Problem 124 - Objective Biology for NEET

Question

Glucose and amino acids are absorbed in the intestine by (a) Active transport (b) Passive transport (c) Selective absorption (d) Osmosis

Step-by-Step Solution

Answer

The absorption of glucose and amino acids in the intestine mainly occurs through active transport.

Step 1: Eliminate incorrect options

First, eliminate osmosis as a possible answer because osmosis is mainly related with the movement of water molecules, which is not the case for absorption of glucose and amino acids.

Step 2: Continue eliminating

Next, eliminate passive transport because the absorption of glucose and amino acids occurs against the concentration gradient, meaning it requires energy, which is not a characteristic of passive transport. Therefore passive transport is not how glucose and amino acids are absorbed.

Step 3: Final choice

Between active transport and selective absorption, it’s important to know that while selective absorption might occur to some extent, it is the active transport that plays a vital role. Energy is required for the absorption of these nutrients against the concentration gradient, which is a key feature of active transport. Therefore, the right answer is active transport.

Key Concepts

Active Transport

In the intestines, absorbing nutrients like glucose and amino acids often requires energy, which is why active transport is essential. Unlike other methods, active transport moves substances against their concentration gradient. This means that molecules move from areas of lower concentration to higher concentration. This process requires energy in the form of ATP (adenosine triphosphate).

There are several important features of active transport:

• Energy Dependency: Requires energy to occur.
• Specificity: Only particular molecules or ions are transported.
• Protein Involvement: Transport proteins in the cell membrane aid in the process.

This active transport mechanism ensures that the cells get the necessary nutrients, even when they are in lower concentrations in the intestine.

Passive Transport

Passive transport is a type of natural diffusion. Unlike active transport, it does not require energy. It relies on the concentration gradient, moving molecules from areas of high concentration to areas of low concentration, naturally passing through the cell membranes by itself.

Key aspects of passive transport include:

• No Energy Required: Utilizes the natural kinetic energy of particles.
• Moves Down The Gradient: Unlike active transport, passively moves substances from higher to lower concentrations.
• Includes forms like diffusion and facilitated diffusion.

Even though passive transport is efficient, it isn't suitable for absorbing glucose and amino acids in the intestine, as they often need to move against their concentration gradients.

Osmosis

Osmosis is a specialized form of passive transport, specifically for water molecules. It involves the movement of water across a semipermeable membrane, from an area of low solute concentration to an area of high solute concentration. The goal is to balance solute concentrations on both sides of the membrane through water movement.

Here are some quick points about osmosis:

• Water Movement: Only affects water molecules.
• Facilitating Concentration Balance: Moves water to equalize solute concentrations.
• Passive Process: Does not require external energy input.

Although osmosis is crucial for maintaining cellular water balance, it does not play a direct role in absorbing glucose and amino acids.

Selective Absorption

Selective absorption refers to the ability of the intestine to choose which molecules are absorbed and which are not. This process ensures that nutrients necessary for the body are absorbed preferentially. Although selective absorption happens to some degree in our intestines, it typically supports rather than drives the primary nutrient absorption processes.

Characteristics of selective absorption include:

• Specific Uptake: Prioritizes certain nutrients.
• Regulated: Often involves certain checks or balance mechanisms to ensure appropriate absorption.

While selective absorption is important, active transport remains the primary mechanism for absorbing glucose and amino acids. It helps ensure that vital nutrients are transported effectively to where they are needed most.