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  • ICAR and TNAU E-Course Summarized

    Summarized Notes
  • Which of the following statements is correct about endoplasmic reticulum?✔ I. It is a large network of membrane-bound tubes and sheets.✔ II. It is similar in structure to the plasma membrane.

    Question: Which of the following statements is correct about endoplasmic reticulum?✔ I. It is a large network of membrane-bound tubes and sheets.✔ II. It is similar in structure to the plasma membrane.

    Options:

    Only I
    Only II
    Neither I nor II
    Both I and II

    🔑Key Points:

    • Endoplasmic reticulum:
    The network or reticulum of tiny tubular structures scattered in the cytoplasm is called the endoplasmic reticulum (ER).
    The ER divides the intracellular space into two distinct compartments, i.e., luminal (inside ER) and extraluminal (cytoplasm) compartments.
    The ER is of two types based on the presence or absence of ribosomes on its surface.
    The Endoplasmic reticulum bearing ribosomes on their surface is called Rough Endoplasmic Reticulum (RER) whereas in the absence of the ribosomes they appear smooth and are called Smooth Endoplasmic Reticulum (SER).​
    The smooth endoplasmic reticulum (smooth ER) is a membranous organelle found in most eukaryotic cells. Its functions include 
    Synthesis of Lipids, including cholesterol and phospholipids.
    Steroid Hormones.
    Storage and metabolism of calcium ions within the cell.
    Detoxification of harmful metabolic byproducts/toxic substances.
    Glycogenolysis i.e the breakdown of the molecule glycogen into glucose.

    🔴Additional Information:
    Plasma membrane
    Plasma membrane, also called the cell membrane is mainly composed of lipids and proteins.
    The major lipids are arranged in a bilayer and are called phospholipids.
    The plasma membrane also contains cholesterol.
    Cell membranes also possess protein and carbohydrates as per Biochemical investigation.
    The ratio of lipids and proteins varies in different cell types.
    For example, in human beings, the membrane of the erythrocyte has approx 40 per cent lipids and 52 per cent protein.

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