Question

Water, mineral and food are generally moved by over large distance by (a) Simple diffusion (b) Facilitated diffusion (c) Active transport (d) Bulk flow or mass flow

Short answer

The correct answer is (d) Bulk flow or mass flow.

Step-by-step solution

Understanding the Concept

First, it's necessary to know what each term means. Simple diffusion is a process of spread of particles from a region of higher concentration to a region of lower without aid of any external factors. Facilitated diffusion, also from higher to lower concentration, involves carrier proteins to facilitate the movement. Active transport, uses energy to move substances from a region of lower to higher concentration. Bulk flow, or mass flow, is the movement of water and solutes together due to pressure.

Applying Knowledge to Solve

Now, thinking about the movement of water, minerals, and food over large distances, we need to consider the method that involves the movement of large quantities due to the pressure difference. Among these options, simple diffusion, facilitated diffusion and active transport are generally effective at short distances because they operate at the cellular level. For large distances, Bulk flow or Mass flow involves movement of large molecules like water, minerals, and food due to the pressure difference, making it the most suitable answer.

Key concepts

Simple Diffusion

Simple diffusion is a fundamental process in which particles move from an area of higher concentration to an area of lower concentration. It operates without the aid of energy or external factors, relying solely on the natural kinetic energy of the molecules. This movement occurs until there is an equilibrium in concentration across the space.
In biological systems, simple diffusion is crucial for the transfer of small, nonpolar molecules such as oxygen and carbon dioxide across cell membranes.
Unlike some other transport processes, it does not require any special proteins or structures, making it a straightforward and essential mechanism for cellular function.

Key characteristics of simple diffusion include:

• No energy requirement (passive process)
• Molecules move down their concentration gradient
• Effective over short distances

Understanding simple diffusion helps us appreciate how cells maintain balance and enable efficient molecular exchange.

Facilitated Diffusion

Facilitated diffusion is similar to simple diffusion in that it involves the movement of substances from an area of higher concentration to one of lower concentration. However, facilitated diffusion is distinct because it requires the help of specific carrier proteins embedded in the cell membrane.
These proteins provide a pathway that allows larger or polar molecules, such as glucose or ions, to cross the membrane more easily.
The process is still passive, meaning it does not require the input of energy from ATP.

Highlights of facilitated diffusion:

• Uses carrier proteins or channels
• Enables the transport of larger or charged molecules
• Passive process with no energy input required

By facilitating the transport of essential molecules, this diffusion mechanism underlines the importance of membrane proteins in maintaining cellular function.

Active Transport

Active transport is a crucial cellular process that moves molecules or ions from a region of lower concentration to a region of higher concentration. Unlike diffusion, active transport requires energy, usually in the form of ATP, to drive this movement against the concentration gradient.

This is often achieved through specific transport proteins found in the cellular membrane, known as pumps. A common example is the sodium-potassium pump, which maintains essential gradients of sodium and potassium ions across the cell membrane.

Key elements of active transport:

• Energy-dependent process (requires ATP)
• Molecules move against their concentration gradient
• Involves specific carrier proteins

Active transport is vital for various physiological functions, including nutrient uptake, waste removal, and maintaining cellular homeostasis. Without this energy-driven process, cells would not be able to maintain the necessary balances of key molecules and ions.