Cell: The Building Block of Life – Notes, MCQs, Quiz & Worksheet

An abnormal number of chromosomes typically results from errors during karyokinesis (nuclear division), specifically during the separation of chromosomes or chromatids, leading to unequal distribution into daughter cells.

ATP synthase is a key enzyme located in the inner mitochondrial membrane, responsible for the vast majority of ATP production during cellular respiration. Its inhibition would severely reduce the cell's energy supply.

Viruses lack cellular organelles and the machinery for independent metabolism and energy production, making them obligate intracellular parasites. They cannot carry out life processes without hijacking a host cell's cellular machinery.

A eukaryotic cell is characterized by the presence of a true nucleus and other membrane-bound organelles, distinguishing it from prokaryotic cells which lack these features.

The bursting of a red blood cell due to excessive water intake in a hypotonic solution is specifically known as hemolysis. Plasmolysis occurs in plant cells, and cremation refers to burning, while turgidity is firmness in plant cells.

If a plant cell's central vacuole loses all its water, the cell would lose its turgidity, causing the cell membrane to pull away from the cell wall (plasmolysis). This would lead to wilting of the plant and loss of structural support.

Ribosomes are found in both prokaryotic and eukaryotic cells, and their primary function in both types of cells is protein synthesis.

While plants have cell walls and chloroplasts, algae are a diverse group; some forms are unicellular, eukaryotic, possess chloroplasts for photosynthesis, but may lack a rigid cell wall, or have cell walls composed of different materials than plants.

The presence of ribosomes on its surface gives the RER its "rough" appearance and its role in protein synthesis, whereas the SER lacks ribosomes and is involved in lipid synthesis, detoxification, and calcium storage.

The cell membrane is described as a "fluid mosaic model" because its components (lipids and proteins) are not static but can move laterally within the membrane (fluidity), and these components are arranged in a dynamic, mosaic-like pattern rather than a rigid, fixed structure.

Active transport involves the movement of substances against their concentration gradient, requiring energy (ATP). Pumping ions against their gradient is a classic example.

The nucleus is called the "control center" because it houses the cell's genetic material (DNA) in chromosomes. It regulates all cellular activities by controlling gene expression, thereby directing protein synthesis and cell division.

In many freshwater unicellular organisms, the contractile vacuole actively pumps out excess water that enters the cell by osmosis, preventing lysis.

The cell theory is fundamental because it establishes that all living organisms are composed of cells, cells are the basic unit of life, and all cells arise from pre-existing cells. This provides a unifying principle for understanding the structure, function, and origin of all life forms.

The phospholipid bilayer, with its hydrophobic interior and hydrophilic exterior, acts as a barrier to most polar and large molecules, giving the membrane its selective permeability.

The abundance of ribosomes, RER, and Golgi apparatus indicates a cell highly active in synthesizing, modifying, and packaging proteins for secretion.

Mitochondria are the primary sites of cellular respiration, which is the process that generates the vast majority of the cell's ATP (adenosine triphosphate), the main energy currency.

The Golgi apparatus is directly responsible for the modification, sorting, and packaging of proteins and lipids into vesicles for secretion or delivery to other cellular destinations.

DNA polymerase is the enzyme responsible for synthesizing new DNA strands during DNA replication, so its mutation would directly impair this process.

Prokaryotic cells are defined by their lack of membrane-bound organelles and a true nucleus. They do have ribosomes and a cell wall.

These cells have many ribosomes and an extensive rough endoplasmic reticulum because digestive enzymes are proteins. Ribosomes are the sites of protein synthesis, and the RER is where these proteins are folded, modified, and prepared for transport and secretion.

Robert Hooke observed honeycomb-like compartments in cork and called them "cells" in 1665.

A large surface area to volume ratio allows small cells to efficiently exchange nutrients and waste products with their environment. As cell size increases, the volume grows faster than the surface area, making it harder for substances to diffuse in and out adequately to meet metabolic demands, thus limiting cell size.

One of the fundamental tenets of the cell theory is that all living organisms are composed of one or more cells. Not all cells contain a nucleus (prokaryotes), and cells do not spontaneously generate.

Plant vacuoles are typically larger because they play a crucial role in maintaining turgor pressure against the cell wall, storing water, nutrients, and waste products, and contributing to cell growth. Animal cells often have smaller, more numerous vacuoles primarily for temporary storage or transport.

The Smooth Endoplasmic Reticulum (SER) is primarily responsible for lipid and steroid hormone synthesis, as well as the detoxification of drugs and poisons.

Phagocytosis is a type of endocytosis where a cell engulfs large particles, bacteria, or other cells by extending its plasma membrane around them, forming a phagosome. It is crucial for immune cells like macrophages to defend against pathogens and for certain organisms to acquire nutrients.

Lysosomes contain hydrolytic enzymes that break down waste materials, cellular debris, and worn-out or unneeded proteins. A high rate of protein degradation would imply increased lysosomal activity.

The presence of a nucleoid region (where genetic material is located without a membrane) and the absence of membrane-bound organelles are defining characteristics of a bacterial (prokaryotic) cell.

As a cell grows, its volume increases much faster than its surface area. The surface area (cell membrane) is responsible for exchanging nutrients and waste. If the cell gets too large, the surface area won't be sufficient to meet the metabolic demands of the increased volume, making exchange inefficient and limiting cell size.