Células (Cells)

Teoria Celular (Cell Theory)

The cell theory is a fundamental concept in biology, describing the properties and significance of cells as the basic unit of life.

• All living beings are formed by cells: Every organism is composed of one or more cells.

• Cells are the basic morphological and functional units: Cells carry out essential life processes.

• Cells originate from other cells: New cells are produced by the division of pre-existing cells.

• Exception: Viruses: Viruses are considered acellular and do not fit the classical cell theory.

Partes Básicas da Célula (Basic Parts of the Cell)

All cells share certain fundamental structures that are essential for their function and survival.

• Membrana plasmática (Plasma membrane): The boundary that separates the cell from its environment and regulates the movement of substances in and out.

• Citoplasma (Cytoplasm): The internal fluid of the cell where organelles are suspended and metabolic reactions occur.

• Material genético (Genetic material): DNA or RNA that carries the instructions for cell function and reproduction.

Classificação das Células (Classification of Cells)

Cells are classified based on the presence or absence of a nucleus and their structural complexity.

• Sem núcleo (Without nucleus): Procarionte (Prokaryotic) - Cells lacking a defined nucleus; genetic material is not enclosed within a membrane. Example: Bacteria.

• Com núcleo (With nucleus): Eucarionte (Eukaryotic) - Cells with a true nucleus, where genetic material is enclosed by a nuclear membrane. Examples: Animal and plant cells.

Organelas Celulares (Cell Organelles)

Organelles are specialized structures within cells that perform distinct functions necessary for cellular life.

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

• Ribossomo (Ribosome): Responsible for protein synthesis.

• Retículo endoplasmático (Endoplasmic reticulum): Involved in protein and lipid synthesis.

• Complexo golgiense (Golgi complex): Modifies, sorts, and packages proteins and lipids for secretion or use within the cell.

• Lisossomo (Lysosome): Contains digestive enzymes for breaking down waste materials and cellular debris.

• Centriolo (Centriole): Important for cell division in animal cells.

• Vacuolo (Vacuole): Stores nutrients and waste products; prominent in plant cells.

Tipos de Células (Types of Cells)

Cells can be further distinguished based on their structure and function.

• Célula Vegetal (Plant Cell): Contains a cell wall, chloroplasts for photosynthesis, and a large central vacuole.

• Célula Animal (Animal Cell): Lacks a cell wall and chloroplasts, but contains centrioles and smaller vacuoles.

Comparação: Célula Vegetal vs. Célula Animal

The following table summarizes the main differences between plant and animal cells:

Additional info:

• Prokaryotic cells are generally smaller and simpler than eukaryotic cells.

• Viruses, although they contain genetic material, lack cellular structure and are not considered living cells.