Cell Biology Essentials: Theory, Organization, and Cell Types

Cell Theory Fundamentals

• The Cell as the Structural Unit: All living beings are composed of one or more cells.
• The Cell as the Functional Unit: Cells perform all metabolic processes essential for life.
• All Cells Arise from Pre-existing Cells: Cells originate from the division of other cells.
• The Cell as the Genetic Unit: Cells contain the hereditary information of all living beings.

Biological Levels of Organization

Abiotic Levels:

• Subatomic Particles: Elementary particles that form atoms.
• Atoms: The smallest part of a chemical element.
• Molecules: A combination of two or more identical or different atoms.
• Macromolecules: The union of several molecules.
• Organelles: The union of supramolecular structures forming a complex cellular structure with a determined function.

Biotic Levels:

• Cells: The anatomical and functional unit of life.
• Tissues: A group of cells performing a specific function.
• Organs: The union of different tissues with a specific role.
• Organ Systems: A group of organs performing a specific function.
• Individual: An organism composed of several organ systems.
• Population: A group of individuals of the same species.
• Community: A group of populations sharing the same space.
• Ecosystem: A group of communities, along with their relationships with the environment.
• Ecosphere: A group of ecosystems that form the Earth.

Plant vs. Animal Cell Differences

• Cell Wall: Both plant and animal cells possess a cell membrane. However, plant cells also have a rigid cellulose cell wall, which provides structural support and rigidity. Animal cells lack a cell wall, having only a cytoplasmic membrane.
• Chloroplasts and Photosynthesis: Plant cells contain chloroplasts, organelles capable of synthesizing sugars from carbon dioxide, water, and sunlight (photosynthesis). This makes plants autotrophs, meaning they produce their own food. Animal cells lack chloroplasts and therefore cannot perform photosynthesis.
• Vacuoles: Plant cells typically have a single, large, fluid-filled vacuole that occupies most of their interior, storing water, nutrients, and waste. In contrast, animal cells usually have many smaller vacuoles.
• Reproduction: Plant cells can replicate through asexual reproduction, resulting in cells identical to the progenitor cells. Animal cells are capable of sexual reproduction.