Tuesday, November 25, 2008


I am again in my “correcting misconception” mood today. I encounter so many of them in several biology textbooks and I always feel shivers ran up and down my spine every time I see them. I know that textbooks are the major source of information for most of our teachers so I don’t understand how such books (full of misconceptions) can even be approved as text. I also don’t understand how some authors can write some out of this world information.

Today my topic is about plasmolysis. I was shocked to read this in one textbook - “Plasmolysis explains why your skin wrinkles” What?

Please, plasmolysis does not cause wrinkling of the skin!!!

Plasmolysis occurs in plant and bacterial cells, not in human cells. When plant cells are placed in extremely hypertonic environment, water moves out of the cells by osmosis. This causes the plant vacuoles to shrink and the cell membrane detaches from the cell wall. This is plasmolysis.

Animal cells do not have cell walls so there is no such thing as detachment of cell membrane if cells are exposed to hypertonic environment. So plasmolysis does not occur in animal cells.

Red blood cells shrink or undergo crenation if placed in hypertonic solution in laboratory condition. Under laboratory condition also, blood cells bloat and even burst if placed in hypotonic solution. However, in natural condition these do not happen because our body has a system for regulating water loss and gain such that our individual cells are protected from shrinking or bursting.

No comments:

Related Posts Plugin for WordPress, Blogger...