Photosynthesis Light-Dependent Reaction By: Naweed Zamani

What is Photosynthesis? The process of transforming radiant energy of sunlight into the chemical energy of high-energy compounds Equation of Photosynthesis 6CO 2 (g) + 6H 2 O (l) + Energy  C 6 H 12 O 6 (s) + 6O 2 (g) Main reactions that make up Photosynthesis are – Light-Dependent – Light-Independent

Light-Dependent Reaction The main function of this reaction is to provide a source of ATP and reduced NADP for the dark side reaction Involves light energy, CO 2 and water Water enters through the roots, travels up to the leaves CO 2 enters through openings in the leaf called Stomata Both diffuse into the cells of the leaves which then enter the chloroplasts Light is absorbed by molecules inside the Thylakoids of chloroplasts

Plant diagram K, S. (n.d.). Photosynthesis Diagram. Retrieved November 24, 2014, from diagram.html

Leaf cross section Leaves and Leaf Anatomy - EnchantedLearning.com. (n.d.). Retrieved November 24, 2014, from

Chloroplast Shmoop Editorial Team. (2008, November 11). The Light-Dependent and Light-Independent Reactions - Shmoop Biology. Retrieved November 24, 2014, from

Visible Light Spectrum The visible spectrum is the portion of the electromagnetic spectrum can be seen by human eye. The colours are Red, Orange, Yellow, Green, Blue, Indigo and Violet Each wavelength (color) of visible light varies in energy – Long wavelength = small amount of energy – Short wavelength = large amount of energy

Electromagnetic Spectrum Shmoop Editorial Team. (2008, November 11). Inputs and Architecture of Photosynthesis - Shmoop Biology. Retrieved November 24, 2014, from

Absorption of Light Within thylakoid membrane are pigments which absorb wavelengths of visible light Chlorophyll is the main type of photosynthetic pigments in plants and it is green, it does not absorb green wavelengths of light thus it will reflect it A reason why leaves appear to be green is due to the dominance of the green chlorophyll pigment which reflects green light Chlorophyll a is the main pigment, chlorophyll b and carotenoids are accessory pigments. accessory pigments help broaden the absorption spectrum

Photosystems There are two Photosystems – Photosystem II 680 – Photosystem I P700 Made up of clusters of chlorophyll, accessory pigments embedded in the thylakoid membrane Protein based complexes Photons are absorbed when shown onto leaf and then passed on through antenna complexes until it reaches the reaction centre This causes the electrons of the reaction centre to become excited then leave the centre and attach itself to the electron carrier

Photosystem Photosynthesis and transport of solutes. (n.d.). Retrieved November 24, 2014, from transport-of-solutes.html

Noncyclic Photophosphorylation Photosynthesis and transport of solutes. (n.d.). Retrieved November 24, 2014, from transport-of-solutes.html

Noncyclic Photophosphorylation Step 1: Light is absorbed in Photosystem II then transferred to the reaction center, electron becomes excited then attaches to electron acceptor Reaction center grabs a pair of electrons from water to stabilize Oxygen is produced when two water molecules lose their pairs of electrons Process keeps on repeating each time an electron becomes excited and leaves the reaction center

Noncyclic Photophosphorylation Step 2: electron acceptor passes the electrons through a electron transport chain, energy is released as passed along Protein complex B6-F uses this energy to pump hydrogen ions from stroma into the thylakoid space creating a proton gradient to aid in ATP creation

Noncyclic Photophosphorylation Step 3: light energy is also shown into photosystem II and undergoes the same process of photosystem I. The electron of the P700 reaction center is energized then attaches itself to an electron acceptor The P700 molecule’s lost electrons are then replaced by the electron from the P680 molecule which was passed on through the electron transport chain until it reached photosystem II, thus becoming stable again An electron carrier carries the electrons to NADP reductase NADP is then reduced into NADPH and then used for the Light-Independent reaction

Making ATP by Chemiosmosis The proton gradient in the Thylakoid space is created by positively charged hydrogen ions pumped by the B6-F complex Hydrogen ions cannot diffuse out of the space due to it being to large to diffuse through membrane Hydrogen ions travel through ATP synthase, its energy is used to synthesis ADP-> ATP

Chemiosmosis Photosynthesis. (n.d.). Retrieved November 24, 2014, from of-chemiosmosis-in.html

Cyclic Phosphorylation Photosynthesis and transport of solutes. (n.d.). Retrieved November 24, 2014, from transport-of-solutes.html

Noncyclic Photophosphorylation Photosynthesis and transport of solutes. (n.d.). Retrieved November 24, 2014, from transport-of-solutes.html

Cyclic and Noncyclic Photosynthesis and transport of solutes. (n.d.). Retrieved November 24, 2014, from transport-of-solutes.html

References Leaves and Leaf Anatomy - EnchantedLearning.com. (n.d.). Retrieved November 24, 2014, from K, S. (n.d.). Photosynthesis Diagram. Retrieved November 24, 2014, from Photosynthesis and transport of solutes. (n.d.). Retrieved November 24, 2014, from Photosynthesis. (n.d.). Retrieved November 24, 2014, from Shmoop Editorial Team. (2008, November 11). Inputs and Architecture of Photosynthesis - Shmoop Biology. Retrieved November 24, 2014, from architecture.htmlhttp:// architecture.html Shmoop Editorial Team. (2008, November 11). The Light-Dependent and Light-Independent Reactions - Shmoop Biology. Retrieved November 24, 2014, from independent-reactions.htmlhttp:// independent-reactions.html