Chemicals & Human Health

Kidneys and Metals Problem Set

Problem 5: Types of metal toxicity

For help to answer the question:

One of the ways that lead makes people sick is by interfering with the protein that helps make hemoglobin. The result is an anemic like condition where your blood can't carry enough oxygen to keep you healthy. This is an example of what mechanism of metal toxicity?
A. enzyme inhibition
B. carcinogenicity
C. disruption of subcellular organelles
D. corrosion


Enzyme inhibition
Many metals exert their toxic effects by interfering with enzymatic reactions in the body cells. Enzymatic reactions in the body are chemical reactions that are facilitated by special proteins called enzymes. For example, the "heme" group from hemoglobin is manufactured by a complex series of enzymatic reactions. Five of the enzymes involved in heme synthesis do not work very well at all in the presence of lead; that is, they are "inhibited" by lead. This can lead to anemia, a reduction in the number of red blood cells.

synthesis of heme hemoglobin molecule with iron

Disruption of subcellular organelles
lead inclusion bodies in an xray of the gut Another type of damage often caused by metals occurs when they disrupt the function of organelles, such as the endoplasmic reticulum, lysozymes or mitochondria. This can happen when metals interfere with the enzymes in the organelle or sometimes by the presence of metal inclusion bodies. In the kidney tubules, mercury causes problems by interfering with the work of the cell membrane. Mercury binds to membrane proteins, disrupting their regular work of reabsorbtion of water and important solutes.

Some metals can cause cancer. Arsenic, for example, has been linked to lung cancer and skin cancer. Scientists are not sure yet how metals cause cancer, but it may be because some metals somehow interact with DNA.

Lastly, because metals can be in several different charge states, they become easily involved with oxidation and reduction reaction and this can lead to corrosion or oxidative damage.

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Kidneys and Metals Problem Set Chemicals and Human Health vocabulary the biology project

The Southwest Environmental Health Sciences Center
The Biology Project
The University of Arizona
Monday, February 22, 1999
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