Download Introduction to cell biology: Milestones in cell biology, Cell theory, Properties of cell, and more Study notes Cell Biology in PDF only on Docsity!
• Classification of cell
Based on their structural features and complexity, cells can be divided into two main categories: prokaryotic cells and eukaryotic cells. Prokaryotic cells are less complex and lack a nucleus and membrane-bound organelles, while eukaryotic cells are more complex and have a nucleus and various membrane-bound organelles. Prokaryotic cells are found in bacteria and archaea, while eukaryotic cells are found in protists, fungi, plants, and animals. Eukaryotic cells can be further classified into two categories based on the presence or absence of cell walls. Plant cells have a cellulose cell wall, chloroplasts responsible for photosynthesis, and a large central vacuole that helps regulate the cell's water balance. Animal cells lack a cell wall and chloroplasts, but have various membrane-bound organelles such as mitochondria, lysosomes, and peroxisomes that carry out specific functions. Furthermore, cells can also be classified based on their functions and characteristics, such as stem cells, muscle cells, nerve cells, and blood cells. These classifications are based on the unique features and specialized functions of these cells within the body.
• Structural organization of prokaryotic and eukaryotic cell
The structural organization of prokaryotic and eukaryotic cells is distinct from each other. Prokaryotic cells are relatively small and less complex. They do not have a nucleus or other membrane-bound organelles, and their genetic material is found in a region called the nucleoid, which is not enclosed by a membrane. The cell membrane encloses the cytoplasm, which contains ribosomes, enzymes, and other molecules required for metabolic activities. Prokaryotic cells also possess a cell wall outside the cell membrane that offers additional support and protection. Pili and flagella are other external structures that some prokaryotic cells have, which serve various functions such as attachment, movement, and communication. In contrast, eukaryotic cells are typically larger and more complex in structure. They have a
nucleus that is enclosed by a nuclear membrane, and their genetic material is organized into chromosomes. Eukaryotic cells also contain other membrane-bound organelles such as mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosomes, which perform specific functions such as energy production, protein synthesis, and waste disposal. Eukaryotic cells are also surrounded by a cell membrane that separates the internal and external environment of the cell. Plant cells have an additional cell wall made of cellulose outside the cell membrane, which provides rigidity and support to the cell. Eukaryotic cells also have a cytoskeleton made of protein fibers that provide structure and shape to the cell and help with movement. The structural organization of prokaryotic and eukaryotic cells reflects their differences in complexity and function. Prokaryotic cells have a simpler structure but are capable of performing all the necessary metabolic processes. On the other hand, eukaryotic cells have a more complex structure with specialized organelles that perform specific functions.
• Comparison of microbial, plant and animal cells
Microbial cells, plant cells, and animal cells are three distinct types of cells that differ in their structures and functions. Microbial cells, including bacteria, archaea, and some protists, are single-celled organisms that lack membrane-bound organelles such as a nucleus or mitochondria. Their genetic material is located in the nucleoid region, and metabolic processes occur in the cytoplasm. Some microbial cells have a cell wall outside the cell membrane for additional protection and support. Plant cells, on the other hand, have a unique cell wall made of cellulose outside the cell membrane, providing rigidity and support, and chloroplasts responsible for photosynthesis. They also have a large central vacuole, which helps regulate the cell's water balance, and a cytoskeleton made of protein fibers that provides structure and shape to the cell and helps with movement. Animal cells lack a cell wall and chloroplasts but have various types of membrane-bound organelles such as mitochondria, lysosomes, and peroxisomes that carry out specific functions within the cell. The cell membrane encloses animal cells, separating the internal and external environments, and they also have a cytoskeleton made of protein fibers that provides structure
The evolution of cells has brought about the vast diversity of life we observe today. Comprehending the origin and evolution of cells is necessary for understanding the history of life on Earth and the relationships between different organisms.
• Theory of microscopy and types of microscopes
The field of microscopy theory deals with the principles and concepts that govern the function of microscopes, which are instruments used to magnify and visualize objects that are too small to be seen with the naked eye. This field encompasses the study of the physical principles that dictate the interaction of light and matter, and how these principles are applied in the design and operation of microscopes. Microscopes come in several types, each with its own set of advantages and limitations. The most commonly used type is the optical microscope, which employs visible light to magnify objects and can be either simple or compound in design. Simple microscopes contain a single lens, while compound microscopes use two or more lenses. Optical microscopes can magnify objects up to 2000 times their actual size. Electron microscopes, on the other hand, utilize a beam of electrons to magnify objects and can achieve much higher magnifications than optical microscopes, up to 10 million times their actual size. There are two types of electron microscopes: transmission electron microscopes (TEM) and scanning electron microscopes (SEM). TEMs transmit electrons through the sample to produce an image, while SEMs scan the surface of the sample with a beam of electrons to produce an image. Scanning probe microscopes are another type of microscope that use a probe to scan the surface of a sample and generate a three-dimensional image. They are capable of extremely high resolution and can even image individual atoms. Finally, X-ray microscopes employ X-rays to illuminate and magnify objects, producing images with very high resolution that can be used to study the structure of materials at the atomic level.
The choice of microscope depends on the specific application and the nature of the sample being studied, as each type of microscope has its own unique strengths and weaknesses.
