Cell Basics and Structures

Cell Basics

• All living organisms are composed of cells
• Cells originate from pre-existing cells.
• The cell is the fundamental unit of life.
• Cells are classified into two main categories: prokaryotic and eukaryotic.

Prokaryotic Cells

• Lack a true nucleus and membrane-bound organelles.
• Examples include bacteria.
• They are unicellular, comprised of a single cell.

Eukaryotic Cells

• Have a true nucleus and membrane-bound organelles.
• Include both multicellular organisms (animals and plants) and some single-celled organisms.

Cell Structures:

• Plasma membrane: A thin membrane surrounding cells and organelles, playing a vital role in regulating what enters and exits.
• Cytoplasm: Gel-like substance containing chemicals and organelles, supporting metabolic reactions, organelle movement, and structural support.
• Nucleus: The control center enclosed by a membrane, containing DNA, providing instructions for protein production and cell functions. It's crucial for cell division.
• Ribosomes: These are like construction workers, building proteins.
• Endoplasmic reticulum (ER): Functions as a manufacturing and packaging system, working with the Golgi apparatus and ribosomes. It produces and transports lipids, and packages proteins.
• Golgi apparatus: Also known as the Golgi complex, Golgi body, or simply the Golgi. It's the packaging organelle and packages vesicles.
• Lysosomes: Also known as "little digestion machines," they break down food particles, waste, and foreign substances within the cell.
• Centrioles: Found in animal cells, they help in cell division.

Plant Cell Specific Structures

• Cell wall: Made of cellulose, it provides structural support for plant cells.
• Chloroplasts: These are the food producers, carrying out photosynthesis.

Compound Microscope Components

• Stage clips: Hold slides in place during viewing.
• Illuminator: Provides light for viewing, replacing the traditional mirror.
• Diaphragm (also known as the iris): Controls the amount of light that reaches the specimen.
• Base: Offers stability, houses the light source, and provides a platform for microscope placement.
• Eyepiece: Contains the lens used for viewing, allowing comfortable observation.
• Body Tube: Holds the objective lenses and eyepiece at a fixed distance for proper viewing.
• Coarse Focus Knob: Moves the stage to bring the specimen into initial focus.
• Fine Focus knob: Refines the focus, often located within the coarse focus knob, for sharp viewing under different power levels.
• Objective Lenses: Magnify the specimen for detailed observation, ranging from 4x to 100x magnification.
• Body Tube: Holds the objective lenses and eyepiece in proper alignment.
• Revolving Nosepiece: Holds the objective lenses and allows rotation to select different magnifications.
• Arm: Connects the microscope head to the base, providing stability.
• Specimen Stage: Platform where the slide is placed for viewing.

Cell Theory

• Matthias Schleiden (1838): discovered that plants were made of cells through extensive microscopic observation.
• Theodor Schwann (1839): expanded Schleiden’s findings to animals, concluding that all living things are made of cells through his own microscopic studies.
• Rudolf Virchow (1858): proposed the principle that new cells arise from pre-existing cells, forming the second part of the cell theory.

Summary of Cell Theory

• All living organisms are composed of cells.
• All cells come from pre-existing cells.
• The cell is the fundamental unit of life.

Explore the fundamental concepts of cell biology, including the differences between prokaryotic and eukaryotic cells. Learn about essential cell structures such as the plasma membrane, cytoplasm, and nucleus that are vital for cellular functions and organism life. Test your understanding of these foundational topics.