Problem 134 - Objective Biology for NEET

Question

Plants obtain most of its carbon from (a) Atmosphere (b) Water (c) Soil (d) All of these

Step-by-Step Solution

Answer

The most correct answer is (a) Atmosphere. It's where plants obtain most of their carbon from because during photosynthesis they use carbon dioxide from the atmosphere.

Step 1: Understanding photosynthesis

Firstly understand that in photosynthesis, plants take in carbon dioxide, water, and sunlight to produce glucose and oxygen. The glucose is used as a food source and the oxygen is released into the atmosphere.

Step 2: Identifying the source of carbon

The next step is to remember that the source of carbon in this process comes from the carbon dioxide in the atmosphere.

Key Concepts

Photosynthesis

Photosynthesis is the process by which plants, algae, and some bacteria convert light energy, usually from the sun, into chemical energy stored in glucose. This process is essential for life on Earth as it forms the base of the food chain and provides oxygen for other living organisms. In simple terms, photosynthesis can be divided into two main stages: the light-dependent reactions and the light-independent reactions.

During the light-dependent reactions, sunlight is absorbed by chlorophyll in plant cells, and this energy is used to split water molecules into oxygen, protons, and electrons. The oxygen is released as a byproduct into the atmosphere. In the light-independent reactions, also known as the Calvin Cycle, carbon dioxide from the atmosphere is combined with the electrons and protons to produce glucose. This glucose serves as an energy source for the plant and can be converted into other forms like starch for storage.

To summarize, photosynthesis is crucial not only for plants to create their own food but also for providing oxygen to support life processes on Earth. It highlights the interconnectedness of plant life and the broader ecosystem.

Carbon Dioxide Source

The primary source of carbon for plants during photosynthesis comes from carbon dioxide present in the atmosphere. This carbon dioxide is essential for the synthesis of glucose, which is the energy source for the plant.

Atmospheric carbon dioxide enters the plant through tiny openings on the plant’s leaves called stomata. Once inside the leaf, the carbon dioxide moves into cells and reaches the chloroplasts, where photosynthesis occurs. Environmental factors, such as light intensity and the availability of water, can influence the rate at which carbon dioxide is absorbed by plants.

Some natural sources of carbon dioxide in the atmosphere include:

• Respiration by animals and plants
• Decay of organic material
• Combustion of fossil fuels

Plants play a significant role in regulating levels of atmospheric carbon dioxide, making them vital contributors to maintaining ecological balance.

Glucose Production

Glucose production is the primary aim of the photosynthesis process. During photosynthesis, plants convert carbon dioxide and water into glucose and oxygen, using the energy captured from sunlight. This glucose is a critical organic molecule that serves several important functions within the plant.

The general equation for photosynthesis is: \[6 CO_2 + 6 H_2O + ext{light energy} \rightarrow C_6H_{12}O_6 + 6 O_2\]

• Glucose provides the energy required for various plant functions, including growth, reproduction, and repair.
• It can be converted into other carbohydrates like starch and cellulose, the latter being a vital structural component of plant cell walls.
• Glucose can also be stored for future use during times when photosynthesis might not be as active, such as during the night or in winter.

Through glucose production, plants not only sustain themselves but also support other life forms by providing energy and matter through food chains.