# DBT JRF 2022 — Question 108

Exam: DBT JRF 2022 · Section: B · Topic: Biochemistry › Thermodynamics of Living Systems · Difficulty: Medium

## Question

The entropy of a growing cell does NOT keep increasing continuously because:

## Options

- **A.** The cell is a highly structured system
- **B.** The information content in the DNA is very high
- **C.** Various regulatory loops provide feedback to the system
- **D.** The cell is an open system allowing both matter and energy to be exchanged with surroundings

## Answer

Option D

## Explanation

Thermodynamics of living cells: open systems: Living cells as thermodynamic systems: • They are OPEN SYSTEMS: exchange both matter (nutrients, metabolites, waste products) AND energy (heat, work) with the environment. • Closed systems: exchange only energy, not matter. • Isolated systems: exchange neither matter nor energy. Second Law of Thermodynamics and life: • Living cells maintain their highly ordered, low-entropy internal state by CONTINUOUSLY INCREASING ENTROPY of their surroundings. • $\Delta S_{\text{total}} = \Delta S_{\text{system}} + \Delta S_{\text{surroundings}} \geq 0$ • Cells export disorder (heat, CO₂, waste) to the environment, thus maintaining their own low entropy. This is why life requires a constant input of energy (food, sunlight) — to power the entropy export. Answer: Living cells are open thermodynamic systems exchanging both matter and energy with surroundings; they maintain low internal entropy by increasing environmental entropy.

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