Line 1: Camillo Golgi (1898) first observed densely stained reticular structures near the nucleus.
Explanation: This line introduces the historical context by mentioning Camillo Golgi, who first observed these structures in 1898. These structures were later named Golgi bodies or Golgi apparatus after him. Enrichment: Early microscopes did not have the resolution to see organelles in detail. Golgi used special staining techniques to reveal these structures near the nucleus.
Line 2: These were later named Golgi bodies after him.
Explanation: This line clarifies the current terminology used for these structures – the Golgi apparatus.
Line 3: They consist of many flat, disc-shaped sacs or cisternae of 0.5µm to 1.0µm diameter (Figure 8.6).
Explanation: This line describes the basic structure of the Golgi apparatus. It is made up of numerous flattened, stacked sacs called cisternae (singular: cisterna). Enrichment: Each cisterna is roughly 0.5 to 1 micrometer (µm) in diameter. You can imagine them as a stack of plates. (Figure 8.6 would visually show this structure, but it’s not included here).
Line 4: These are stacked parallel to each other.
Explanation: This line elaborates on the arrangement of the cisternae. They are not randomly distributed but lie flat and parallel to each other, forming a stacked structure.
Line 5: Varied number of cisternae are present in a Golgi complex.
Explanation: This line highlights the variability. Unlike some organelles with a fixed number of components, the Golgi apparatus can have a different number of cisternae depending on the cell’s needs.
Line 6: The Golgi cisternae are concentrically arranged near the nucleus with distinct convex cis or the forming face and concave trans or the maturing face.
Explanation: This line describes the specific arrangement of the cisternae: Concentric: Arranged in a roughly circular fashion around the nucleus. Cis Face: The convex (outward-curving) side is called the cis face, also known as the forming face. This is where materials first enter the Golgi apparatus. Trans Face: The concave (inward-curving) side is called the trans face, also known as the maturing face. This is where processed materials exit the Golgi apparatus. Enrichment: Imagine a stack of plates with a designated “in” and “out” side. Materials travel through the Golgi apparatus from the cis (in) face to the trans (out) face for processing and packaging.
Line 7: The cis and the trans faces of the organelle are entirely different, but interconnected.
Explanation: This line emphasizes the functional distinction between the cis and trans faces. While separate, they are still connected within the Golgi apparatus. Enrichment: The cis face interacts with incoming transport vesicles from the ER, while the trans face is responsible for packaging and releasing processed materials.
Line 8: The golgi apparatus principally performs the function of packaging materials, to be delivered either to the intra-cellular targets or secreted outside the cell.
Explanation: This line introduces the primary function of the Golgi apparatus – packaging of materials. Enrichment: The Golgi apparatus receives various molecules, modifies them as needed, and packages them into vesicles for specific destinations within the cell or for secretion outside the cell.
Line 9: Materials to be packaged in the form of vesicles from the ER fuse with the cis face of the golgi apparatus and move towards the maturing face.
Explanation: This line describes the first step in the packaging process. Vesicles containing materials bud off from the ER and fuse with the cis face of the Golgi apparatus. These materials then progress through the stacked cisternae towards the trans face. Enrichment: Imagine packages being received at a processing center (Golgi apparatus) from a warehouse (ER). These packages are then sorted and potentially modified before being shipped out (released from the trans face).
Line 10: This explains, why the golgi apparatus remains in close association with the endoplasmic reticulum.
Explanation: This line explains the reason for the close physical proximity of the Golgi apparatus to the ER. They are functionally linked, with the ER supplying materials for processing and packaging in the Golgi apparatus.
Line 11: A number of proteins synthesised by ribosomes on the endoplasmic reticulum are modified in the cisternae of the golgi apparatus before they are released from its trans face.
Explanation: This line elaborates on the processing that occurs within the Golgi apparatus. Proteins synthesized on the ER ribosomes are often further modified (e.g., addition of sugar molecules) within the Golgi cisternae before their final release. Enrichment: These modifications can affect a protein’s function, stability, or destination within the cell. The Golgi apparatus acts like a quality control and sorting station for proteins.
