Células (Cells)

Teoria Celular (Cell Theory)

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

• All living beings are formed by cells.

• Cells are the basic morphological and functional units of living organisms.

• All cells arise from pre-existing cells.

Exception: Viruses are considered acellular because they do not have a cellular structure and cannot carry out life processes independently.

Partes Básicas da Célula (Basic Parts of the Cell)

All cells share certain fundamental structures:

• Membrana plasmática (Plasma membrane): The outer boundary that controls the movement of substances in and out of the cell.

• Citoplasma (Cytoplasm): The jelly-like substance inside the cell where organelles are suspended.

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

Tipos de Células (Types of Cells)

• Procarionte (Prokaryotic): Cells without a defined nucleus. Their genetic material is not enclosed within a membrane. Example: Bacteria.

• Eucarionte (Eukaryotic): Cells with a true nucleus, where the genetic material is enclosed by a nuclear membrane. Examples: Plant and animal cells.

Organelas Celulares (Cell Organelles)

Organelles are specialized structures within cells that perform distinct processes. Main organelles include:

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

• Ribossomo (Ribosome): Responsible for protein synthesis.

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

• Complexo golgiense (Golgi apparatus): Modifies, sorts, and packages proteins and lipids for storage or transport.

• Lisossomo (Lysosome): Contains digestive enzymes to break down waste.

• Centríolo (Centriole): Involved in cell division in animal cells.

• Vacuolo (Vacuole): Stores nutrients, waste products, and helps maintain cell structure (large in plant cells).

Diferenças entre Célula Vegetal e Célula Animal (Differences Between Plant and Animal Cells)

• Célula Vegetal (Plant Cell): Has 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.

Example: Plant cells can perform photosynthesis due to the presence of chloroplasts, while animal cells cannot.

Additional info: The plasma membrane is composed mainly of a phospholipid bilayer with embedded proteins, which allows selective permeability. The cell wall in plants provides structural support and protection.