Cell Theory and Characteristics

The Cell Theory

• All living organisms consist of one or more cells.
• Cells serve as the fundamental units of structure, function, and organization in living organisms.
• New cells arise from pre-existing cells through cell division.

Modern Principles of Cell Theory

• All living beings are composed of cells.
• Cells are the basic structural and functional units of all organisms.
• Cells originate from pre-existing cells through division.
• The overall activity of an organism is the cumulative activity of its individual cells.
• Energy flow essential for life occurs within cells.
• Cells contain hereditary information, passed from one generation to the next during division.
• Similar species have chemically comparable cell compositions.

Cell Characteristics

• Cell Number: Varies across different organisms; multicellular organisms consist of many cells, while unicellular organisms consist of one.
• Cell Shape: Diverse shapes tailored to their specific functions (e.g., neurons, muscle cells).
• Cell Size: Cells can dramatically range in size from microscopic bacteria to visible egg cells.

Functions of a Cell

• Structure and Support: Cells provide structural frameworks; specialized cells like collenchyma and sclerenchyma contribute to physical support.
• Growth: Cellular division (mitosis) enables tissue growth in complex organisms.
• Transport: Cells manage the intake of nutrients and the expulsion of wastes through passive and active transport mechanisms.
• Energy Production: Metabolic processes within cells enable energy production required for life.
• Reproduction: Cellular processes facilitate reproduction via mitosis and meiosis.

Key Cell Components

• Nucleus: The control center of the cell, usually centrally located; responsible for cell division and housing DNA, surrounded by a nuclear membrane.
• Cytoplasm: The gel-like material between the nucleus and plasma membrane where organelles are found.
• Cell (Plasma) Membrane: A semipermeable membrane that regulates the exchange of materials in and out of the cell; composed of lipids, proteins, and carbohydrates.

Types of Cells

• Eukaryotic Cells:

  • DNA is located in a membrane-bound nucleus.
  • Contains specialized organelles within the cytoplasm.
  • Includes organisms like protists, fungi, plants, and animals (Domain Eukarya).

• Prokaryotic Cells:

  • DNA is found in a non-membrane-bound area called the nucleoid.
  • Typically smaller and simpler than eukaryotic cells.

Explore the fundamentals of cell theory and the characteristics that define living organisms. This quiz covers the modern principles of cell theory, detailing how cells function, organize, and divide. Understand the significance of cellular structure in the context of life.