nm (far-red)
Wavelength
Photon	Particles of light that have zero mass, photon energy is inversely related to wavelength
Pigments (photopigments)	Substances that absorb light, pigment color is determined by wavelengths that are not absorbed, unabsorbed wavelengths are reflected or transmitted
Ground state	The lowest energy state
Fluorescence	Release of a less energetic photon
Chlorophylls	Chl-a, b, c, and Bacteriochlorophylls
Chl-a	Primary pigment in plants
Chl-b	Accessory pigment in plants
Chl-c	Accessory pigment in algae
Bacteriochlorophylls	Pigment in bacteria
Phycobilins	Cyanobacteria & red algae
Carotenoids	Accessory pigments(Carotenes (e.g., β-carotene, lycopene, Xanthophylls), Also function as anti-oxidants
Carotenes	B-carotene, lycopene
Absorption spectrum	The wavelengths absorbed by a pigment
Action spectrum	The wavelengths used by a specific process
Photosystem complexes	A large protein-pigment supercomplex
Reaction center	A special pair of chl-a molecules, plus associated proteins, enzymes, and ETC
Antenna complexes	Surrounds the reaction center, pigment-binding proteins hold pigments in place
Light-harvesting complexes(Lhc)	External to other complexes, smaller and lack a reaction center
Photosystem I (P700 reaction center)	Found mostly in stroma thylakoids P700 reaction center Lacks O-evolving center
Photosystem II (P680 reaction center)	Found mostly in grana thylakoids P680 reaction center Has O-evolving center
Photolysis	The splitting of water by photosystem 2
Oxygen-evolving (water-splitting) Complex	Splits water molecules generating electrons, H+, and oxygen (O2)
Non-cyclic photophosphorylation	A light-dependent reaction
Cyclic photophosphorylation	Light-independent Reaction that requires ATP and NADPH ▪ More ATP is used than NADPH ▪ This results in a build-up of excess NADPH
Electron Transport Chain (ETC1 & ETC2)	Occur in non-cyclic photophosphorylation,
Pheophytin	The primary electron acceptor (PEA) for PSII
Plastoquinone (PQA & PQB)	A mobile, lipid-soluble electron carrier molecule embedded within the thylakoid membrane of chloroplasts
Plastoquinol (PQBH2)	The fully reduced, proton-rich form of plastoquinone
Plastocyanin (PC)	A small, water-soluble, copper-containing protein located on the lumenal side of the thylakoid membrane
Cytochrome Complex	A massive, multi-subunit integral membrane protein complex embedded within the thylakoid membrane
A1 (phylloquinone)	A tightly bound, lipid-soluble electron carrier molecule located within the core of Photosystem I (PSI)
Fe-S Protein Complex	An array of 3 iron-sulfur proteins bound to PSI
Ferredoxin (Fd)	Allows for chemiosmosis to continue producing ATP
FNR (ferredoxin-NADP+ reductase)	The final enzyme in the electron transport chain of light-dependent photosynthetic reactions
NADPH/NADP+	Form the primary coenzyme system responsible for transferring reducing power in anabolic (building) biological reactions
ATP-synthase	Molecular rotary motor embedded in the thylakoid membrane that synthesizes ATP from ADP and inorganic phosphate
Calvin Cycle	The term for light-independent reactions that converts CO2 into G3P and has three stages, Carbon Fixation Stage, Reduction Stage, and Regeneration Stage. This cycle occurs in the stroma of the chloroplast
Carbon Fixation Stage	The first stage in the Calvin Cycle where CO2 is added to RuBP and Two molecules of PGA (3-phosphoglycerate) are formed
Ribulose 1,5-bisphosphate (RuBP)	A 5-carbon sugar
Rubisco (RuBP carboxylase/oxygenase)	Catalyzes RuBP
3-Phosphoglycerate (PGA)	A three-carbon organic molecule that serves as the crucial first stable intermediate product of carbon fixation in the Calvin Cycle
1,3-bisphosphoglycerate (1,3-PGA)	Serves as the short-lived structural bridge inside the Calvin Cycle that connects the carbon fixation stage to the sugar reduction stage.
Photorespiration	(also known as the oxidative photosynthetic carbon cycle) is a wasteful metabolic pathway that occurs in plants when the enzyme Rubisco accidentally fixes molecular oxygen instead of carbon dioxide
Phosphoglycolate	A 2-C molecule, used in photorespiration
C3 Photosynthesis	The metabolic pathway for carbon fixation,l not very effective in harsh weathers
C4 Photosynthesis	An advanced evolutionary upgrade to the standard C3 pathway designed to completely bypass the wasteful process of photorespiration
PEP-carboxylase	Binds CO2 to PEP to make oxaloacetate, occurs during C4 Photosynthesis
Kranz Anatomy	C4 plants often exhibit Kranz anatomy ▪ Spatial separation of C4 pathway and Calvin Cycle  This has evolved independently many times
Bundle Sheath Cells	Specialized plant cells that form a tightly packed protective layer around the vascular bundles (the phloem and xylem veins) inside a leaf
Mesophyll Cells	Specialized, chlorophyll-rich parenchyma cells located in the interior of a plant leaf, positioned between the upper and lower epidermal layers
Crassulacean Acid Metabolism (CAM)	A photosynthetic pathway in some succulents
Stomata	open at night and close during the day in CAM
How many ATP are required to make one glucose molecule by photosynthesis?	18
Cyclic photophosphorylation allows for the continued production of which molecule?	ATP
How many carbon dioxide molecules must pass through the Calvin cycle to make one glucose molecule?	3
For each surplus G3P molecule made by the Calvin cycle, how many more ATP are used than NADPH?	3
C4 plants increase the efficiency of photosynthesis by doing what?	Actively moving carbon dioxide into the bundle-sheath cells
Where does the Calvin Cycle occur	In the Stroma of the Chloroplast
How many G3P molecules are required to reform the RuBP used in the Calvin cycle?	5
Cyclic photophosphorylation allows for the continued production of which molecule?	ATP
A plant with Kranz anatomy would most likely be doing what?	C4 photosynthesis