Light-dependent reactions (light reactions) 2.

Chapter 22 ("Electron Transport and Oxidative Phosphorylation") in Voet & Voet (3rd Edition) is one of the most important chapters in the entire text (at least in my opinion) and it would help to reread it as you look at the light reaction of photosynthesis in more detail over the next two lectures.

light dependent reactions and light independent or dark reactions.

Light-independent reactions .Dark Reactions of Photosynthesis: The Calvin-Benson Cycle.

The light reaction takes place in the thylakoid discs.

We'll look at a simpler example of photosynthesis first, and use it as an introduction to photosynthesis in plants and cyanobacteria (blue-green algae). Although the primary reactions of photosynthesis take place at "photosynthetic reaction centers," the first level of interaction of light with an organism that carries out photosynthesis is at an assembly of chlorophyll molecules that "harvest" light (the "light-harvesting complex"). Such an assembly results in a greater chance that photons will be captured and, because of the strategic arrangement of the individual chlorophyll and other accessory light-absorbing molecules, the transfer of energy to the photosynthetic reaction center is very fast (-10 s) and very efficient (>90%).

PHOTOSYNTHESIS Light and Dark Reaction song song.

Both the LHC and the reaction centers are membrane bound structures but there are no chloroplasts in the purple photosynthetic bacteria. The electron transfer processes occur within the cell membrane and the overall process is a cyclic one (i.e., there is no net oxidation-reduction). Protons are transferred across the membrane, from the cytoplasmic side to the outside, establishing a proton gradient whose dissipation drives ATP synthesis. A similar situation holds for the cyanobacteria and plants, but in these organisms, the process occurs in chloroplasts and the overall reaction is not a cyclic one.

The light reactions can be split into the following specific steps: 1.

high light intensity increases the rate of photosynthesis

Light reactions need light to produce organic energy molecules (ATP and NADPH). They are initiated by colored pigments, mainly green colored chlorophylls.

Photosynthesis - Light-Dependent Reactions

It turns out that the overall reaction of photosynthesis takes place in two steps. In the first step, the oxygen in water is oxidized by the light energy:

Steps of the Light Reaction ATP – Used in the dark reaction of photosynthesis.

Light independent reaction (Calvin cycle) animation

Reaction (2) is known as the "light reaction" and reaction (3) is known as the "dark reaction" but both can take place in the light. However, (2) is light-dependent, whereas (3) is not.

Apr 27, 2016 · Photosynthesis is a process in which light energy is and the dark reactions.

Photosynthesis Light reaction, Calvin cycle ..

The first step in photosynthesis is the interaction of light with chlorophyll molecules. The chemical structures of the various chlorophyll molecules are based upon the cyclic tetrapyrrole that is also seen in the heme group of globins and cytochromes. Various modifications of this group, namely ring saturation characteristics and substitutions on the rings provide a series of pigment molecules that, as a group, absorb effectively over the wavelength range of 400 nm - 700 nm, the spectrum of . It is the high degree of conjugation of these molecules that makes them so efficient as absorbers of visible light.

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

Photosynthesis: Light Reactions

During photosynthesis, a process that occurs in plants and in cyanobacteria and also in purple photosynthetic bacteria, light energy is converted into chemical energy. The overall process is described by the chemical equation: