GK: Class 12 General Q&A · Page 183
3,658 free answers on GK (General) for Class 12 students, across CBSE, ICSE and State boards.
Question & Answer
Questions
- GeneralClass 12All
Give full form of ATP.
ATP stands for Adenosine Triphosphate. This molecule serves as the primary energy currency of all living cells, storing and transferring energy needed for virtually every cellular process including muscle contraction, nerve impulse transmission, chemical synthesis, and active transport across membranes. Structurally, ATP consists of adenosine (a nitrogenous base adenine attached to a ribose sugar) bonded to three phosphate groups. The high-energy bonds between the phosphate groups, pa
- GeneralClass 12All
Give two examples of cells where 'cell shape' changes frequently.
Amoeba is a classic example of a cell that constantly changes its shape through a process called amoeboid movement. This unicellular organism extends temporary projections of its cytoplasm called pseudopodia (false feet) in different directions to move, engulf food through phagocytosis, and respond to environmental stimuli. The shape changes are facilitated by the dynamic rearrangement of its cytoskeleton, particularly actin filaments, which allow the cell membrane to bulge outward and flow i
- GeneralClass 12All
Give two points of importance of osmosis.
Osmosis plays a vital role in maintaining cell turgidity and shape, which is especially critical in plant cells where the influx of water creates turgor pressure against the rigid cell wall, keeping plants upright, firm, and structurally sound. Without adequate turgor pressure maintained through osmosis, plants wilt and droop because their cells become flaccid. This same principle allows plant cells to perform growth movements and maintain the rigidity needed for leaves to capture sunlight ef
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Phospholipids are an important component of which part of the cell. Name it.
Phospholipids are the fundamental structural components of the plasma membrane (also called cell membrane), forming a phospholipid bilayer that defines the cell's boundary and controls what enters and exits the cell. Each phospholipid molecule has a hydrophilic (water-loving) phosphate head and two hydrophobic (water-fearing) fatty acid tails, and they spontaneously arrange themselves in two layers with the hydrophobic tails facing inward and the hydrophilic heads facing the aqueous environme
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If you are provided with some vegetables to cook, you generally add salt into the vegetables during cooking process. After adding salt, vegetables release water. What mechanism is responsible for this?
The mechanism responsible for water release from vegetables when salt is added is exosmosis, a specific type of osmosis where water moves out of cells into the surrounding environment. When salt is sprinkled on vegetables, it creates a hypertonic solution on the vegetable surface—the salt concentration outside the cells is much higher than the concentration of dissolved substances inside the vegetable cells. Following osmotic principles, water moves from the area of lower solute concent
- GeneralClass 12All
We eat food composed of all the nutrients like carbohydrates, proteins, fats, vitamins, minerals and water. After digestion, these are absorbed in the form of glucose, amino acids, fatty acids, glycerol etc. What mechanisms are involved in absorption of digested food and water?
The absorption of digested nutrients involves multiple specialized mechanisms working simultaneously in the small intestine, primarily through the villi and microvilli that vastly increase the surface area for absorption. Simple diffusion allows small, lipid-soluble molecules like fatty acids and glycerol to pass directly through the cell membrane down their concentration gradient without energy expenditure. Facilitated diffusion uses specific carrier proteins or channel proteins to transport
- GeneralClass 12All
A person takes concentrated solution of salt, after sometime, he starts vomiting. What is the phenomenon responsible for such situation? Explain.
The phenomenon responsible for vomiting after consuming a concentrated salt solution is exosmosis, where water moves out of cells due to osmotic imbalance. When highly concentrated salt enters the digestive system, it creates a hypertonic environment in the stomach and intestines—meaning the salt concentration outside the cells is much higher than inside them. According to osmotic principles, water moves from the region of lower solute concentration (inside the cells of the stomach lini
- GeneralClass 12All
Why is endocytosis found in animals only?
Endocytosis is predominantly found in animal cells because plant cells, fungi, and bacteria possess rigid cell walls that physically prevent the plasma membrane from invaginating and forming vesicles required for this process. Animal cells have only a flexible plasma membrane without an external cell wall, allowing the membrane to fold inward, engulf materials from outside the cell, and pinch off to form intracellular vesicles. This structural flexibility is essential for the three main types
- GeneralClass 12All
Why does the skin of your finger shrink when you wash clothes for a long time?
