Chapter 20, Problem 1E

Summary Introduction

Introduction

Sodium helps to maintain the blood pressure of the body. It is also used by the nervous system for conduction of electrical signals from one part of the body to another. Fatty acids are one of the major sources of energy in the body and a key component of plasma layer of the cells. Vitamin A is essential for the healthy teeth and good vision.

Answer to Problem 1E

Correct answer

The correct answer is option (c).

Explanation of Solution

Explanation for the correct answer

Option (c) is given as they are transported into capillaries in the villi. The food is digested into simpler nutrients in the digestive system. Sodium, fatty acids and vitamin A are absorbed in the small intestine. The walls of small intestine contain hair like outgrowths called villi that increase the surface area to facilitate absorption of these nutrients. Hence, the correct answer is option (c).

Explanation for the incorrect options

Option (a) is given as they are not enzymatically modified prior to their absorption into the blood stream. Vitamin A does not undergo any transformation before absorption. Hence, option (a) is incorrect.

Option (b) is given as they cross the apical membrane of enterocytes by simple diffusion. The transport of sodium requires sodium/potassium ion channels and special membrane proteins or channels are required for the active transport of vitamin A. Hence, option (b) is incorrect.

Option (d) is given as they are all hydrophilic. Fatty acids do no interact with water and are therefore, hydrophobic. Same is true for vitamin A. It is fat soluble and does not interact with water. Hence, option (d) is incorrect.

Option (e) is given as All the above. Since, options (a), (b) and (d) are incorrect, option (e) is also wrong.

Conclusion

Fatty acids, vitamin A and sodium are absorbed in the small intestine through hair like outgrowths known as villi, which increases the surface area of the intestine for the sole purpose of absorption.