Science & Technology in Action

2nd Edition

The Kidney and What it Does.


This lesson deals with the kidney, what is does, how it functions and why it is essential for human life. The process of dialysis in the event of kidney failure is explained.
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Lesson excerpt


Our genes are the specific instructions carried by the DNA in each of our 1013 tissue cells. Being direct descendents of an original fertilised egg, our cells are genetically identical. All our body cells (somatic cells) have an identical collection of around 33,000 genes. 

What makes us different?
Each person has almost 300 different types of tissue cell. How is it that these tissue cells are different in structure if they are genetically identical? Each type of cell uses a different subset of our 33,000 genes. Brain cells use about 11,000 genes—far more than the 3000 used by the average human cell. Some genes are used by all our cells for the everyday operation and maintenance, such as aerobic respiration. A gene carries the information for the formation of a particular protein. Proteins have a wide variety of functions. Many of them are enzymes—molecules that catalyse biochemical reactions within the cell. Someare structural elements in cell membranes, tendons, ligaments, hair, etc. Others are involved in the transport of fats, vitamins, metals and hormones in the blood or act as receptors, antivirals or antibodies.

Genes and health
Our health depends on the body’s ability to make the required proteins correctly, at the right time and in the right quantity. Failure on just one of the many thousands of proteins can cause very serious medical problems. A faulty gene is the usual reason for the specific protein failure. In many cases the only possible remedy is gene therapy, in which the faulty gene is replaced with the correct version, or the missing protein is administered to the patient.

When can gene therapy be used?
Gene therapy is a difficult and complex process which is currently in an early stage of development and is used in the treatment of a limited number of medical conditions. Protein therapy has been successful for many medical problems such as Pompe disease.

True or False?

  1. The kinetic theory of matter is often called the particle theory. true
  2. Solids and liquids are fluids. false
  3. Diffusion is an active process. false
  4. Osmosis is a particular example of diffusion. true
  5. Only special cells in our kidneys carry out active transport. true
  6. Homeostasis is keeping our internal environment constant or stable. true
  7. Getting rid of undigested food from the gut is called excretion. false
  8. Filtration and selective reabsorption are means by which the kidneys excrete. true
  9. Filtration occurs at the glomerular blood capillaries. true
  10. Excreted materials are those deselected for reabsorption. false
  11. Kidney failure leads to pollution of our internal environment. true
  12. Dialysis is a method of treatment for kidney failure. true