The wrinkling or shrinking of finger skin during prolonged water exposure is primarily caused by osmosis, a process where water moves from an area of lower solute concentration to higher solute concentration across a semi-permeable membrane. When you wash clothes for an extended period, your skin cells are exposed to hypotonic water (water with fewer dissolved substances than your cells). Water enters the skin cells through osmosis, causing them to swell initially. However, the outermost laye
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Why Vegetable Vendors Sprinkle Water
Vegetable vendors regularly sprinkle water on their produce to maintain freshness and visual appeal by exploiting the principles of osmosis and turgor pressure in plant cells. When vegetables are harvested, they are severed from their water source and begin losing moisture through transpiration and evaporation, causing their cells to lose turgor pressure—the internal hydrostatic pressure that keeps plant cells firm and rigid. As water leaves the cells, they become flaccid and the vegeta
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Father of Microscopy
Antonie van Leeuwenhoek (1632-1723), a Dutch scientist and tradesman, is widely recognized as the "Father of Microscopy" for his pioneering work in developing high-quality single-lens microscopes and his extraordinary observations of the microscopic world.
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Temperature Effects on Osmosis
Temperature significantly affects the rate of osmosis, though it does not change the fundamental direction of water movement dictated by concentration gradients. As temperature increases, the kinetic energy of water molecules rises, causing them to move faster and collide more frequently with the selectively permeable membrane. This increased molecular motion directly translates to a higher rate of osmotic water movement across the membrane at 37°C (body temperature), osmosis occurs noticeabl
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Conditions Required for Osmosis
Osmosis requires three essential conditions to occur: a selectively permeable membrane (also called a semi-permeable membrane), a concentration difference of solute across that membrane, and the presence of a solvent, typically water. The selectively permeable membrane is crucial because it must allow water molecules to pass freely while restricting or preventing the movement of dissolved solutes, creating the selective permeability that drives the process. Without a concentration gradient&md
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Consequences of Plasma Membrane Rupture
If the plasma membrane ruptures or breaks down, the cell will lose its structural integrity and undergo rapid death through a process resembling necrosis. The membrane serves as the critical boundary that maintains the cell's internal environment, keeping essential components like proteins, nucleic acids, organelles, and ions contained while excluding harmful substances. Once this barrier is breached, the cytoplasm leaks out into the surrounding environment, and the carefully regulated concen
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De-shelled Egg in Concentrated Salt
When a de-shelled egg (with its protective shell removed chemically, leaving only the semi-permeable membrane) is placed in a concentrated salt solution, it will undergo osmotic shrinkage and visibly decrease in size within 5 minutes. The egg membrane acts as a selectively permeable barrier, allowing water molecules to pass through while largely restricting dissolved salts. Because the salt concentration outside the egg is much higher than inside, water moves outward from the egg's interior t
- GeneralClass 12All
Exceptions to Classical Cell Theory
. While the cell theory remains fundamentally sound, several biological entities and structures present notable exceptions that have refined our understanding since the original postulates. Viruses represent the most significant exception—they are acellular entities that cannot carry out metabolic processes independently and require host cells to replicate, yet they contain genetic material and evolve. This has led scientists to debate whether viruses should be considered "livin
- GeneralClass 12All
Types of Transport Across Cell Membranes
Cell membranes regulate molecular traffic through several distinct transport mechanisms, broadly categorized as passive and active transport. Passive transport includes simple diffusion (movement of small, nonpolar molecules like oxygen and carbon dioxide directly through the lipid bilayer), facilitated diffusion (movement of polar molecules and ions through protein channels or carriers, following their concentration gradient), and osmosis (the specific diffusion of water across a selectively
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Multi-Nucleated Cell Examples
Multi-nucleated cells, or syncytial cells, contain multiple nuclei within a single continuous cytoplasm and represent specialized adaptations for specific functions. Skeletal muscle fibers are perhaps the most prominent example in human physiology these elongated cells form when multiple precursor cells (myoblasts) fuse during development, creating fibers that can contain hundreds of nuclei distributed along their length. This multi-nucleated arrangement supports the high metabolic demands an