GK: Class 12 General Q&A · Page 16
3,658 free answers on GK (General) for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
What are tissues made of?
Tissues are made of cells and extracellular matrix. The cells provide the functional component, while the extracellular matrix—composed of proteins, water, and other molecules—provides structural support and facilitates cellular communication. The cellular component varies by tissue type. Epithelial tissue consists primarily of tightly packed cells with minimal extracellular matrix, creating effective barriers. Connective tissue, conversely, contains relatively fewer cells
- GeneralClass 12All
What is cell and tissue?
A cell is the smallest structural and functional unit of life, while tissue is a group of similar cells working together toward a common function. The relationship between cells and tissues represents a fundamental organizational principle in biology. Cells are microscopic building blocks that contain all the machinery necessary for life, including genetic material (DNA), energy-producing structures (mitochondria), and protective membranes. Each cell can perform essential functions li
- GeneralClass 12All
What is a definition of tissue?
Tissue is defined as an organized collection of structurally similar cells and their intercellular substance that work together to perform one or more specific physiological functions. This biological definition emphasizes three key components: cellular similarity, organization, and functional specialization. The concept of tissue sits precisely between cells and organs in the biological hierarchy of organization. While individual cells are the basic units of life, tissue represents t
- GeneralClass 12All
What are the 4 types of tissue?
The human body contains four primary tissue types: epithelial tissue, connective tissue, muscle tissue, and nervous tissue. Each serves distinct, vital functions that sustain life. Epithelial tissue forms protective coverings and linings throughout the body, including your skin's outer layer and the interior surfaces of organs and blood vessels. This tissue acts as a barrier against pathogens and injury while also facilitating absorption and secretion. Connective tissue, the body's mo
- GeneralClass 12All
What disease causes tissue damage?
Tissue is a group of similar cells working together to perform a specific function in the body. Think of it as the next level of organization after individual cells—when cells with similar structures and purposes unite, they form tissue. This fundamental biological concept applies to all multicellular organisms, from plants to animals. In practical terms, tissue represents nature's way of organizing cellular labor. Just as workers in a factory specialize in different tasks, cell
- GeneralClass 12All
What are genes?
Genes are specific segments of DNA that contain the instructions for building proteins, which perform virtually all the functions in living organisms. Think of genes as individual recipes in the complete cookbook of life that is your genome. Each gene consists of a particular sequence of DNA bases (the chemical letters A, T, G, and C) that spells out instructions for making a specific protein or set of related proteins. Humans have approximately 20,000-25,000 genes distributed across 23 pairs
- GeneralClass 12All
Can DNA be damaged?
Yes, DNA can be damaged by numerous internal and external factors, and such damage occurs continuously in every cell of your body—an estimated 10,000 to 1,000,000 molecular lesions per cell per day. External sources of DNA damage include ultraviolet (UV) radiation from sunlight, which causes adjacent thymine bases to bond together forming thymine dimers, ionizing radiation (X-rays, gamma rays) that breaks DNA strands, environmental chemicals and pollutants (tobacco smoke, industrial che
- GeneralClass 12All
What is DNA made of?
DNA (deoxyribonucleic acid) is made of three fundamental chemical components organized into repeating units called nucleotides. Each nucleotide consists of a sugar molecule (deoxyribose), a phosphate group, and one of four nitrogenous bases: adenine (A), thymine (T), guanine (G), or cytosine (C). These nucleotides link together to form long chains, with the sugar of one nucleotide connecting to the phosphate group of the next, creating a sugar-phosphate backbone. Two of these chains wind arou
- GeneralClass 12All
Who discovered cells?
Robert Hooke, an English scientist, was the first person to observe and describe cells in 1665, making him the discoverer of cells as distinct structural units. Using a primitive compound microscope he had improved himself, Hooke examined thin slices of cork (dead plant tissue from tree bark) and observed tiny, box-like compartments that reminded him of the small rooms (cells) where monks lived in monasteries. He published his observations in his groundbreaking work "Micrographia," where he c
- GeneralClass 12All
What is mitosis and meiosis?
Mitosis and meiosis are two distinct types of cell division that serve different biological purposes in eukaryotic organisms. Mitosis is the process by which a single cell divides to produce two genetically identical daughter cells, each containing the same number and type of chromosomes as the parent cell. This form of division is essential for growth, tissue repair, and asexual reproduction. When you heal a cut, grow taller, or replace old skin cells, mitosis is responsible for generating t
- GeneralClass 12All
What is meiosis?
