Problem 123 - Objective Biology for NEET

Question

Absorption of digested food is carried out by (a) Passive method (b) Active transport (c) Facilitated transport (d) All of these

Step-by-Step Solution

Answer

The correct answer is (d) All of these

Step 1: Understanding Transport Methods

First, one needs to know what each transport method means: \n - Passive transport is the movement of substances across the cell membrane without the use of energy by the cell. \n - Active transport is the energy-dependent movement of a substance across a biological membrane against a concentration gradient.\n - Facilitated transport, also known as facilitated diffusion, is a process by which substances are transported across cell membranes by means of protein carrier molecules.

Step 2: Applying the knowledge to Digestion

When digesting food, the body uses all of these methods. Small, non-polar molecules can move down the concentration gradient without the aid of transport proteins, which is a form of passive transport. Glucose and certain other substances are too large to diffuse directly and are assisted across the membrane by transport proteins, a process called facilitated transport. Some nutrients, cannot move by diffusion, so they're pumped across the membrane by active transport.

Step 3: Selecting the Answer

Given this understanding, it can be determined that the absorption of digested food isn't carried out by just one of these methods, but rather, all of these methods are employed. So the correct answer is (d) All of these.

Key Concepts

Passive Transport

Passive transport is a simple yet essential method of moving molecules across cell membranes. It functions without any input of energy from the cell. This process happens naturally and relies on the concentration gradient. Different types of passive transport include:

• Diffusion: Movement of small or non-polar molecules from an area of high concentration to low concentration.
• Osmosis: The diffusion of water molecules through a semi-permeable membrane.

During digestion, examples of passive transport include the absorption of some vitamins and small molecules, like water, that move effortlessly across the membrane.

Active Transport

Active transport is all about moving molecules against their concentration gradient, which is from an area of lower concentration to one of higher concentration. This process requires the cell to expend energy, often in the form of ATP, because it is working against the natural flow of diffusion. Examples of active transport in digestion:

• Sodium-potassium pump: Helps maintain cellular function and supports nutrient absorption.
• Glucose absorption: Cells in the intestine use active transport to absorb glucose, especially when concentrations are higher inside cells than in the gut.

This method ensures vital nutrients that can't diffuse passively are absorbed efficiently.

Facilitated Transport

Facilitated transport, or facilitated diffusion, is used when molecules cannot directly pass through the cell membrane due to their size or polarity. Instead, they need assistance from transport proteins that act as a passageway. In the context of digestion:

• Glucose and amino acids: These molecules are helped across the intestinal lining by specific transporter proteins.
• Ion channels: Allow ions to pass through the membrane while maintaining necessary cellular functions.

Facilitated transport ensures that essential molecules that are too large or charged can still be absorbed into cells, contributing to proper cellular function and digestion efficiency.

Digestion Process

The digestion process is a complex series of actions that break down food into absorbable molecules. Each type of transport plays a crucial role in assimilating the nutrients needed for bodily functions. Steps involved in digestion:

• Mechanical digestion: Physical breakdown of food into smaller parts, starting in the mouth.
• Chemical digestion: Enzymatic actions convert large molecules into smaller ones.
• Absorption: This is where various transport methods come into play to take nutrients, like glucose, fats, and proteins, from the digestive tract into the bloodstream.
• Excretion: Removal of waste products from the body.

Through these processes, the body harnesses energy and nutrients crucial for survival, demonstrating the essential role of each transport method in nutrition and health.