Cell Structure and Functions PDF

Cell: Structure And Functions This chapter will explore the fascinating world of cells, the fundamental building blocks of life. We will delve into the structure and functions of these microscopic units, uncovering the secrets that make life possible.  Introduction to the Cell 1...

Cell: Structure And Functions This chapter will explore the fascinating world of cells, the fundamental building blocks of life. We will delve into the structure and functions of these microscopic units, uncovering the secrets that make life possible.  Introduction to the Cell 1 The Basic Unit of Life The cell is the smallest structural unit of a living organism, often referred to as "the basic unit of life". 2 Size and Shape Cells vary in size and shape, from microscopic bacteria to large nerve cells. The size of a cell is determined by its function. 3 Types of Cells There are two main types of cells: prokaryotic and eukaryotic. Prokaryotic cells are simpler and lack a nucleus, while eukaryotic cells have a well-defined nucleus. 4 Cytology Cytology is the branch of science that studies cells, their components, and their functions. Story of the Microscope 1 Zacharias Janssen (1585) Zacharias Janssen is credited with creating the first compound microscope, although the exact details of its discovery remain unclear. 2 Anton van Leeuwenhoek Leeuwenhoek used a simple microscope with a single lens to observe bacteria, becoming the first person to see these microscopic organisms. 3 Robert Hooke (1665) Hooke observed a piece of cork under a compound microscope and noticed small compartments, which he named "cells" due to their resemblance to small rooms. He discovered the cells.  Types of Microscopes Simple Microscope Compound Microscope Electron Microscope Consists of a single convex Uses two convex lenses with Employs electron beams to lens with a short focal short focal lengths, illuminate a specimen, offering length, providing achieving magnifications of magnifications up to 200,000 magnification up to 15X. 1000X or more. times greater than a compound microscope.  Discovery of the Cell Robert Hooke In 1665, Hooke observed cork cells under a microscope, but his limited magnification prevented him from seeing internal details. Anton van Leeuwenhoek Leeuwenhoek's higher-powered microscope revealed movement in cells, leading him to conclude that these microscopic entities were alive. Robert Brown In 1833, Brown described the nucleus present in orchid cells, providing early insights into cell structure.  Cell Theory Founders: The cell theory was developed by Matthias Schleiden and Theodor Schwann in the mid-19th century, with contributions from Rudolf Virchow. Three Postulates of Cell Theory 1. All Living Organisms are Composed of Cells 2. Cells are the Fundamental Building Blocks of Life 3. New Cells are Formed from Pre-existing Cells Types of Organisms: based on number of cells Unicellular Organisms These organisms consist of a single cell that performs all life functions. Examples include Amoeba, Paramoecium, and bacteria. Bacteria Types of Organisms: based on number of cells Multicellular Organisms These organisms are composed of numerous cells that work together to perform specialized functions and form tissues, organs, and organ systems. Examples include fungi, plants, and animals.  Types of Organisms: based on structure and functions Prokaryotic Cells Eukaryotic Cells 1. Generally small (0.1 − 5 µ𝑚), 1. Generally larger (5 − 100 µ𝑚), 2. no well-defined nucleus, 2. possess a well-defined nucleus, 3. have a single circular chromosome, and 3. have multiple linear chromosomes, and 4. no membrane-bound organelles. 4. contain membrane-bound organelles. Examples: bacteria. Example: human cells. Shape and Size of cell Cells differ greatly in size, shape and activities Mycoplasmas, the smallest cells, are only 0.3 µm in length. Bacteria could be 3 to 5 µm. The largest isolated single cell is the egg of an ostrich. Among multicellular organisms, human red blood cells are about 7.0 µm in diameter. Nerve cells are some of the longest cells. Shape and Size of cell Cells differ greatly in size, shape and activities Mycoplasmas, the smallest cells, are only 0.3 µm in length. Bacteria could be 3 to 5 µm. The largest isolated single cell is the egg of an ostrich. Among multicellular organisms, human red blood cells are about 7.0 µm in diameter. Nerve cells are some of the longest cells. Components and Organelles of the Cell The cell membrane, cytoplasm, and nucleus are the three main parts of a cell Plasma Membrane Cell Wall Cytoplasm Nucleus The outermost covering of A rigid structure present in The jelly-like substance The control center of the the cell, regulating the entry plant cells, providing inside the cell membrane, cell, containing genetic and exit of substances. It is shape, support, and containing various information and regulating composed of lipids and protection. It is composed organelles and cell cellular activities. It is proteins. of cellulose, hemicellulose, inclusions. enclosed by a double and pectin. membrane.