Four situations are given. Name the junction that matters in each…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Four situations are given. Name the junction that matters in each.
- Digested food in the intestine must not leak between the cells into the body.
- Skin cells must stay together when the skin is stretched.
- A signal to contract must pass from one heart muscle cell to the next, so that the cells contract as a unit.
- A drug blocks the channels between the heart cells. What is the likely effect on the heart?
Need a reminder? The key ideaShow
Cell junctions join the cells of a tissue. Tight junctions stop substances from leaking between cells. Adhering junctions cement neighbouring cells together. Gap junctions join the cytoplasm of adjoining cells so that ions and small molecules pass quickly. A gland is made of cells that secrete. A goblet cell is a unicellular gland, and the salivary gland is multicellular. Exocrine glands send their products through ducts. Endocrine glands have no duct and release hormones into the fluid around them.
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. (a) A tight junction. It stops substances from leaking across the tissue.
Step 2. (b) An adhering junction. It cements neighbouring cells together.
Step 3. (c) A gap junction. It joins the cytoplasm of the cells so that ions and small molecules pass quickly.
Step 4. (d) The channels are gap junctions, so the signal would not pass quickly from cell to cell. The cells would not contract as a unit, and the heart would pump badly. This is an inference from the function of the junction.
Answer: (a) tight; (b) adhering; (c) gap; (d) the cells would not contract together.
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