Trace the path of a single protein molecule that has been ingested.
The protein molecule will be digested by enzymes made by
a. The mouth, stomach, and colon
b. The stomach, liver, and small intestine
c. The small intestine, mouth, and liver
d. The pancreas, stomach, and small intestine

Verified step by step guidance

1. Step 1: Understand the process of protein digestion, which involves breaking down proteins into smaller peptides and amino acids by specific enzymes produced in different organs.
2. Step 2: Identify the organs involved in protein digestion. The mouth primarily uses mechanical digestion and saliva, which contains amylase for carbohydrates but not enzymes for protein digestion.
3. Step 3: Recognize that the stomach produces pepsin, an enzyme that begins protein digestion by breaking proteins into smaller peptides.
4. Step 4: Know that the pancreas secretes proteolytic enzymes like trypsin and chymotrypsin into the small intestine, where most protein digestion occurs.
5. Step 5: Understand that the liver produces bile, which aids fat digestion but does not produce enzymes for protein digestion, and the colon mainly absorbs water and electrolytes, not involved in protein digestion.

Key Concepts

Protein Digestion Process

Protein digestion begins in the stomach where enzymes like pepsin break proteins into smaller peptides. This process continues in the small intestine with enzymes such as trypsin and chymotrypsin from the pancreas, further breaking peptides into amino acids for absorption.

Role of Digestive Organs and Enzymes

Different organs contribute specific enzymes for digestion: the stomach produces pepsin, the pancreas secretes proteases like trypsin, and the small intestine completes digestion and absorbs nutrients. The liver produces bile but does not secrete protein-digesting enzymes.

Pathway of Ingested Protein Molecule

An ingested protein molecule travels from the mouth (mechanical digestion), to the stomach (chemical digestion by pepsin), then to the small intestine where pancreatic enzymes finish digestion. The colon mainly absorbs water and does not digest proteins.