Q.14 Active transport is required for
1. positively charged molecules
2. neutral molecules
3. negatively charged molecules
4. chloride ions
Active transport moves molecules or ions against their concentration gradient using cellular energy like ATP, and it’s essential for ions such as chloride that need precise cellular regulation.
The correct answer is 4. chloride ions.
Correct Answer
4. chloride ions
Chloride ions (Cl-) are negatively charged and actively transported against electrochemical gradients by specific pumps like the Na+/K+/2Cl- cotransporter or Cl-/HCO3- exchangers, maintaining cellular pH and volume. This primary or secondary active transport uses ATP directly or via gradients from Na+/K+ ATPase.
Option Explanations
| Option | Description | Why Incorrect/Correct |
|---|---|---|
| 1. positively charged molecules | Cations like Na+, K+, Ca2+ moved by ion pumps (e.g., Na+/K+ ATPase). | Incorrect: While true for many positives, not exclusive; question targets specific need like Cl-. |
| 2. neutral molecules | Uncharged solutes like glucose via SGLT (secondary active). | Incorrect: Most neutrals use facilitated diffusion or secondary; pure active rare without charge gradient. |
| 3. negatively charged molecules | Anions generally; includes Cl- but broad. | Partially correct but vague; Cl- exemplifies via dedicated systems unlike generic anions. |
| 4. chloride ions | Anionic Cl- requiring uphill transport for homeostasis. | Correct: Cl- demands active influx/efflux (e.g., NKCC1 cotransporter) against membrane potential. |
Biological Role
Active transport sustains ion balances vital for your microbiology studies, like osmotic regulation in bacteria or neurons. Examples: Gastric HCl secretion uses H+/K+ ATPase coupled to Cl-. Outliers (>90% in allowed regions) validate real structures.
