Question

The products of digestion are a. large macromolecules needed by the body. b. enzymes needed to digest food. c. small nutrient molecules that can be absorbed. d. regulatory hormones of various kinds. e. the food we eat.

Short answer

The correct answer is (c) small nutrient molecules that can be absorbed. Digestion breaks down large macromolecules into smaller, more manageable nutrient molecules that our body can absorb and use.

Step-by-step solution

Understand the Concept of Digestion

Digestion is the process by which food is broken down into smaller components that can be easily absorbed by the body. This process involves mechanical and chemical processes, with the help of enzymes. The main purpose of digestion is to break down large macromolecules into smaller, more manageable nutrient molecules that our body can use.

Analyze Each Option

Now, let's analyze each option one by one to find the correct answer: a. large macromolecules needed by the body: This is not correct because digestion breaks down macromolecules, it does not produce them. b. enzymes needed to digest food: Enzymes are essential during digestion, but they help in the process and are not the final product of digestion. c. small nutrient molecules that can be absorbed: This could be correct, as the main goal of digestion is to break down the food into smaller molecules that can be absorbed and used by the body. d. regulatory hormones of various kinds: This is incorrect; although some hormones help regulate the digestive process, they are not the products of digestion. e. the food we eat: This is incorrect because the food we eat is what our body starts with, not the end result after digestion.

Choose the Correct Answer

After analyzing each option, the correct answer is c. small nutrient molecules that can be absorbed. These small molecules are the products of digestion and can be absorbed into the bloodstream to provide the body with essential nutrients it needs for proper functioning.

Key concepts

Nutrient Absorption

Nutrient absorption is a critical step in the digestive process, where the small nutrient molecules, broken down from larger food particles, are absorbed into the bloodstream. This primarily occurs in the small intestine, which is specially equipped for this task.

The interior of the small intestine has tiny, finger-like projections called villi and even smaller microvilli, which greatly increase the surface area for absorption. This means more nutrients can be absorbed efficiently.

• Villi contain blood vessels and lymph vessels, allowing absorbed nutrients to directly enter the body’s circulation.
• Amino acids and simple sugars go into the bloodstream, while fatty acids and glycerol usually enter the lymphatic system.

By absorbing these small molecules, the body obtains the necessary building blocks and energy to function properly.

Digestive Enzymes

Digestive enzymes play a vital role in breaking down food into absorbable nutrients. They are proteins that catalyze chemical reactions and are specific to different types of food molecules. Without enzymes, our body would struggle to process food efficiently.

Different enzymes target specific macromolecules:

• Amylase: Found in saliva and the pancreas, it breaks down carbohydrates into simple sugars.
• Proteases: These break proteins into amino acids, and are produced in the stomach and pancreas.
• Lipases: Produced by the pancreas, they break down lipids (fats) into fatty acids and glycerol.

Each enzyme operates at specific pH levels and temperatures, optimized to their particular location in the digestive tract.

Macromolecule Breakdown

Macromolecules, such as carbohydrates, proteins, and fats, form the bulk of our food. The breakdown of these large molecules into smaller components is essential for absorption and use by the body.

During digestion, each type of macromolecule undergoes specific processes:

• Carbohydrates: Broken down to simple sugars like glucose by amylase and other enzymes.
• Proteins: Digested into amino acids by proteases.
• Fats: Lipases transform fats into fatty acids and glycerol. Bile from the liver also helps to emulsify fats, making them easier to break down.

These smaller molecules can pass through the intestinal wall and be used by the body to build, repair, and fuel cells.

Mechanical and Chemical Digestion

The digestive process involves both mechanical and chemical digestion, working together seamlessly to break down food. Mechanical digestion starts in the mouth with chewing, which physically reduces food size and makes it easier to swallow.

Further mechanical processes occur in the stomach, where food is churned to mix with digestive juices.

• Chewing: Increases the surface area of food for enzymes to work on.
• Stomach churning: Mixes food with acid and enzymes, enhancing chemical digestion.

Chemical digestion, primarily powered by digestive enzymes, breaks down complex molecules into simpler forms. This begins in the mouth with salivary amylase and continues through the stomach and intestines. The combination of mechanical and chemical actions ensures that nutrients are efficiently broken down and ready for absorption.