Line 12: Golgi apparatus is the important site of formation of glycoproteins and glycolipids.
Explanation: This line highlights the Golgi apparatus’ role in creating specific types of molecules: Glycoproteins: Proteins with attached sugar molecules. Glycolipids: Lipids (fats) with attached sugar molecules. Enrichment: These modifications can play a role in cell-to-cell communication, recognition, and targeting of molecules to specific locations within or outside the cell.
Line 1: Lysosomes: These are membrane bound vesicular structures formed by the process of packaging in the golgi apparatus.
Explanation: This line introduces lysosomes as membrane-bound sacs formed by the Golgi apparatus. Enrichment: Recall that the Golgi apparatus packages various materials. Lysosomes are a specialized type of vesicle containing digestive enzymes.
Line 2: The isolated lysosomal vesicles have been found to be very rich in almost all types of hydrolytic enzymes (hydrolases – lipases, proteases, carbohydrases) optimally active at the acidic pH.
Explanation: This line elaborates on the content of lysosomes. They are filled with hydrolytic enzymes (enzymes that break down large molecules) of various types: Lipases: Break down fats (lipids). Proteases: Break down proteins. Carbohydrases: Break down carbohydrates. Enrichment: These enzymes are most active in an acidic environment (low pH) maintained within the lysosome.
Line 3: These enzymes are capable of digesting carbohydrates, proteins, lipids and nucleic acids.
Explanation: This line emphasizes the versatility of lysosomal enzymes. They can break down a wide range of biological molecules. Enrichment: Imagine lysosomes as tiny cellular recycling centers with a diverse set of enzymes to break down various unwanted or outdated materials within the cell.
Line 4: Vacuoles: The vacuole is the membrane-bound space found in the cytoplasm.
Explanation: This line introduces vacuoles as another type of membrane-bound compartment within the cytoplasm. Unlike lysosomes, they are not primarily for digestion.
Line 5: It contains water, sap, excretory product and other materials not useful for the cell.
Explanation: This line describes the typical contents of a vacuole. It can store various materials, including: Water: Makes up a significant portion of the vacuole’s content. Sap: A watery solution containing dissolved substances like nutrients or waste products. Excretory products: Materials the cell no longer needs. Other materials: Can vary depending on the cell type. Enrichment: Vacuoles act like storage compartments for the cell, managing water balance, storing nutrients or waste products, and maintaining internal pressure.
Line 6: The vacuole is bound by a single membrane called tonoplast.
Explanation: This line introduces the vacuolar membrane, called the tonoplast, which separates the vacuole’s contents from the cytoplasm.
Line 7: In plant cells the vacuoles can occupy up to 90 per cent of the volume of the cell.
Explanation: This line highlights the significant size that vacuoles can reach in plant cells. They can take up a large portion of the cell’s volume. Enrichment: Large plant vacuoles help maintain cell structure, store nutrients and waste, and regulate water balance in the plant.
Line 8: In plants, the tonoplast facilitates the transport of a number of ions and other materials against concentration gradients into the vacuole, hence their concentration is significantly higher inside the vacuole than in the cytoplasm.
Explanation: This line describes a special function of the tonoplast in plant cells. It can actively transport ions and other solutes (dissolved materials) into the vacuole against their concentration gradient (moving from low to high concentration). Enrichment: This allows plants to concentrate certain materials within the vacuole, which can be beneficial for various functions.
Line 9: In Amoeba the contractile vacuole is important for excretion.
Explanation: This line introduces a specific type of vacuole found in Amoeba, a single-celled organism. The contractile vacuole helps with excretion by collecting excess water and waste products and periodically expelling them from the cell.
Line 10: In many cells, as in protists, food vacuoles are formed by engulfing the food particles.
Explanation: This line describes another type of vacuole, the food vacuole, found in some protists (single-celled eukaryotes) like Amoeba. These vacuoles form around ingested food particles for digestion. Enrichment: The breakdown of food particles within the food vacuole occurs with the help of digestive enzymes released into the vacuole.