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:
Hypoxia causes parts of your body to become deprived of oxygen and can result in severe damage to those areas. When retinas are deprived of oxygen they become damaged, which can lead to various eye diseases and conditions such as diabetic retinopathy, macular degeneration, and glaucoma.