Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
The primary function of the digestive system is to break down large, insoluble food molecules into small, soluble molecules like glucose () that can be absorbed into the bloodstream.
Mechanical Digestion: The physical breakdown of food into smaller pieces, occurring in the mouth (teeth) and the stomach (churning). This increases the surface area for enzymes to act upon.
Chemical Digestion: The use of biological catalysts called enzymes to break chemical bonds. For example, Hydrochloric acid () in the stomach provides the optimum for protease enzymes.
The Alimentary Canal: The continuous tube through which food passes, including the mouth, esophagus, stomach, small intestine, and large intestine.
Absorption and Villi: Most absorption occurs in the small intestine. The walls are covered in tiny, finger-like projections called villi, which increase the surface area to maximize the intake of nutrients.
Egestion vs. Excretion: Egestion is the removal of undigested food waste from the anus, whereas excretion is the removal of metabolic waste produced by cells.
📐Formulae
💡Examples
Problem 1:
Explain why the stomach contains Hydrochloric acid () and what its effect is on enzymes like pepsin (a protease).
Solution:
The creates an acidic environment with a low .
Explanation:
The acid kills harmful bacteria ingested with food and provides the optimum (around 2) for protease enzymes to effectively break down protein chains into amino acids.
Problem 2:
A student tests a piece of bread (starch) with iodine solution. After chewing the bread for 5 minutes, they test it again. Describe the expected change using the enzyme Amylase as a reference.
Solution:
The iodine stays orange/brown instead of turning blue-black.
Explanation:
Saliva contains the enzyme Amylase. As the student chews, Amylase breaks down the long-chain starch molecules into simple sugars (). Since starch is no longer present, the iodine test for starch returns a negative result.
Problem 3:
Describe how the structure of a villus in the small intestine aids in the absorption of molecules like glucose ().
Solution:
Villi provide a large surface area and thin walls.
Explanation:
The finger-like shape increases the total surface area available for diffusion. The walls are only one cell thick, allowing a short diffusion distance for nutrients to enter the blood capillaries.