Gastric enzyme which is present in the stomach of infants but absent from stomach of adults
**Core Concept**
The question is testing the knowledge of gastric enzymes present in the stomach, specifically in infants and adults. Gastric enzymes play a crucial role in protein digestion, and their presence or absence can affect the digestive process.
**Why the Correct Answer is Right**
In infants, the gastric enzyme pepsinogen is present in the stomach in the form of pepsinogen C, which is activated to pepsin by gastric acidity. Pepsin is responsible for breaking down proteins into smaller peptides. However, in adults, the predominant form of pepsinogen is pepsinogen A, which is activated to pepsin by gastric acidity. The presence of pepsinogen C in infants is thought to be due to the fact that infants have a higher pH in their stomachs, which allows pepsinogen C to remain active. As infants mature, the pH in their stomachs decreases, and pepsinogen A becomes the predominant form.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify a gastric enzyme present in infants but absent in adults.
**Option B:** This option is incorrect because gastric amylase is not a gastric enzyme present in infants, but rather a salivary enzyme.
**Option C:** This option is incorrect because gastric lipase is present in adults, but not specifically in infants.
**Option D:** This option is incorrect because gastric mucin is a protective substance in the stomach, not a gastric enzyme.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the presence or absence of gastric enzymes can affect the digestive process, particularly in infants and adults with certain medical conditions. For example, individuals with peptic ulcer disease may have an imbalance of gastric enzymes, leading to decreased protein digestion and increased risk of complications.
**Correct Answer: A. Pepsinogen C**