Which gas is evolved during photosynthesis?

Appeared in: MNS 2015

Explanation

Photosynthesis is a biological process where plants convert light energy into chemical energy.
During this process, plants take in carbon dioxide (CO₂) from the air and water (H₂O) from the soil.
The key outcome is the production of glucose (C₆H₁₂O₆) for energy and the release (evolution) of oxygen (O₂) as a byproduct.
This release of oxygen is what makes plant life essential for sustaining aerobic life on Earth.

Option B: Nitrogen gas (N₂) makes up about 78% of the atmosphere, but plants cannot use it directly. It is not involved in the gas exchange of photosynthesis.
Option C: Carbon dioxide is a reactant, not a product. It is consumed by the plant during the Calvin cycle (light-independent reactions) to build carbohydrate molecules.
Option D: This option is incorrect because a correct answer, Oxygen, is listed among the choices.

Clinical Relevance

Nursing practice connection: Knowing The concept tested is the understanding of the process of photosynthesis, specifically identifying the gaseous byproduct helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Understanding the role of oxygen is fundamental to nursing. The oxygen produced by photosynthesis is the same oxygen that is essential for human cellular respiration.
In clinical practice, nurses constantly monitor a patient's oxygenation status (e.g., using pulse oximetry) because a lack of oxygen can quickly lead to tissue damage and organ failure.
The balance between oxygen and carbon dioxide is critical for maintaining the body's acid-base balance, a core physiological concept in patient care.

How to Approach the Question

First, identify the key terms in the question: 'gas evolved' and 'photosynthesis'.
'Evolved' means 'released' or 'given off'.
'Photosynthesis' is the process plants use to make food.
Recall the basic inputs and outputs of photosynthesis. Inputs are sunlight, water, and carbon dioxide. Outputs are glucose (sugar) and oxygen.
Based on this, the gas that is 'evolved' or released is oxygen.
Evaluate the options: Oxygen is a product, Carbon dioxide is a reactant, and Nitrogen is not directly involved. Therefore, Oxygen is the correct choice.

Concept Tested & Keywords

Concept Tested: The concept tested is the understanding of the process of photosynthesis, specifically identifying the gaseous byproduct.
Stem keywords: gas evolved, photosynthesis
Lead-in keywords: Which

QWdmIvYHX7Z3DTCv16hbVl

Practise the full MNS 2015

Attempt every question from this paper in a timed mock, then review the full solution for each one.