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

What adaptation allows palisade leaf cells to be efficient in photosynthesis?

1. A flattened shape for exposure to light

2. A thick cuticle to prevent water loss

3. Red coloration to capture more light

4. A high number of stomata for gas exchange

The correct answer is: A flattened shape for exposure to light

Palisade leaf cells are specialized cells found in the leaves of plants, and their primary function is to perform photosynthesis efficiently. The key adaptation that facilitates this process is their flattened shape. This structure maximizes the surface area exposed to sunlight, allowing more light to be intercepted and absorbed by the chlorophyll present in the chloroplasts within the cells. This increased light absorption is crucial for photosynthesis, as light energy is converted into chemical energy in the form of glucose. While a thick cuticle is important for reducing water loss, it does not specifically enhance photosynthesis and can, in fact, limit light penetration. Red coloration may play a role in some plants but is not a typical characteristic of palisade cells. The number of stomata is vital for gas exchange, allowing carbon dioxide to enter the leaf; however, this feature is not specific to the palisade cells themselves and does not directly enhance photosynthesis in the same way that the cell's shape does.