The _________ regulates the flow of contents from the stomach to the duodenum.

A. Heme does not get converted into amino acids. Instead, heme is split into iron and a porphyrin ring. The iron is stored or reused, and the porphyrin ring is converted into biliverdin and then bilirubin for excretion. This pathway is completely different from protein hydrolysis.

B. Globin: The blue box leads to a pathway labeled “hydrolyzed to free amino acids.” This describes what happens to the globin portion of hemoglobin. Globin consists of protein chains, and when red blood cells are broken down, these protein chains are hydrolyzed into individual amino acids. The body then reuses these amino acids to build new proteins or for other metabolic functions. Therefore, box 2 represents globin.

C. Erythropoietin is not part of hemoglobin structure. It is a hormone that regulates red blood cell production. It is not broken down during

A. Pancreas: This gland regulates blood glucose levels by secreting the hormones insulin and glucagon from the islets of Langerhans. While it monitors glucose concentrations, it does not serve as a primary storage depot for glycogen. It facilitates glucose uptake in other tissues rather than sequestering it.

B. Stomach: The primary functions of this organ are mechanical churning and initial chemical proteolysis of the ingested bolus. It does not possess the metabolic pathways for glycogenesis or glycogenolysis. It serves as a temporary reservoir for food but not for systemic energy substrates.

C. Liver: Hepatocytes convert surplus blood glucose into glycogen through the process of glycogenesis for long-term storage. When blood sugar levels decline, the liver performs glycogenolysis to release glucose back into the systemic circulation. It acts as the central metabolic hub for glucose homeostasis.

D. Spleen: This lymphatic organ is primarily involved in filtering blood, recycling iron from senescent erythrocytes, and mounting immune responses. It serves as a reservoir for platelets and white blood cells rather than carbohydrates. It plays no significant role in the regulation of blood glucose levels.

E. small intestine: This is the principal site for the absorption of monosaccharides into the portal venous system following digestion. While it transports glucose across its epithelial lining, it does not store significant quantities of glycogen for systemic use. It functions as a gateway rather than a storage organ.