Teoria Celular (Cell Theory)

Principles of Cell Theory

The cell theory is a fundamental concept in biology that describes the properties of cells, the basic unit of life. It is based on three main principles:

• All living beings are formed by cells.

• Cells are the smallest morphological and functional units of life.

• All cells arise from pre-existing cells.

Exception: Viruses are considered acellular entities because they lack cellular structure and only exhibit life-like properties inside host cells.

Partes Básicas da Célula (Basic Parts of the Cell)

Essential Cell Components

All cells, regardless of type, share certain basic structures:

• Plasma Membrane: A selective barrier that encloses the cell, controlling the movement of substances in and out.

• Cytoplasm: The jelly-like substance within the cell, containing organelles and the cytosol.

• Genetic Material: DNA or RNA that carries hereditary information and instructions for cellular activities.

Tipos de Células (Types of Cells)

Prokaryotic vs. Eukaryotic Cells

Cells are classified based on the presence or absence of a defined nucleus:

• Prokaryotic Cells: Do not have a membrane-bound nucleus. Genetic material is found in the nucleoid region. Example: Bacteria.

• Eukaryotic Cells: Possess a true nucleus enclosed by a nuclear membrane. Examples: Animal and Plant cells.

With Nucleus: Eukaryotes Without Nucleus: Prokaryotes

Organelas Celulares (Cell Organelles)

Main Organelles and Their Functions

Organelles are specialized structures within cells that perform distinct processes:

• Mitochondria: Site of cellular respiration and energy (ATP) production.

• Ribosomes: Responsible for protein synthesis.

• Endoplasmic Reticulum (ER): Involved in protein and lipid synthesis; can be rough (with ribosomes) or smooth (without ribosomes).

• Golgi Complex: Modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

• Lysosomes: Contain digestive enzymes to break down waste materials and cellular debris.

• Centrioles: Involved in cell division in animal cells.

• Vacuoles: Storage organelles, larger in plant cells for water and nutrient storage.

Tipos de Células Eucarióticas (Types of Eukaryotic Cells)

Animal vs. Plant Cells

• Animal Cells: Typically round, lack a cell wall and chloroplasts, contain centrioles.

• Plant Cells: Have a rigid cell wall, chloroplasts for photosynthesis, and a large central vacuole.

Example: Human skin cells (animal cell), leaf cells (plant cell).

Additional info: The image provides a visual summary of cell theory, basic cell parts, organelles, and the distinction between prokaryotic and eukaryotic cells, as well as animal and plant cells.