Question

The first step in photosynthesis is
A. Joining of 3-carbon atom to form glucose
B. Formation of ATP
C. Ionization of water
D. Excitement of an electron of chlorophyll by photon of light

Answer 1

Photosynthesis can be divided into two stages- the light dependent reaction and the light independent reaction. Special pigments in plant cell chloroplasts absorb the energy from certain light wavelengths, creating a molecular chain reaction called light-dependent reactions of photosynthesis.

Complete answer:
Plants are able to make their own food by using the energy from the sun. This process is known as photosynthesis. During this process, carbon dioxide from the atmosphere is taken in by leaves through stomata and used for making carbohydrates, mainly glucose and starch.

Photosynthesis consists of both light dependent and light-independent reactions. Light reaction occurs in plants inside the chloroplast thylakoids, where the pigments of chlorophyll are found. As light energy enters the pigment molecules, it energises the electrons inside them, and the thylakoid membrane shunts these electrons to an electron transport chain. Each step in the electron transport chain takes each electron to a lower energy state and uses its energy by ATP and NADPH production. Meanwhile, each chlorophyll molecule substitutes the missing electron with an electron of water; this method effectively separates water molecules to create oxygen.

After the light reactions occur, the light-independent or "dark" reactions occur in the stroma region of the chloroplast. In this process, also referred to as carbon fixation, the energy produced by the light reactions from the ATP and NADPH molecules drives a chemical pathway using carbon dioxide to produce a three-carbon sugar known as glyceraldehyde-3-phosphate (G3P). This sugar is then used by cells to create a broad range of other sugars and organic molecules. These reaction products are then transferred to other regions of the cell where they are broken down to produce more energy carrier molecules to fulfill the cell's metabolic demands.

Thus, the correct answer is option D i.eExcitement of an electron of chlorophyll by photon of light.

Note: Photosynthesis is essential for all living beings. Plants are the main producers of energy in the ecosystem. All other organisms depend on plants directly or indirectly for their food.