Final answer:
Insulin cannot be taken orally because it would be destroyed by stomach acids. It's usually administered through injections to bypass the digestive system, allowing it to help decrease blood glucose levels by promoting glucose uptake into cells and inhibiting liver glucose production. Disruption of insulin production by the immune system can cause diabetes, requiring exogenous insulin administration.
Step-by-step explanation:
Why Insulin Cannot Be Taken Orally
Insulin cannot be taken orally because option a is correct - it is destroyed by stomach acids. When ingested, the digestive enzymes and acids in the stomach break down insulin, which is a protein, preventing it from being absorbed intact into the bloodstream to exert its effect. Insulin injections circumvent this issue by directly introducing the hormone into the subcutaneous tissue, where it can be steadily absorbed into the bloodstream. These injections help to decrease blood glucose levels after consuming a meal, as insulin facilitates the transport and storage of glucose in tissues, particularly in muscle and fat cells. Furthermore, insulin helps in the regulation of blood glucose levels by inhibiting the production of glucose by the liver.
The relevance of insulin's role can also be seen in pathological conditions such as diabetes. For instance, in type 1 diabetes, the immune system mistakenly attacks and destroys the beta cells of the pancreas, leading to insufficient insulin production. In such cases, the absence of functional insulin impedes negative feedback mechanisms that normally lower high blood sugar levels, necessitating the administration of exogenous insulin.