Describe the role of villi and lacteals in nutrient absorption and how to test for glucose.

Here are the answers to your questions:

a)
A: Lacteal
B: Blood capillaries

b)
Villi are found in the small intestine.

c)
One carbohydrate carried in B (blood capillaries) is glucose.

d)
To test for glucose (a reducing sugar), you can perform the Benedict's test.

• Safety Rule: Wear safety goggles to protect your eyes from chemical splashes. Handle hot apparatus with care.

• Materials and Reagents:

  • Test tube
  • Test tube rack
  • Beaker (for water bath)
  • Bunsen burner or hot plate
  • Dropper or pipette
  • Sample solution (e.g., the substance to be tested for glucose)
  • Benedict's solution (blue)

• Procedure:

  1. Add approximately $2\,\text{cm}^3$ of the sample solution into a clean test tube.
  2. Add an equal volume (about $2\,\text{cm}^3$) of Benedict's solution to the test tube.
  3. Place the test tube in a hot water bath (heated to about $80-100^\circ\text{C}$) for $5-10$ minutes.
  4. Observe any color change in the solution.

• Conclusion:

  • If the solution changes color from blue to green, yellow, orange, or a brick-red precipitate forms, then reducing sugars (like glucose) are present.
  • If the solution remains blue, then no reducing sugars are present.

• Deduction:

  • The formation of a brick-red precipitate indicates a high concentration of reducing sugar.
  • A green or yellow color indicates a low concentration of reducing sugar.
  • The Benedict's test specifically detects reducing sugars, which include monosaccharides (like glucose) and some disaccharides.