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Writer's picturePlantHouse Enterprise

Plant Physiology Lesson 3A Photosynthesis Machinery: Light Dependent & Independent Reactions


Delivered on: 4 APRIL 2022


This video provides a comprehensive overview of the intricate machinery behind photosynthesis, the process by which plants convert light energy into chemical energy. 🌿 We'll explore the two main stages of photosynthesis: the light-dependent reactions and the light-independent reactions (Calvin cycle).


What you'll learn:

  • Chloroplast Structure:  We'll review the structure of chloroplasts, the organelles where photosynthesis takes place, including thylakoid membranes, grana, and stroma.

  • Light-Dependent Reactions:  Explore the light-dependent reactions that occur in the thylakoid membranes, including the roles of photosystems, chlorophyll, and electron transport chains in capturing light energy and producing ATP and NADPH.

  • Photosystem II and Photolysis:  Understand the role of Photosystem II in splitting water molecules (photolysis) to release oxygen and generate electrons for the electron transport chain.

  • Photosystem I and NADPH Production:  Learn how Photosystem I utilizes light energy to reduce NADP+ to NADPH, a crucial reducing agent for the Calvin cycle.

  • Chemiosmosis and ATP Synthesis:  Discover how the movement of electrons through the electron transport chain creates a proton gradient that drives ATP synthesis via ATP synthase.

  • Calvin Cycle:  Explore the Calvin cycle, the light-independent reactions that occur in the stroma, where carbon dioxide is fixed and converted into sugars using ATP and NADPH.

  • Phases of the Calvin Cycle:  We'll break down the three phases of the Calvin cycle: carbon fixation, reduction, and regeneration.


Video Timestamps:

1:19 Briefing the photosynthesis

2:00 Advices from dr Nazmin

3:37 Introduction of photosynthesis machinery

5:46 Types of plants or photosynthetic organisms

7:03 Light and wavelength (physics)

10:03 Basic ingredients of photosynthesis

11:12 Why are plants green?

11:59 wide range of greens

12:34 Chloroplasts

15:16 Leaf is transparent?

16:05 The location and structure of chloroplasts

20:10 Where is photosynthesis occur?

23:30 Photosynthesis simplify

25:47 Surface of thylakoid membrane

26:43 Chloroplast pigments

29:26 Leaf chromatography

32:04 Paper Leaf Chromatography

33:35 Chlorophyll a & b (photosynthesis)

35:54 different pigments absorb light differently

38:07 Reaction in photosynthesis

38:37 An overview of photosynthesis

39:00 Light reaction

43:21 ATP and NADPH was used by Calvin Cycle to produce sugar

44:38 The Calvin Cycle (3 phases)

45:47 the light-dependent reaction

47:26 Noncyclic Photophosphorylation (z-scheme)

49:10 Two types of photosystem

49:21 Where O2 comes from?

50:49 Terminology

52:11 why does it called P680?

58:03 The electron chain

59:22Photosystem I (P700)

1:00:17 How ATP got produced?

1:03:20 Chemiosmosis process

1:05:44 ATP Synthase

1:07:19 Photo reaction

1:07:59 Summary – Light Dependent Reactions

1:08:39 Light Independent Reaction (Synthesis)

1:09:36 The Calvin Cycle (Fixation)

1:13:07 The Calvin Cycle (Reduction)

1:14:00 Regeneration

1:15:36 Steps of Photosynthesis

1:16:29 Summary of Light independent reactions

1:19:53 QnA session


Overview of Photosynthesis

The exergonic light-dependent reactions of photosynthesis convert light energy into chemical energy, producing ATP and NADPH. These reactions occur in the thylakoids of the chloroplasts. The products of the light-dependent reactions, ATP and NADPH, are both required for the endergonic light-independent reactions.


The endergonic light-independent reactions of photosynthesis use the ATP and NADPH synthesized during the exergonic light-dependent reactions to provide the energy for the synthesis of glucose and other organic molecules from inorganic carbon dioxide and water. This is done by "fixing" carbon atoms from CO2 to the carbon skeletons of existing organic molecules. These reactions occur in the stroma of the chloroplasts.


Keywords: Photosynthesis, chloroplast, light reactions, Calvin cycle, photosystem, chlorophyll, electron transport chain, ATP synthesis, NADPH, carbon fixation, photolysis, plant physiology.


Attribution 4.0 International — CC BY 4.0 - Creative Commons

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