5 (a) Apple trees show genetic variation - Edexcel - GCSE Biology Combined Science - Question 5 - 2023 - Paper 1

The term for an observable characteristic is D phenotype.

The type of reproduction that produces genetically identical organisms is asexual reproduction.

An advantage of growing genetically identical apple trees is that they will have the same desired qualities, such as consistent fruit flavor. A disadvantage is that they can be susceptible to specific diseases, leading to potential crop failure.

1. Prepare a series of solutions with varying pH levels (e.g., pH 4 to pH 8).
2. Add a fixed amount of starch solution to each pH solution.
3. Introduce the enzyme solution to each mixture and incubate for a set period.
4. After incubation, add iodine solution to each mixture to test for starch presence.
5. The optimum pH is where the starch is most efficiently broken down, indicated by the least amount of blue-black color after iodine is added.

Enzymes have specific pH ranges within which they function optimally. At pH 10, the environment is too alkaline, which can lead to denaturation of the enzyme's active site. This change disrupts the enzyme's ability to bind to starch and catalyze its breakdown.