Problem 13 - Biology Concepts and Applications

Question

A transport protein requires ATP to pump sodium ions across a membrane. This is a case of ______ . a. passive transport b. active transport c. osmosis d. facilitated diffusion

Step-by-Step Solution

Answer

The correct answer is b. active transport.

Step 1: Understanding the Scenario

We need to identify the type of transport mechanism at play based on the requirement of ATP. The exercise mentions a protein using ATP to pump sodium ions, a clue to the mechanism type.

Step 2: Identifying the Role of ATP

ATP (adenosine triphosphate) is a molecule that provides energy for cellular processes. Its involvement suggests that energy is needed to carry out the transport process, hinting toward a specific type of transport.

Step 3: Distinguishing Transport Types

There are two main types of transport: passive and active. Passive transport does not require energy and includes processes like osmosis and facilitated diffusion. Active transport, on the other hand, requires energy from ATP to move substances against their concentration gradient.

Step 4: Matching the Description

The scenario describes sodium ions being pumped across a membrane with the use of ATP. Since ATP is explicitly mentioned, the process fits the characteristics of active transport, where energy is needed to move substances against their concentration gradient.

Key Concepts

ATP

ATP, or adenosine triphosphate, is often called the "energy currency" of the cell. It is the primary molecule cells use to store and transfer energy for various functions. When a cell performs tasks requiring energy, such as muscle contraction or, in this case, pumping ions across a membrane, ATP is utilized.

• ATP consists of three phosphate groups, attached to a ribose sugar and an adenine base.
• The bonds between the phosphate groups are high in energy, especially the bond between the second and third phosphate groups.
• When this bond is broken, energy is released and ATP is converted to ADP (adenosine diphosphate) plus an inorganic phosphate.

This released energy is what cells harness to perform work, including the active transport of sodium ions through transport proteins in cell membranes.

Sodium Ions

Sodium ions (Na⁺) play a crucial role in cellular processes and maintaining homeostasis. They are positively charged ions that must be carefully regulated within living organisms.

• Sodium ions are vital for nerve impulse transmission, muscle contraction, and various cellular functions.
• They tend to diffuse naturally from areas of high concentration to low concentration.
• In cells, sodium ions often need to be moved against their concentration gradient, from low to high concentration.

This movement against the gradient is achieved through active transport, usually requiring the energy supplied by ATP, enabling cells to maintain essential electrochemical gradients.

Transport Protein

Transport proteins are specialized proteins that span across the cell membrane, facilitating the movement of substances. There are specific transport proteins dedicated to the active transport of sodium ions across the membrane.

• These proteins are highly selective, only allowing certain ions or molecules to pass through.
• In active transport, these proteins change shape to move sodium ions from one side of the membrane to the other.
• The energy released from ATP breaking down into ADP is used to change the protein's shape, enabling it to carry substances across the membrane.

Transport proteins that use ATP to move substances, like sodium ions, across membranes against their concentration gradient, are indispensable in the function of both nerve cells and muscle cells.

Membrane

The cell membrane is a critical component responsible for maintaining the internal environment of the cell. Often called the "plasma membrane," it is semi-permeable, allowing selective entrance and exit of molecules.

• The membrane is primarily composed of a phospholipid bilayer, which provides a flexible and hydrophobic barrier.
• Embedded within this bilayer are various proteins, including transport proteins necessary for active transport.
• Sodium ions, for instance, must be transported across this lipid bilayer to maintain cellular functions like osmotic balance and electrical excitability.

Without the strategic operation of active transport mechanisms, many essential cellular functions could not be performed efficiently, highlighting the importance of both the membrane's structure and its associated proteins.