NEET
Real Golgi region from a cell, reconstructed from electron tomography (a thin slice; colours = membranes segmented by the original authors). Look for stacks of thin, flat, parallel sheets and many small round vesicles: the same features as in the tour. The authors’ part names do not say which side is cis or trans, so no cis/trans labels are added here. The grey tags are the authors’ own file names for each part (for example ER_); SciSim has not re-identified the parts.
Real Golgi data: “Golgi Apparatus from EM Tomography”, NIH 3D 3DPX-000003, public domain (CC0 1.0). Electron tomography data (cryo-fixed, sectioned specimen): Rachid Sougrat; segmentation: Edwin Funge; colourised by Jeremy Swan (NIH). Related Cell Image Library entry (the 2008 “Golgi Apparatus” animation by the same team): CIL:7199 (doi:10.7295/W9CIL7199). 3D-print base removed and simplified for the web by SciSim. The animated cell, Golgi, vesicles and molecules are built in code by SciSim and drawn far larger than true scale. Narration uses your browser’s built-in voice.
How do vesicles find the right place? Small coated vesicles carry cargo between compartments. COPII-coated vesicles carry cargo forward from the ER to the Golgi. COPI-coated vesicles carry escaped ER proteins back to the ER (retrograde transport) and move material between cisternae. Clathrin-coated vesicles leave the trans-Golgi network, for example with lysosomal enzymes.
How does cargo cross the stack? Scientists still study this. In the cisternal maturation model, each cisterna itself slowly changes from cis to trans while its enzymes are recycled backwards; small vesicles also carry some cargo between cisternae. The tour shows cargo at different stages in each cisterna without choosing a model.
Lysosome address tag. Enzymes for lysosomes get a phosphate tag on a sugar (mannose-6-phosphate) in the cis Golgi; receptors in the trans-Golgi network recognise it and pack these enzymes into vesicles bound for lysosomes.
Cutting proteins. Some proteins are made as longer, inactive forms and cut into the active hormone or enzyme. For example, proinsulin is cut to insulin; this starts in the trans-Golgi network and finishes in the secretory vesicles.
Two kinds of secretion. Some vesicles fuse with the plasma membrane all the time (constitutive secretion); others are stored and fuse only when the cell gets a signal (regulated secretion, e.g. insulin release from pancreas cells).
Pick one answer for each question, then press Check my answers to see the explanations.
A 15–20 minute Class 11 lesson on the Golgi apparatus (NCERT Ch. 8, endomembrane system). (1) Project the guided tour with Narrate on; pause after scenes 3, 5 and 6 and ask: which face receives? which face ships? where does this vesicle go? (2) In Explore, students tap the cis face, trans face, a secretory vesicle and a lysosome and say each one’s job. (3) Open Real Golgi (EM data) and ask what looks the same as the model (flat stacked sheets, vesicles) and what looks different (real cisternae are uneven, curved and full of holes). (4) Finish with the 10-question check. Remind students that the animation is not to scale: a real cisterna is about 0.5–1 µm across, a transport vesicle only about 60–90 nm, and proteins are far smaller still.
The Golgi apparatus (Golgi body, Golgi complex) is a stack of flat, membrane-bound sacs called cisternae, found in eukaryotic cells. It receives proteins and lipids made in the endoplasmic reticulum, modifies them (for example by adding and trimming sugar groups), sorts them, packages them into vesicles and sends them to the plasma membrane, to lysosomes or to other places in the cell. It is an important site for making glycoproteins and glycolipids.
Key takeaway: the Golgi modifies, sorts, packages and ships proteins and lipids.The cis face (forming face) is the convex side of the stack that faces the ER and nucleus; vesicles from the ER fuse with it, so it is the receiving side. The trans face (maturing face) is the concave side that faces the plasma membrane; vesicles bud off from it, so it is the shipping side. The two faces are different but interconnected, and materials move from the cis face toward the trans face.
Key takeaway: cis = forming, convex, receives; trans = maturing, concave, dispatches.Lysosomal enzymes are made on the rough ER and travel to the Golgi. There they receive a special sugar-phosphate tag (mannose-6-phosphate). At the trans face the tagged enzymes are packed into vesicles that carry them to lysosomes. This is why NCERT says lysosomes are formed by packaging in the Golgi apparatus.
Key takeaway: the Golgi tags and packs lysosomal enzymes.In plant cells the Golgi apparatus usually exists as many small, separate stacks scattered through the cytoplasm. These stacks are often called dictyosomes. They make polysaccharides such as pectin and hemicellulose for the cell wall (cellulose itself is made at the plasma membrane) and supply the vesicles that form the cell plate when a plant cell divides.
Key takeaway: dictyosomes = Golgi stacks of plant cells.The Golgi is large and active in secretory cells that export a lot of protein, such as pancreas cells (digestive enzymes, insulin) and the mucus-secreting goblet cells of the intestine. Prokaryotic cells (bacteria) have no Golgi, because they have no membrane-bound organelles, and mature red blood cells of mammals have lost their Golgi along with their nucleus.
Key takeaway: secretory cells have a big Golgi; prokaryotes and mature mammalian RBCs have none.The Italian scientist Camillo Golgi first described it in 1898. Using a silver-staining method on nerve cells, he saw a densely stained net-like structure near the nucleus, which he called the internal reticular apparatus. It was later named after him. Its stacked-sac structure was seen clearly only with the electron microscope.
Key takeaway: Camillo Golgi, 1898.