Cell Structure and Function: Components and Processes

Cell Structure and Function

Key Components of the Cell

The cell is the basic unit of life, and it is composed of several essential components:

• Cell Membrane: A thin layer surrounding the cell, forming the boundary between the cell and its surrounding environment, the extracellular medium.
• Cytoplasm: The substance of the cell, excluding the nucleus. It is formed by a water-rich solution in which a variety of structures, called organelles, are dispersed. These organelles are responsible for carrying out the different functions of the cell.
• Cellular Nucleus: A structure that is usually spherical and located in the center of the cell. It contains the genetic material with the necessary information to direct and control cellular functions.
• Mitochondria: Oval-shaped organelles with a double membrane delimiting an interior space. They provide energy for the cell to function.
• Vacuoles: Membranous vesicles containing water with dissolved substances, stored reserves, or waste products.
• Lysosomes: Membrane vesicles inside which complex substances are transformed into simpler ones that the cell can use.
• Cytoskeleton: A set of filaments that are distributed, forming a network throughout the cytoplasm. It forms the "skeleton" of the cell and is involved in cell movement.
• Centrioles: Two hollow cylinders whose walls are formed by filaments. They direct the movement of the cytoskeleton.
• Golgi Apparatus: Consists of stacks of flattened membranous sacs surrounded by small sacs or vesicles. These vesicles package substances manufactured in the reticulum and often release their contents into the extracellular medium. Its main function is secretion.
• Ribosomes: Small particles that are found both free in the cytoplasm and attached to the membranes of the endoplasmic reticulum. They are responsible for producing proteins.
• Endoplasmic Reticulum: A set of membranous sacs and interconnected channels extending throughout the cytoplasm. The reticulum manufactures various substances, such as proteins or lipids. There are two types:
  • Rough Endoplasmic Reticulum: With ribosomes attached to the outside of its membrane.
  • Smooth Endoplasmic Reticulum: Without attached ribosomes.

Eukaryotic Cells

Eukaryotic cells are characterized by having their nucleus isolated from the rest of the cytoplasm and by having their cytoplasm compartmentalized into organelles.

Structure of the Nucleus

• Nuclear Envelope: A double membrane pierced by pores that permit the exchange of substances between the nucleus and cytoplasm.
• Nucleoplasm: The content of the nucleus. It is formed by a solution containing chromatin and nucleoli.
• Chromatin: A set of very long filaments that are clustered inside the nucleus. Each strand is formed by a molecule of DNA (deoxyribonucleic acid) that contains the genetic information.
• Nucleoli: These are areas within the nucleus where ribosomes are manufactured.

Cellular Processes

• Diffusion: A mechanism by which some small molecules cross the cell membrane. Molecules move from an area of higher concentration to an area of lower concentration.
• Osmosis: The diffusion of water through a membrane from a dilute solution to a more concentrated one.
• Active Transport: The cell needs substances that are found in lesser concentration in the extracellular medium than inside. This requires energy.
• Endocytosis: The membrane collapses and engulfs the particle.
• Exocytosis: Cellular vesicles discharge their contents outside the cell.
• Catabolism: A set of reactions whose objective is to degrade and transform complex molecules into simpler ones to release energy.
• Anabolism: A set of reactions whose goal is to build complex molecules from simpler ones. This requires energy.