Cytomembrane System: Structure and Function

• The cytomembrane system is a network of membranes and organelles.
• It modifies, packages, and transports lipids and proteins, altering and sorting them in the process.
• It is found in eukaryotic cells.
• It is also called the endomembrane system.
• The cytomembrane system is essential for maintaining the structure and function of a eukaryotic cell.
• The cytomembrane system is composed of the Endoplasmic Reticulum, Golgi Bodies, Vesicles, and the Nuclear Envelope.

Parts of the Cytomembrane System

• The endoplasmic reticulum is the site where polypeptide chains are modified
• It has two types, rough and smooth.

Rough ER

• It is a protein factory for cells.
• It distributes vesicles.

Smooth ER

• It synthesizes lipids and metabolizes carbohydrates
• It detoxifies drugs and poisons, and stores calcium ions.

Golgi Bodies

• Golgi bodies process and package proteins produced in the rough endoplasmic reticulum.
• The Golgi apparatus modifies the products of the ER.
• It manufactures certain macromolecules and sorts and packages materials into transport vesicles.

Vesicles

• They are compartments formed by a lipid bilayer.
• They separate contents from the cytoplasm or a fluid-based extracellular environment.

Lysosomes

• They bud from Golgi bodies
• Lysosomes take part in intracellular digestion and contain powerful enzymes.
• These enzymes can break down carbohydrates, proteins, nucleic acids, and lipids.
• They break down worn-out cell parts or molecules so they can be used to build new cellular structures.

Peroxisomes

• They contain enzymes that digest fatty acids and amino acids.
• They break down hydrogen peroxide, a toxic byproduct of fatty acid metabolism.
• They convert hydrogen peroxide to water and oxygen, or use it in reactions that break down alcohol and other toxins.

Functions of the Cytomembrane System

• Protein Synthesis and Secretion
• Lipid & Steroid Synthesis
• Detoxification
• Calcium Storage & Signaling
• Modification & Sorting of Proteins
• Recycling of Cellular Components

The Cytoskeleton

• The cytoskeleton is a network of proteins within a cell.
• It provides structure and support and enables movement and division.
• It is made of proteins that provide mechanical support to the cell and its cytoplasmic constituents
• Cytoskeletons consist of three major classes of elements

Types of Fibers

Microfilaments:

• They are also known as actin filaments
• Microfilaments have a diameter of 7 nm and are involved in cellular movement.
• They consist of two intertwined strands of a globular protein called actin.
• They provide rigidity and shape to the cell

Intermediate Filaments:

• They consist of several intertwined strands of fibrous proteins and have a diameter of 8-10 nm.
• Their function is purely structural.
• They bear tension, thus maintaining the shape of the cell.
• They anchor the nucleus and other organelles in place.
• Intermediate filaments area diverse group of cytoskeletal elements.

Microtubules:

• They are small, hollow tubes.
• Their walls consist of 13 polymerized dimers of α-tubulin and β-tubulin.
• They are structural elements of flagella, cilia, and centrioles and have a diameter of 25 nm.

Functions of the Cytoskeleton

• Gives cells their shape and organizes the cytoplasm.
• Allows cells to move.
• Regulates cell division.
• Transports materials and organelles within the cell.
• Allows cells to adhere to other cells and communicate with other cells.

The cytomembrane system, also known as the endomembrane system, is a network of membranes and organelles found in eukaryotic cells. It modifies, packages, and transports lipids and proteins. The cytomembrane system is composed of the Endoplasmic Reticulum, Golgi Bodies, Vesicles, and the Nuclear Envelope.