Question

Which equation best represents photosynthesis in plants?
a. Carbon dioxide + water $\longrightarrow$ starch + oxygen
b. Carbon dioxide + water $\longrightarrow$ glucose + oxygen
c. Glucose + oxygen $\longrightarrow$ carbon dioxide + water
d. Carbon dioxide + glucose $\longrightarrow$ starch + oxygen
e. Light + carbon dioxide $\longrightarrow$ glucose + oxygen

Answer 1

Hint: The end product of photosynthesis is a monosaccharide. It is also known as dextrose and grape sugar. One of the raw materials used is a greenhouse gas.

Complete answer:
Photosynthesis is the synthesis of complex organic substances by plants in the presence of sunlight using $CO_2$ and $H_2O$ from the surrounding environment.

The reaction occurring in photosynthesis can be given as follows:
${ 6CO }_{ 2 }+{ 12H }_{ 2 }{ O\quad \longrightarrow \quad { C }_{ 6 } }{ H }_{ 12 }{ O }_{ 6 }+{ 6H }_{ 2 }{ O+{ 6O }_{ 2 } }$

Photosynthesis is a biochemical process. It is an anabolic, redox, and endothermic reaction.
Three raw materials are required by plants for the process of photosynthesis.

Carbon Dioxide- It is obtained by plants from the earth's atmosphere.
Water- It is absorbed by plants from the soil.
Sunlight- Without sunlight photosynthesis would not be possible. It is the primary source of energy on earth.

Additional Information:

Photosynthesis was observed for the first time in cyanobacteria.
The energy received from sunlight is converted into the chemical energy of food.
It is an oxidation-reduction reaction where oxidation of water occurs to O2 and the reduction of carbon dioxide occurs to sugars.
Several theories about how plants do photosynthesis have been given by many scientists:

- Aristotle and Theophrastus: Proposed that food was absorbed by plants from the soil.

- Stephan Hale: Proposed that plants obtain food from leaves.

- Ingen-Housz: Proved that plants purify the air in the presence of sunlight.

- De-Saussure- Proved that water is significant for photosynthesis.

- Blackman: Gave the law of limiting factors.

- Engelmann: Plotted the action spectrum for photosynthesis.

Ruben, Kamen, and Hashid demonstrated that oxygen in photosynthesis comes from water.

So, the correct answer is,” the equation that represents photosynthesis is
Carbon dioxide + water $\longrightarrow$ glucose + oxygen.”

Note: It should be remembered that in some organisms like bacteria photosynthesis is non-oxygenic and here only cyclic photophosphorylation takes place and only one photosystem is present. The reaction center contains the pigment B890 and it uses the UV radiation. No oxygen is evolved in bacterial photosynthesis as the proton and electron donor is hydrogen sulfide.