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Movement in and out of Cells - Active transport

Grade 11IGCSEBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Active transport is the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration (against a concentration gradient) using energy from respiration.

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It requires specific carrier proteins embedded in the cell membrane that act as pumps to move substances across.

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The energy required for active transport is provided in the form of ATPATP (Adenosine Triphosphate), primarily produced during aerobic respiration in the mitochondria.

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Factors that decrease the rate of respiration, such as a lack of O2O_2 or low temperature, will also decrease the rate of active transport.

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In plants, root hair cells use active transport to absorb mineral ions like nitrate ions (NO3−NO_3^-) and magnesium ions (Mg2+Mg^{2+}) from the soil where their concentration is lower than inside the cell.

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In humans, active transport is used in the small intestine (villi) to absorb glucose and amino acids into the blood even when their concentration in the gut is low.

📐Formulae

C6H12O6+6O2→6CO2+6H2O+Energy (as ATP)C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy (as } ATP)

Direction of Movement: [Low]→[High]\text{Direction of Movement: } [\text{Low}] \rightarrow [\text{High}]

💡Examples

Problem 1:

A root hair cell is placed in a solution containing 0.05 mmol/dm30.05\, mmol/dm^3 of NO3−NO_3^- ions. The internal concentration of NO3−NO_3^- in the cell sap is 2.5 mmol/dm32.5\, mmol/dm^3. Describe the process by which the cell takes up more nitrate ions.

Solution:

The cell will use active transport to move NO3−NO_3^- ions into the cell.

Explanation:

Because the concentration of NO3−NO_3^- is higher inside the cell (2.5 mmol/dm32.5\, mmol/dm^3) than outside (0.05 mmol/dm30.05\, mmol/dm^3), the ions must move against the concentration gradient. This requires carrier proteins in the cell membrane and energy released from ATPATP via respiration.

Problem 2:

Explain why a metabolic poison that inhibits the production of ATPATP would stop the uptake of glucose in the proximal convoluted tubule of the kidney.

Solution:

The uptake of glucose relies on active transport, which is an energy-dependent process.

Explanation:

Active transport requires energy from ATPATP to change the shape of carrier proteins. If a poison inhibits ATPATP production, there is no energy available to pump glucose molecules against their concentration gradient, causing the process to cease.

Active transport - Revision Notes & Key Diagrams | IGCSE Grade 11 Biology