Lock and Key Model. Each type of enzyme has a unique 3-D shape, including a surface groove called an active site, which fits its target substrate much like a key fits in a lock. Other substances that donât fit can't enter the active site and no reaction occurs.
Some of the many causes of hypoxia are the following: 1  Chemical or gas poisoning (for example cyanide, carbon monoxide) 2  Low or absent concentration of oxygen (for example, high altitudes reached without supplemental oxygen as seen in mountain climbing, and aviation, drowning or fires)  Lung problems, for example:
Cerebral hypoxia, induced through other forms of hypoxia, can cause brain damage, including brain cell death and other forms of mental deterioration. Studies have shown that abnormally low oxygen levels in the brain (cerebral hypoxia) have a clear association with the onset of Alzheimer's disease.hether it's from some form of blockage or through chronic exposure to an environment without adequate oxygen, oxygen deprivation in the brain can lead to some forms of dementia, including Alzheimer's Disease.