Introduction to Cells

Introduction to Cells

• Cells are covered in detail
• The channel provides videos for commerce subjects, accessible via the DAV School search on YouTube.
• All living organisms on Earth share similar basic structure and function.
• Living organisms are made of cells, like buildings are made of bricks.
• Organisms can be unicellular (single-celled) or multicellular (many-celled).
• All living organisms perform basic functions such as nutrition, respiration, growth, reproduction, and excretion, relying on cellular activities
• Every cell can perform functions of nutrition, respiration, and excretion.

Why Study Cells?

• Early scientists needed microscopes to observe cells due to their small size.
• Robert Hooke observed compartment-like structures in cork slices under a microscope, naming them "cells".
• Hooke derived the term "cell" from the Latin word "cellula," meaning small compartment.

Cell Structure & Variety

• All living organisms are composed of cells that vary in number, shape, and size.
• Cell shapes and sizes differ significantly across organisms.
• New cells replace old ones, a process typically imperceptible due to its small scale.
• Individual cells contain all vital fluids and structures necessary for the organism to live and function.

Cell Number

• Organisms are classified based on cell number as either unicellular or multicellular.
• Unicellular organisms consist of a single cell, while multicellular ones consist of many cells.
• Unicellular organisms are small and require a microscope to be seen, whereas multicellular organisms are larger due to their cell count.
• Multicellular organisms, like earthworms, are composed of numerous cells.
• Examples: Amoeba is unicellular; animals and birds are multicellular.

Cell Shape

• Cell shapes vary among different organisms and within different parts of the same organism.
• A cell's shape is determined by its location and function within the body.
• Nerve cells are long and fiber-like, which aids in signal transmission throughout the body.
• Nerve cells are responsible for transmitting signals, leading to sensations and actions.

Cell Size

• Cell sizes vary, with most requiring a microscope for observation due to their small size.
• Cell sizes typically range from 0.1 to 0.5 micrometers.
• Chicken eggs are single cells large enough to be seen unaided.
• Eggs consist of a yolk, albumen (white part), and a shell, encapsulating air space inside, forming a single, directly observable cell.
• Micrometer Conversion: 1 µm = 10⁻⁶ meters.

Observing Cells: Experiment with Cheek Cells

• Epithelial cells are collected by gently scraping a toothpick against the inner cheek.
• Material collected is placed on a glass slide, spread out, and stained with methylene blue.
• After applying a coverslip, the slide is observed under a microscope.
• Key structures such as the cytoplasm, cell membrane, and nucleus of the cheek cells are visible.

Observing Cells: Experiment with Leaf Cells

• A Rheo leaf is taken, water is added, and it's covered with a slide for observation.
• Saffron stain is used to produce a more vivid colour during observation.
• Structural components like the cell wall, chloroplasts, and nucleus can be seen in plant cells using this method.

Observing Cells: Experiment with Blood Cells

• White blood cells can be observed through a slide, but it requires care.
• Prepared slides of blood cells show disc-shaped red blood cells and irregular white blood cells; white blood cells can be stained for clarity.
• Procedure: A finger is pricked, a blood drop is put on a slide, covered with another slide, and observed under a microscope without staining for clear cell viewing.

Closing Points

• Cells have the ability to perform chemical activities
• Topic review request for the following video
• Channel subscription request