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.

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