Review
• Where does photosynthesis occur?
• What are the 2 major stages in
photosynthesis?
Light
dependent
reaction
Reporters:Tiempo, Villamero, Navarro, Goc-ong, Bangay, Pailago
Light Dependent Reaction
• Light reactions or “light dependent
reactions” capture light energy to power
photosynthesis.
• Light reactions occur during the day time.
• They take place in the thylakoids.
• The thylakoid membranes are lined by pigments such as
chlorophyll and carotenoids.
• ATP Synthase is a membrane-bound enzyme that uses
the flow of protons/hydrogen ion (H+) across a
membrane to drive the synthesis of ATP from ADP and
phosphate.
PIGMENTS
ATP SYNTHASE
THYLAKOID
GRANUM
THYLAKOID SPACE
STROMA
ATP SYNTHASE
Photosystem - large complexes of proteins and
pigments (light-absorbing molecules) that are
optimized to harvest light, play a key role in the light
reactions.
Light reaction has two
Photosystem:
1. Photosystem II (PSII)
2. Photosystem 1 (PS1)
• light energy is trapped by chlorophyll to make ATP
(photophosphorylation)
• at the same time water is split into oxygen, hydrogen ions and free
electrons: 2H2O→ 4H+ + O2 + 4e- (photolysis)
• Electrons move through the electron transport chain from
PS II to PS I.
• Energy from these electron (e-) transport Hydrogen ion (H+)
from stroma to thylakoid space.
•
Pigments in Photosystem I use energy from light to convert
NADP to NADPH.
•
ATP is produced from ADP using the energy in the difference
between the sides of the membrane.
•
ATP Synthase is the enzyme that converts ADP to ATP.
Thank You