TEACHER ANSWER KEY
Answer the following questions about information from this unit.
1. Can you think of what would eventually happen
to the stomach if an ulcer were left untreated?
If a stomach ulcer was left untreated, it would eventually eat
through the lining of the stomach and cause internal
bleeding. This could also allow the stomach acids to
damage tissues outside of the stomach, causing serious
problems because of the low pH of the stomach fluids.
2. Can you think of how an antibiotic kills only bacteria but not the cells in your
body? What structural feature might be different in bacteria than in your cells?
As was discussed in the bodily defenses module, antibiotics only kill the bacteria and not the
cells in your body. The reason they are able to kill the bacteria is because the bacteria have
different proteins and enzymes on the surface of their membranes than do the cells in your body.
The chemicals in the antibiotics are able to penetrate the surface of the bacteria to kill them.
Whereas the membrane on the outside of our body cells prevents the antibiotics from harming
them.
3. Speculate on why the ulcer causing bacteria can survive
in your stomach, but not other types of bacteria. What
condition exists in the stomach that the ulcer-causing
bacteria would have to withstand?
Student responses may vary as long as they are supported, but the
real answer is that the bacteria can convert the substance called urea
to carbon dioxide (gas) and another substance called ammonia. The
bacterium, H. pylori, produces a very active form of the urea enzyme. The ammonia produced
from the urea neutralizes the acid (like adding baking soda to lemon juice) in the area where the
bacteria are growing, and allows the bacteria to become established and grow (an infection)
within the epithelial tissue. The bacteria has to withstand the stomach acid that is highly acidic
(low pH).
Digestive System: Activity 3
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