OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

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Get ready for the OCR GCSE Biology exam with our comprehensive quiz, featuring flashcards and multiple choice questions. Understand the exam format, key topics, and effective study strategies to excel.

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What is the special shape of guard cells that allows them to function effectively?

  1. Flat

  2. Cylindrical

  3. Square

  4. Kidney

The correct answer is: Kidney

The unique shape of guard cells, which resemble a kidney, is crucial for their function in regulating gas exchange in plants. This kidney-like shape allows guard cells to swell and become turgid when water enters them, creating a curvature that opens the stomata. This opening is essential for facilitating the entry of carbon dioxide for photosynthesis and for allowing the release of oxygen and water vapor. When water is scarce, guard cells lose turgor pressure and become flaccid, which causes the stomata to close, thereby conserving water. This ability to change shape based on water availability plays a critical role in the plant's overall water management and in regulating gas exchange, making the kidney shape particularly effective for their role in plant physiology.