Test: The Cell - SSC CGL MCQ

In 1665, Robert Hooke observed small chamber-like structures in cork, which he termed as "cells." This discovery marked the beginning of the cell theory, which states that cells are the fundamental units of life in all living organisms. Cells can exist in various forms and carry out specific functions necessary for the survival of the organism.

The structures that are present in all types of cells, whether prokaryotic or eukaryotic, include:

• Plasma membrane: This acts as a protective barrier, controlling what enters and leaves the cell.
• Cytoplasm: This is the gel-like substance within the cell, where various cellular processes occur.
• Ribosomes: These are the sites of protein synthesis, essential for cell function.

Other structures, like the nucleus, mitochondria, and chloroplasts, are specific to eukaryotic cells and are not found in prokaryotic cells.

The combined content of the cytoplasm and nucleoplasm inside a cell is referred to as protoplasm. Protoplasm is considered the physical basis of life as it contains all the necessary components for cellular processes and functions. It encompasses the living structures within the cell that are essential for its survival and activities.

The main principles of cell theory, state that all living organisms are composed of cells and their products. This principle underscores the fundamental idea that cells are the building blocks of life, forming the basis of all living organisms. This concept revolutionized our understanding of biology and laid the foundation for modern biological sciences.

The Nobel Prize in Physiology or Medicine in 2016 was awarded to Japanese cell biologist Yoshinori Ohsumi for his groundbreaking work on autophagy. Autophagy is a vital cellular process where cells degrade and recycle their own components using lysosomes. Ohsumi's research significantly advanced our understanding of how cells maintain their health and respond to changing environmental conditions.

Plant cells differ from animal cells in various ways, one significant difference being the presence of chloroplasts in plant cells. Chloroplasts are responsible for photosynthesis, the process by which plants convert sunlight into energy. This unique feature allows plants to produce their food and gives them their characteristic green color.

The primary difference between prokaryotic and eukaryotic cells lies in the presence of membrane-bound organelles. Prokaryotic cells lack membrane-bound organelles like a nucleus, while eukaryotic cells have membrane-bound organelles, including a nucleus that houses the genetic material. This distinction is fundamental in understanding the complexity and organization of different cell types.

Chromosomes are composed of DNA and special proteins called histones. Histones play a crucial role in facilitating the condensed form of DNA within chromosomes. This compact structure ensures efficient packaging of genetic material during cell division, allowing for accurate distribution of DNA to daughter cells.

The point where chromatids are held together on a chromosome during cell division is called the centromere. This region plays a vital role in ensuring the proper alignment and separation of chromatids during cell division, contributing to the accurate distribution of genetic material to daughter cells.

The cell cycle serves the crucial function of facilitating cell growth and division into daughter cells. This process is essential for the reproduction and maintenance of multicellular organisms.

The S phase, also known as the Synthesis phase, is the stage of the cell cycle where DNA replication occurs. This crucial step ensures that each daughter cell receives an identical copy of the genetic material.

The G0 stage is a quiescent phase in which cells are not actively dividing. Cells in this stage are in a resting state and do not proceed with the typical cell cycle activities like division or DNA replication.

Non-living inclusions within a cell are collectively referred to as deutoplasm. These structures are distinct from the living components of the cell and may include various substances such as stored nutrients, pigment granules, or other materials that serve specific functions within the cell. Deutoplasm contributes to the overall composition and functionality of the cell, supporting its metabolic processes and activities.

The phrase "Omnis cellula e cellula" is Latin for "every cell originates from another cell." This statement is a fundamental tenet of cell theory, emphasizing that all cells arise from pre-existing cells through cell division. It rejects the notion of spontaneous generation and highlights the continuous process of cell reproduction that underpins the growth, development, and maintenance of living organisms.

A karyotype is a term used to describe the number and appearance of chromosomes in the nucleus of a eukaryotic cell, or it can refer to the complete set of chromosomes. It provides a visual representation of an individual's chromosomes, highlighting their size, shape, and number. Karyotyping is a valuable tool in genetics and cytogenetics, aiding in the identification of chromosomal abnormalities and genetic disorders.