Meiosis is a specialized type of cell division that produces reproductive cells (gametes)—sperm in males and eggs in females—containing half the genetic material of normal body cells. This reduction division is essential for sexual reproduction because it ensures that when a sperm fertilizes an egg, the resulting offspring has the correct number of chromosomes rather than double the amount. In humans, for example, body cells contain 46 chromosomes (23 pairs), but through meiosis,
- GeneralClass 12All
How are cells formed?
Cells are formed exclusively through the division of pre-existing cells, a fundamental principle established by cell theory that states "all cells arise from pre-existing cells." This process, called cell division, involves a parent cell splitting into two or more daughter cells after replicating its genetic material and cellular components. In prokaryotic organisms like bacteria, cells divide through a relatively simple process called binary fission, where the circular DNA molecule replicate
- GeneralClass 12All
What is cell theory?
Cell theory is one of the fundamental principles of biology, establishing that all living organisms are composed of one or more cells, that the cell is the basic unit of life, and that all cells arise from pre-existing cells through division. This theory emerged gradually during the 17th-19th centuries through the work of multiple scientists and represents a cornerstone of modern biology, comparable in importance to atomic theory in chemistry or the theory of evolution in biology. Cell theory
- GeneralClass 12All
What is the largest cell in the human body?
The largest cell in the human body is the female egg cell, also called an ovum or oocyte, which measures approximately 100-120 micrometers (0.1-0.12 millimeters) in diameter. This is remarkably large by cellular standards—about the size of a period at the end of a sentence and actually visible to the naked eye under good lighting conditions. The egg cell's extraordinary size is functionally significant because it must contain enough cytoplasm, nutrients, and cellular machinery to suppor
- GeneralClass 12All
What are the 7 main functions of a cell?
The seven main functions of a cell encompass all the essential processes that define life at its most fundamental level. First, nutrition and metabolism involve taking in nutrients from the environment and converting them into usable energy and building materials through complex biochemical pathways. Cells break down glucose and other molecules through cellular respiration to produce ATP (adenosine triphosphate), the universal energy currency that powers all cellular work. Th
- GeneralClass 12All
What is cell structure?
Cell structure refers to the organized arrangement of components within a cell that enable it to perform essential life functions. At the most basic level, all cells share a common structural framework: a cell membrane (plasma membrane) that forms a selective barrier between the cell's interior and external environment, cytoplasm (the gel-like substance filling the cell), and genetic material (DNA) that stores hereditary information. This fundamental organization allows cells to maintain thei
- GeneralClass 12All
What are the two main types of cells?
The two main types of cells are prokaryotic and eukaryotic cells, which differ fundamentally in their internal organization and complexity. Prokaryotic cells are evolutionarily ancient, simple cells that lack a membrane-bound nucleus and other membrane-enclosed organelles. These cells, which include all bacteria and archaea, have their genetic material concentrated in a region called the nucleoid that isn't separated from the rest of the cell by a membrane. Prokaryotic cells are typically sma
- GeneralClass 12All
What is called a cell?
The term "cell" was coined by English scientist Robert Hooke in 1665 when he examined thin slices of cork under an early microscope and observed small, box-like compartments that reminded him of the small rooms (cells) that monks lived in at monasteries. While Hooke was actually observing the dead cell walls of plant tissue rather than living cells, his terminology stuck and became the universal name for these fundamental biological units. This historical naming reflects the compartmentalized
- GeneralClass 12All
What is a cell in a battery?
A cell in a battery is an electrochemical device that converts stored chemical energy into electrical energy through controlled chemical reactions between different materials. Each battery cell consists of three essential components: two electrodes (an anode and a cathode) made from different materials, and an electrolyte that allows ions to move between the electrodes while preventing direct electrical contact. When a circuit is connected, chemical reactions occur at both electrodes simultan
- GeneralClass 12All
What is a cell and its types?
A cell is the fundamental unit of life that exists in two primary forms: prokaryotic and eukaryotic cells, each with distinct characteristics and organizational complexity. Prokaryotic cells are simpler, lacking a membrane-bound nucleus, and include bacteria and archaea. These ancient cell types have their genetic material floating freely in the cytoplasm within a region called the nucleoid. Despite their simplicity, prokaryotic cells are remarkably successful, inhabiting virtually every envi