Recording-2025-02-19T16:07:29.050Z

Endomembrane System Overview

• The endomembrane system includes all membranes within the cell, such as:

  • Nuclear membrane: Double membrane surrounding the nucleus, contiguous with the endoplasmic reticulum (ER).

  • Endoplasmic Reticulum (ER): Networks of membranes involved in protein and lipid synthesis.

  • Golgi apparatus: Membrane-bound organelle known for modifying, sorting, and packaging proteins and lipids for secretion.

  • Plasma membrane: Outer boundary of the cell that regulates what enters and exits.

Endoplasmic Reticulum (ER)

• Two types of ER:

  • Rough ER:

    • Studded with ribosomes, synthesizes proteins.

    • Proteins are modified (e.g., glycosylation) as they enter the ER.

  • Smooth ER:

    • Lacks ribosomes, involved in:

      • Lipid synthesis.

      • Carbohydrate metabolism.

      • Detoxification processes.

      • Storage of ions, particularly calcium (Ca2+).

Function of Rough and Smooth ER

• Rough ER synthesizes and modifies proteins, producing vesicles for transport.

• Smooth ER detoxifies harmful substances and synthesizes lipids, acting as storage and transport.

Golgi Apparatus

• Composed of stacked membrane-bound structures known as cisternae.

• Functions include:

  • Receiving proteins and lipids from the ER at the cis face.

  • Modifying them (glycoprotein formation) and sending them out from the trans face.

  • Packaging molecules into vesicles for secretion or delivery to different cell locations.

Vesicle Transportation

• Vesicles serve as transport vehicles, moving materials between ER, Golgi, and plasma membrane.

• Their movement is facilitated by microtubules, analogous to a delivery system or highway network in a cell.

Secretion Process

• Proteins like insulin are synthesized in the rough ER, processed in the Golgi, and ultimately secreted via vesicles at the plasma membrane.

• The Golgi apparatus modifies proteins (e.g., attaching carbohydrates) and sorts them for proper delivery.

Cytoskeleton

• Provides structural support and shape to the cell, helping organize organelles.

• Consists of three components:

  • Microtubules: Hollow rods made from tubulin, involved in maintaining cell shape, transport, and cell division.

  • Microfilaments: Thin strands of actin, responsible for motility and changing cell shape.

  • Intermediate Filaments: Fibrous proteins (e.g., keratin) providing mechanical support and anchoring organelles.

Key Functions of Cytoskeletal Components

• Microtubules:

  • Facilitate movement of organelles and are crucial for mitosis and meiosis.

  • Structure allows for dynamic changes in cell shape.

• Microfilaments:

  • Help in muscle contraction and are important for cytokinesis in cell division.

• Intermediate Filaments:

  • Provide stability and support, anchoring the nucleus.

Extracellular Matrix (ECM)

• Composed of proteins and carbohydrates, it connects cells and facilitates communication.

• Integrins link ECM components to the cytoskeleton, aiding in cell attachment and signaling.

• The ECM plays a role in tissue formation by keeping cells together, such as skin and liver tissue.

Communication in Tissues

• Cellular communication is essential for maintaining tissue structure and function.

• Cells use protein tags to recognize each other and adhere appropriately, promoting tissue integrity.

Summary

• The endomembrane system is crucial for the secretion, synthesis, transport, and modification of molecules within the cell.

• The cytoskeleton supports cellular structure and facilitates movement.

• The extracellular matrix enables cell communication and adhesion, essential for forming functional tissues.