Question

Cell theory was formulated by ____________.

• A. Antonie Von Leeuwenhoek
• B. Schleiden and Schwann
• C. Robert Brown
• D. Singer and Nicolson

Hint:

While Schleiden and Schwann formulated the baseline Cell Theory, it had a major limitation: it could not explain *how* new cells are created. This missing link was resolved in 1855 by Rudolf Virchow, who introduced the phrase: \[ \text{\textit{Omnis cellula-e cellula}} \quad \Longrightarrow \quad \text{New cells arise only from pre-existing cells} \] Together, these contributions define the modern cell theory.

Answer 1

The Correct Option is B

Concept: The development of cell biology as a unified branch of science began with establishing systematic principles describing the fundamental building blocks of all living organisms. These principles are summarized collectively as the

Cell Theory.

Step 1: Historical context of the Cell Theory formulation
In the late 1830s, two German scientists working independently arrived at complementary conclusions regarding living organisms:

• Matthias Schleiden (1838): A German botanist who examined a wide variety of plant tissues and concluded that all plants are entirely composed of different kinds of cells, which form the tissues of the plant.

• Theodor Schwann (1839): A German zoologist who studied different types of animal cells. He reported that animal cells have a thin outer layer (now known as the plasma membrane) and noted that the presence of a cell wall is a unique feature characteristic only of plant cells. Based on this, he proposed the hypothesis that the bodies of both animals and plants are composed of cells and products of cells.
These two scientists combined their observations to formally outline and propose the classic Cell Theory.

Step 2: Analysis and elimination of other options
Let us look at the contributions of the other scientists listed in the options:

• Option (1) Antonie Von Leeuwenhoek: He was the first to observe, describe, and record a live, free-living cell (such as bacteria, protozoans, and spermatozoa) using his modified high-magnification single-lens microscopes.

• Option (3) Robert Brown: He discovered and named the central dark spherical structural component of the cell—the nucleus—in orchid root cells in the year 1831.

• Option (4) Singer and Nicolson: They proposed the widely accepted Fluid Mosaic Model in 1972 to describe the structural arrangement and dynamic nature of the plasma membrane.
Thus, option (2) is the accurate answer.