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Substance 'X' is the charged molecule of...

Substance 'X' is the charged molecule of small molecular weight . It is found at higher concentrations outside of cells than inside . How can substance 'X' entre the cells ?

A

Active transport

B

Diffusion through a channel

C

Diffusion through lipid bilayer

D

None of the above

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To determine how substance 'X', a charged molecule of small molecular weight, can enter cells where its concentration is higher outside than inside, we can analyze the options provided: ### Step-by-Step Solution: 1. **Identify the Nature of Substance 'X':** - Substance 'X' is described as a charged molecule with a small molecular weight. This indicates that it is likely a polar molecule. 2. **Understand the Concentration Gradient:** - The problem states that substance 'X' is found at higher concentrations outside the cell than inside. This means that substance 'X' will naturally move from an area of high concentration (outside) to an area of low concentration (inside) if allowed to do so. 3. **Evaluate the Transport Mechanisms:** - **Active Transport:** This process requires energy (ATP) and usually moves substances against their concentration gradient (from low to high concentration). Since substance 'X' is moving from high to low concentration, active transport is not applicable here. - **Diffusion through a Channel (Facilitated Diffusion):** This mechanism allows polar or charged molecules to pass through the cell membrane via specific protein channels. Since substance 'X' is charged and polar, it cannot easily cross the lipid bilayer directly and would require a channel to facilitate its movement. - **Diffusion through Lipid Bilayer:** Non-polar molecules can diffuse through the lipid bilayer without assistance. However, since substance 'X' is charged and polar, it cannot pass through the lipid bilayer directly. - **None of the Above:** This option would imply that none of the previous mechanisms apply, which is incorrect in this case. 4. **Conclusion:** - The most appropriate mechanism for substance 'X' to enter the cell is through **diffusion via a channel (facilitated diffusion)**, as it allows the charged molecule to move down its concentration gradient without the need for energy. ### Final Answer: Substance 'X' can enter the cells through **diffusion through a channel (facilitated diffusion)**. ---
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