Introduction to Cells: Structure, Types, and Organelles

Teoria Celular (Cell Theory)

Principles of Cell Theory

The cell theory is a foundational concept in biology, describing the properties and significance of cells in living organisms.

• All living beings are formed by cells.

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

• All cells arise from pre-existing cells.

Exception: Viruses are considered acellular (not made of cells) and are an exception to cell theory.

Partes Básicas da Célula (Basic Parts of the Cell)

Essential Cell Components

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

• Membrana plasmática (Plasma membrane): A selective barrier that surrounds the cell, controlling the movement of substances in and out.

• Citoplasma (Cytoplasm): The jelly-like substance within the cell where organelles are suspended and metabolic reactions occur.

• Material genético (Genetic material): DNA or RNA that carries the genetic instructions for the cell's activities.

Tipos de Células (Types of Cells)

Procarionte vs. Eucarionte (Prokaryotic vs. Eukaryotic Cells)

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

• Procarionte (Prokaryotic): Cells without a true nucleus; genetic material is not enclosed by a membrane. Example: Bacteria.

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

Sem núcleo: Prokaryotes Com núcleo: Eukaryotes

Organelas Celulares (Cell Organelles)

Main Organelles and Their Functions

Organelles are specialized structures within cells that perform distinct processes necessary for cellular life:

• 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 out of the cell.

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

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

• Vacuolo (Vacuole): Stores nutrients, waste products, and helps maintain turgor pressure in plant cells.

Comparação: Célula Vegetal vs. Célula Animal (Plant Cell vs. Animal Cell)

Key Differences

• 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 image provides a visual summary of these concepts, including diagrams of plant and animal cells, and highlights the exception of viruses to cell theory.