Question

If two type of molecules move together in opposite direction. Such type of transport is known as (a) Symport (b) Antiport (c) Uniport (d) All of these

Short answer

(b) Antiport

Step-by-step solution

Understanding the Types of Transport

There are three basic types of transports in a cell: Symport, Antiport, and Uniport. Symport is a type of active transport that moves two different molecules in the same direction; Uniport, as the name implies, involves the movement of one type of molecule; Antiport is a mechanism which transports two substances across a membrane in opposite directions.

Matching the Scenario to the Correct Type of Transport

The question describes a scenario in which two types of molecules move together in opposite direction. Comparing this scenario to the explanations provided in step 1, this matches the definition of ‘Antiport’ transport.

Select the Correct Answer

Given the comparison in step 2, the correct answer to this multiple choice question is 'Antiport'.

Key concepts

Symport

In cell transport mechanisms, 'symport' refers to the movement of two different molecules or ions in the same direction across a cell membrane. This process is a form of active transport that requires energy, often derived from ATP or the use of an electrochemical gradient.
Symport systems are essential for several cellular functions, including nutrient uptake and ion balance. For instance, the sodium-glucose symporter

• facilitates the absorption of glucose in the intestinal cells by simultaneously transporting sodium ions and glucose into the cell,
• relying on the gradient of sodium ions to pull glucose into the cell.

Understanding symport

• is crucial for grasping how cells manage substances essential for keeping the cell alive and energized.
• It highlights the interdependence of different molecules on the movement of others, like passengers on a bus sharing the same route.

Antiport

Antiport is a type of cell transport mechanism where two substances move simultaneously but in opposite directions across a cell membrane. This transport is often coupled with an energy process, allowing one substance to move against its concentration gradient while the other moves according to its gradient.
One classic example of an antiport mechanism is the sodium-potassium pump:

• It helps maintain the cell's electrochemical balance by pumping sodium ions out of the cell and potassium ions into the cell.
• This process is crucial for maintaining proper cell function, including nerve impulse transmission and muscle contraction.

Antiport systems

• demonstrate how cells can build and maintain gradients of ions, being essential for various cellular processes.
• They show how the energy derived from one molecule can be harnessed to move another molecule in the opposite direction.

Uniport

The concept of 'uniport' refers to the simplest form of transport mechanism within cells, characterized by the movement of a single type of molecule or ion across a membrane. This process can be either passive (requiring no energy) or active (requiring energy).

• In uniport, specific proteins facilitate the transport of molecules like ions, sugars, or amino acids across the membrane.
• For example, the glucose transporter GLUT1 is a uniport mechanism.

Glucose molecules are moved via facilitated diffusion,

• demonstrating how uniporters support vital cellular tasks such as maintaining energy balance and metabolic functions.
• These transport proteins allow the cell to adapt to external changes by altering the uptake rate of molecules precisely when they are needed.

Uniport highlights the straightforward efficiency of moving substances, critical in scenarios where only one molecule is involved in the transport process.