Transcript Photosynthesis - THESTUDENTSCHOOL

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
• 6CO2 (g) + 6H2O (l) + Energy  C6H12O6 (s) + 6O2 (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, CO2 and water
• Water enters through the roots, travels up to the
leaves
• CO2 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 http://www.buzzle.com/articles/photosynthesisdiagram.html
Leaf cross section
Leaves and Leaf Anatomy - EnchantedLearning.com. (n.d.). Retrieved November 24, 2014, from
http://www.enchantedlearning.com/subjects/plants/leaf/
Chloroplast
Shmoop Editorial Team. (2008, November 11). The Light-Dependent and Light-Independent Reactions - Shmoop Biology. Retrieved
November 24, 2014, from http://www.shmoop.com/photosynthesis/light-independent-reactions.html
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 http://www.shmoop.com/photosynthesis/inputs-architecture.html
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 http://biology4isc.weebly.com/3-photosynthesis-andtransport-of-solutes.html
Noncyclic Photophosphorylation
Photosynthesis and transport of solutes. (n.d.). Retrieved November 24, 2014, from http://biology4isc.weebly.com/3-photosynthesis-andtransport-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 http://kensieandhuntersproject.blogspot.co.uk/2013/05/describe-processof-chemiosmosis-in.html
Cyclic Phosphorylation
Photosynthesis and transport of solutes. (n.d.). Retrieved November 24, 2014, from http://biology4isc.weebly.com/3-photosynthesis-andtransport-of-solutes.html
Noncyclic Photophosphorylation
Photosynthesis and transport of solutes. (n.d.). Retrieved November 24, 2014, from http://biology4isc.weebly.com/3-photosynthesis-andtransport-of-solutes.html
Cyclic and Noncyclic
Photosynthesis and transport of solutes. (n.d.). Retrieved November 24, 2014, from http://biology4isc.weebly.com/3-photosynthesis-andtransport-of-solutes.html
References
Leaves and Leaf Anatomy - EnchantedLearning.com. (n.d.). Retrieved November 24, 2014, from
http://www.enchantedlearning.com/subjects/plants/leaf/
K, S. (n.d.). Photosynthesis Diagram. Retrieved November 24, 2014, from
http://www.buzzle.com/articles/photosynthesis-diagram.html
Photosynthesis and transport of solutes. (n.d.). Retrieved November 24, 2014, from
http://biology4isc.weebly.com/3-photosynthesis-and-transport-of-solutes.html
Photosynthesis. (n.d.). Retrieved November 24, 2014, from
http://kensieandhuntersproject.blogspot.co.uk/2013/05/describe-process-of-chemiosmosis-in.html
Shmoop Editorial Team. (2008, November 11). Inputs and Architecture of Photosynthesis - Shmoop
Biology. Retrieved November 24, 2014, from http://www.shmoop.com/photosynthesis/inputsarchitecture.html
Shmoop Editorial Team. (2008, November 11). The Light-Dependent and Light-Independent Reactions Shmoop Biology. Retrieved November 24, 2014, from http://www.shmoop.com/photosynthesis/lightindependent-reactions.html