Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Absorption is defined as the movement of small food molecules and ions through the wall of the intestine into the blood.
The small intestine, specifically the ileum, is adapted for absorption by having a very large surface area created by villi and microvilli.
Each villus has a wall only one cell thick to minimize the diffusion distance for molecules like and amino acids.
Capillaries within the villi absorb water-soluble nutrients and transport them to the liver via the Hepatic Portal Vein.
Lacteals are specialized vessels in the villi that absorb fats (lipids), which are later transported into the lymphatic system.
Assimilation is the movement of digested food molecules into the cells of the body where they are used, becoming part of the cells.
In the liver, excess is converted into glycogen for storage under the influence of insulin.
Deamination occurs in the liver, where the nitrogen-containing part of amino acids is removed to form urea, .
📐Formulae
💡Examples
Problem 1:
Explain how the structure of a villus facilitates the absorption of glucose () and amino acids.
Solution:
Glucose and amino acids are absorbed via facilitated diffusion and active transport into the blood capillaries within the villus.
Explanation:
The villus is lined with a single layer of epithelium cells (one cell thick) which ensures a short diffusion path. The constant flow of blood in the capillaries maintains a steep concentration gradient (), ensuring that continues to move from the lumen of the small intestine into the plasma.
Problem 2:
A person consumes a high-protein meal. Describe the process of assimilation for the resulting amino acids.
Solution:
Amino acids are used to synthesize proteins such as enzymes, hormones, or muscle fibers like actin and myosin.
Explanation:
Once absorbed, amino acids travel to the liver. The body cells take up these amino acids to build new cytoplasm or proteins. Any excess amino acids cannot be stored and undergo deamination to form , which is excreted by the kidneys.