Concept explainers
A.
To write: An equation to describe the working of transporter that mediates the transport of a solute down its concentration gradient.
Introduction: Transporter enhances the movement of most small, water-soluble, organic molecules and some inorganic ions across the cell membrane. The cell membrane contains transporter that brings nutrient such as sugar, amino acid, as like enzymes bind with substrate molecule.
A.
Explanation of Solution
Transporters are highly selective toward the solute and sometimes they allow single molecules to transport. An analogous equation shown below describes the movement of a solute mediated by a transporter.
In equation (1), T is denoted by transporter, S is denoted by solute, S* is the solute on the opposite side of the membrane where the solute molecule is same but it is located in different atmosphere.
B.
To explain: The function of a transporter from the above given equation (1).
Introduction: Transporter enhances the movement of most small, water-soluble, organic molecules and some inorganic ions across the cell membrane. The cell membrane contains transporter that brings nutrient such as sugar, amino acid, as like enzymes bind with substrate molecule.
B.
Explanation of Solution
Equation (1) is useful as it represents the binding step followed by a delivery step. It is similar to the mathematical treatment explained for enzymes. In this equation, KM value describes the transporters that represents their empathy for the solute and Vmax value that explains the supreme rate of relocation during transport. To deliver the accurate conformational changes during the transport across the membrane, the following equations shall be given:
In the above equations, T* represents the transporter after the respective conformational changes that show its solute binding area on the opposite portion of the membrane. Equation (3) represents that after conformational changes, the transporter returns to its starting conformation. In the cell’s plasma membrane, the transporter acts as the pathways of transportation of molecular elements across cell and also in mitochondrial membrane.
C.
To explain: The equation (1) is an inappropriate description of channel function.
Introduction: Transporter enhances the movement of most small, water-soluble, organic molecules and some inorganic ions across the cell membrane. The cell membrane contains transporter that brings nutrient such as sugar, amino acid, as like enzymes bind with substrate molecule.
C.
Explanation of Solution
In equation (1), the transporter is to guide and propel the complex traffic of solute into and out of the cell through transportation pathway between the cytosol and different membrane-bound organelles. In this equation, neither the channel nor the behavior of channel is described. When solutes are transported through the membrane, it binds with the transporter. However, in the case of transportation through channels, the solutes do not bind with any transporter.
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Chapter 12 Solutions
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