Summary and Exam Tips for Digestion and Absorption
Digestion and Absorption is a subtopic of Human Physiology, which falls under the subject Biology in the IB DP curriculum. The oesophagus is a hollow tube that connects the oral cavity to the stomach, facilitating the movement of food via peristalsis. The stomach acts as a temporary storage tank where food is mixed and protein digestion begins in an acidic environment. The small intestine is a long, folded tube where nutrients are absorbed, consisting of the duodenum, jejunum, and ileum. The large intestine absorbs water and minerals, comprising sections like the ascending, transverse, descending, and sigmoidal colon, and the rectum.
Salivary glands release enzymes like amylase to initiate starch breakdown. The pancreas produces enzymes and hormones like insulin and glucagon, while the liver processes absorbed materials, producing bile stored in the gallbladder. Peristalsis in the small intestine ensures thorough mixing with enzymes. Pancreatic juice contains enzymes for digesting macromolecules, and the small intestine is where final digestion occurs. Villi in the small intestine increase surface area for absorption, absorbing monomers, ions, and vitamins. Membrane transport methods are crucial for nutrient absorption, and glucose is co-transported with sodium ions into epithelial cells, then diffused into blood plasma.
Exam Tips
- Understand Key Processes: Focus on how peristalsis, enzyme action, and nutrient absorption occur in the digestive system.
- Memorize Enzyme Functions: Know which enzymes break down specific macromolecules, such as amylase for starch and lipase for triglycerides.
- Diagram Practice: Be able to draw and label the digestive system, noting key structures like the stomach, liver, and intestines.
- Villi Functionality: Remember how villi increase surface area for absorption and the types of nutrients absorbed.
- Transport Mechanisms: Familiarize yourself with different membrane transport methods used in nutrient absorption, such as co-transport and facilitated diffusion.
