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 differs from hypoxemia in that hypoxia refers to a state in which oxygen supply is insufficient, whereas hypoxemia refers specifically to states that have low arterial oxygen supply. Hypoxia in which there is complete deprivation of oxygen supply is referred to as anoxia.actic acid build up (in tissues and blood) is a sign of inadequate mitochondrial oxygenation, which may be due to hypoxemia, poor blood flow (e.g., shock) or a combination of both. If severe or prolonged it could lead to cell death. In humans, hypoxia is detected by chemoreceptors in the carotid body.