Question

The reactions of photosynthesis can be divided into 2 groups. Those that require light are called the (2)__________ __________. Those that can operate in light or darkness are the (3)__________- __________ __________. During the light reactions, molecules called (4)__________ __________ absorb light. The colors that are absorbed the most are (5)__________ and (6)__________. In plant cells, photosynthesis takes place in an organelle called the (7)__________. The light reactions take place on the surface of disk-shaped structures called (8)__________.

Answer 1

The reactions of photosynthesis can be divided into 2 groups.

Those that require light are called the light dependent reaction.

[The first part of photosynthetic reactions require the presence of sunlight. Photons absorbed from the sunlight excite electrons in thylakoid membrane, which is then transported through a series of proteins, PS II, Cytochrome complex, PS I and ATP synthase in thylakoid membrane. This leads to activation of ATP synthase enzyme and production of ATP, which would be required in the light independent reactions of photosynthesis.]

Those that can operate in light or darkness are the light-independent reaction.

[Dark reactions or light-independent reactions does not occur in absence of light necessarily. Instead, presence or absence of light is not a factor for these reactions. In photosynthesis, light is only required for the photosynthetic electron transport chain that leads to the production of ATP, as mentioned above.]

During the light reactions, molecules called photosynthetic pigments absorb light.

[Photosynthetic pigments are present in the reaction center of Photosystem II (PS II), embedded in the thylakoid membrane. They are responsible for absorbing particular wavelengths of light while reflecting others. Photosynthetic pigments are thus responsible for absorbing photons in PS II and exciting electrons which starts the electron transport chain.]

The colors that are absorbed the most are violet and red.

[Most abundant photosynthetic pigment is chlorophyll a. It mainly absorbs light from the extreme ends of the visible spectrum, i.e., violet, blue and red, while reflecting green light. That is why most photosynthetic plants have green colored leaves.]

In plant cells, photosynthesis takes place in an organelle called the chloroplast.

[Photosynthesis takes place in the thylakoid compartments present inside the double membrane bound chloroplast organelle present in cells of plants.]

The light reactions take place on the surface of disk-shaped structures called thylakoids.

[Inside the chloroplast there is are disk shaped structure called thylakoids present in stacks called grana. Light reaction occurs on the membrane of the disk shaped thylakoid. Photosynthetic pigments, as well as the protein complexes for electron transport chain are situated on thylakoid membrane.]