Recording-2025-02-24T19:05:54.446Z

Endoplasmic Reticulum (ER)

• Definition:

  • The term 'endoplasmic' refers to 'inside the cytoplasm' and 'reticula' means 'little net'.

  • Described as small net-like structures observed under a microscope, now recognized as a series of tubes that function like a sewer system inside the cell.

Rough Endoplasmic Reticulum (Rough ER)

• Characteristics:

  • Named 'rough' due to the presence of ribosomes on its surface, which appear as brownish blobs in electron microscope images.

  • Ribosomes dock on the Rough ER's ports, facilitating protein synthesis.

• Function:

  • Ribosomes synthesize proteins, which are then deposited into the Rough ER for processing.

  • Responsible for the proper folding of proteins; cells heavily involved in protein production have an abundance of ribosomes and Rough ER.

Smooth Endoplasmic Reticulum (Smooth ER)

• Characteristics:

  • Lacks ribosomes, resulting in a smooth appearance under an electron microscope.

  • Found in specific cells, such as:

    • Ovarian cells producing estrogen.

    • Testicular cells producing testosterone.

    • Liver cells filled with detoxification enzymes.

• Function:

  • Smooth ER plays a key role in detoxifying substances that enter the body through the digestive system.

  • These substances are processed and monitored before reaching vital organs (e.g., brain).

  • In heavy drinkers, liver cells (hepatocytes) accumulate Smooth ER, leading to potential dysfunction as other organelles are crowded out.

Golgi Apparatus

• Overview:

  • Sometimes called Golgi complex, it is involved in modifying, sorting, and shipping proteins and other molecules received from the ER.

• Process:

  • Preprocessed products from the Rough and Smooth ER are transported to the Golgi for further modification.

  • Example: Insulin synthesis begins in the Rough ER as preinsulin, which is a large molecule with an active hormone segment.

  • The preinsulin moves through various compartments of the Golgi, undergoing modifications in different pH and enzymatic conditions.

• Structure:

  • Composed of layers analogous to flat pita breads, with vesicles exiting the trans face after sorting and modification.

  • The cyst face of the Golgi faces the ER, while the trans face is aligned with the secretion pathway.

• Final Export:

  • Once fully modified, insulin is encapsulated in a vesicle and released into the bloodstream to function as a hormone.

Lysosomes

• Overview:

  • Lysosomes are considered the digestive organelles of the cell, containing hydrolytic enzymes that promote hydrolysis reactions.

• Functionality:

  • Lysosomes can digest proteins (proteases), carbohydrates (carbohydrases), and nucleic acids (nucleases) by breaking down their respective biomolecules.

  • If an organelle, like a malfunctioning mitochondrion, is detected, lysosomes fuse with its vesicle to digest it into basic components (amino acids, monosaccharides, etc.) for reuse.

  • Primarily involved in the immune response by breaking down dead cells and debris in the body.

Vacuoles and Vesicles

• Overview:

  • Vacuoles in plant cells and vesicles in animal cells are membrane-bound storage sacs within the cytoplasm.

• Plant Cells:

  • Plants possess a large central vacuole that stores nitrogenous waste, which prevents the buildup of toxins.

  • As the concentration of solutes increases within the vacuole, water rushes in and helps maintain turgor pressure, allowing plants to stand upright against gravity.

• Function in Water Regulation:

  • Certain protozoa have contractile vacuoles that act like a bilge pump to expel excess water from inside the cell, thus preventing it from bursting due to increased internal pressure.

• Importance:

  • Though not as dynamic as other organelles, vacuoles and vesicles play crucial roles in storage and maintenance of cell stability, particularly in plants and protozoa.