Light-dependent reaction of photosynthesis at the thylakoid membrane

Cyclic photophosphorylation involves only Photosystem I and generates ATP but not NADPH.

Light Reactions of Photosynthesis - SERC

However, although light-independent reactions are, by convention, also called dark reactions, they are not independent of the need of light, for they are driven by ATP and NADPH, products of light.

These four complexes work together to ultimately create the products ATP and NADPH.

Light-dependent reactions of photosynthesis - BioTopics

A byproduct of this chemical reaction is oxygen, which is released through holes in the leaf called stomates.

The light-dependent reactions, or photoreduction, is the first stage of photosynthesis, the process by which plants capture and store energy from sunlight.

The energy that is used to make these reaction occur is from the ATP and NADPH.

Dark reactions make use of these organic energy molecules (ATP and NADPH). This reaction cycle is also called Calvin Benison Cycle, and it occurs in the stroma. ATP provides the energy while NADPH provides the electrons required to fix the CO2 (carbon dioxide) into carbohydrates.







To experimentally determine the effect of lightintensity on the rate of the light-dependent reactions of photosynthesis.


3 are called the light reactions of photosynthesis

Summary Stage I: Light-Dependent Reactions.
The light-dependent reactions transform light energy into chemical energy which is trapped and carried by ATP and NADPH to the Calvin Cycle.

The light-dependent reactions require chlorophyll and occur in the thylakoid membranes of the grana of the chloroplast.


Light energy is also used to split water (Photolysis of water) into:



H2O -----> 2H+ + 2e- + 1/2 O2 This reaction produces oxygen and provides electrons and Hydrogen for the reduction of NADP to NADPH (NADP gains H+ and electrons; the water is oxidized because it loses the H+and e-)

The light reactions remove electrons from excited chlorophyll molecules in both Photosystem I and Photosystem II and pass the higher energy electrons along an electron transport chain, releasing energy to make ATP (from ADP and P), or transferring the electrons to NADP.


The light reactions must occur several times to produce enough ATP and NADPH to "run" the Calvin cycle Stage II: Calvin Cycle or C-3 Photosynthesis
(Sometimes called the Dark Reactions)

Six molecules of Carbon dioxide each combine with a 6 molecules of a 5-carbon sugar (Ribulose bisphosphate) and undergo a reduction to form 3-carbon molecules (Glyceraldehyde 3 Phosphate or G3P).
Ten of the 12 molecules of G3P are used to regenerate more ribulose bisphosphate to keep the cycle going.
Two of the 12 G3P are converted to the carbohydrate, glucose.


These photosynthetic reactions do not use light energy for the energy source.

Light-dependent reactions - Wikipedia

In this process, light energy is converted into chemical energy, in the form of the energy-carrying molecules ATP(Adenosine triphosphate) and NADPH(Nicotinamide adenine dinucleotide phosphate).

Photosynthesis Flashcards | Quizlet

Nevertheless, the Calvin cycle in most plants occurs during daylight, for only then can the fight reactions regenerate the NADPH and ATP spent in the reduction Of C02 to sugar.

Biology Quiz Ch.10 Flashcards | Quizlet

In respiration energy is released fromsugars when electrons associated with hydrogen are transported to oxygen (theelectron acceptor), and water is formed as a byproduct. The mitochondriause the energy released in this oxidation in order to synthesize ATP. Inphotosynthesis, the electron flow is reversed, the water is split (not formed),and the electrons are transferred from the water to CO2 and in theprocess the energy is used to reduce the CO2 into sugar. Inrespiration the energy yield is 686 kcal per mole of glucose oxidized to CO2,while photosynthesis requires 686 kcal of energy to boost the electrons from thewater to their high-energy perches in the reduced sugar -- light provides thisenergy.