La célula :: Biología y Geología, 1° ESO

Understanding Cells: The Building Blocks of Life

Introduction to Cells

• The lesson begins by highlighting the diversity of life in the biosphere, focusing on what all living beings have in common: they are made up of cells.

• Cells are described as the smallest units that form living organisms, comparable in size to a microchip used in electronic devices.

Observing Cells

• To observe cells, a microscope is necessary; cells require their own unit of measurement, the micrometer (micra), which is one-thousandth of a millimeter.

• A human hair has a diameter of approximately 80 micrometers, illustrating how small cells can be.

Common Characteristics of Cells

• All cells share three common characteristics:

• They contain DNA molecules that regulate internal processes.

• They are surrounded by a plasma membrane that separates them from their environment.

• They contain cytoplasm, a viscous liquid where cellular organelles reside.

Types of Cells

Prokaryotic vs. Eukaryotic Cells

• There are two main classifications for cells: prokaryotic and eukaryotic.

• Prokaryotic cells lack a nucleus; their DNA is dispersed throughout the cytoplasm.

• Eukaryotic cells have a defined nucleus containing all cellular DNA protected by a nuclear membrane.

Organelles in Eukaryotic Cells

• Key organelles found in eukaryotic cells include:

• Mitochondria

• Lysosomes

• Endoplasmic reticulum

• Golgi apparatus

• Ribosomes

• Vacuoles

Differences Between Animal and Plant Cells

• Eukaryotic cells can be further divided into animal and plant types:

• Animal cells tend to be more circular.

• Plant cells have chloroplasts for photosynthesis and rigid cell walls made from cellulose.

Unique Features and Fun Facts about Cells

• Animal cells uniquely possess centrioles, cylindrical organelles involved in cell division.

• Viruses are not considered living organisms because they lack cellular structure and do not perform vital functions like nutrition or reproduction. Their existence relies on infecting host cells.

Conclusion