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:
When a patient has hypoxia, some area of their body doesn't get enough oxygen. One of the symptoms of hypoxia is discolored skin, which can appear either bluish or bright red. There are many causes of hypoxia, which can affect either the entire body or just specific organs. Premature babies frequently suffer from hypoxia because their lungs are underdeveloped, and both mountain climbers and scuba divers are also at risk of developing hypoxia.