Cells of the pancreas make digestive enzymes, which are proteins, and send them out into the gut…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Cells of the pancreas make digestive enzymes, which are proteins, and send them out into the gut. A researcher follows a new enzyme molecule from the moment it is made. (a) On which kind of ER is it made? (b) At which face does it enter the Golgi stack, and at which face does it leave? (c) How does it reach the cell surface? (d) Name two kinds of molecule that the Golgi apparatus is an important site for forming.
Need a reminder? The key ideaShow
Endomembrane system: ER, Golgi complex, lysosomes and vacuoles, with coordinated functions; not mitochondria, chloroplasts or peroxisomes. Rough ER: ribosomes, protein synthesis and secretion. Smooth ER: lipids, and steroid hormones in animal cells. Golgi apparatus: stacked cisternae with a cis (forming, convex) face and a trans (maturing, concave) face; packaging; glycoproteins and glycolipids. Lysosomes: from the Golgi, hydrolases active at acidic pH. Vacuoles: bound by the tonoplast, up to 90 per cent of a plant cell; contractile vacuoles in Amoeba; food vacuoles in protists.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The ER. It is made on the rough ER, which carries ribosomes.
Step 2. The Golgi. Vesicles from the ER fuse with the cis face. The enzyme moves through the stack and leaves from the trans face.
Step 3. To the surface. It is packed into a secretory vesicle, which carries it to the cell membrane.
Step 4. Golgi products. Glycoproteins and glycolipids.
Answer: (a) rough ER; (b) in at the cis face, out at the trans face; (c) in a vesicle from the trans face; (d) glycoproteins and glycolipids.
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