A Level Biology Practice Exam

Which characteristic defines an amylose molecule?

1. A branched structure with many branches

2. Long straight chains of alpha glucose molecules

3. A complex structure that forms glycoproteins

4. Rapidly breaking down into glucose units

The correct answer is: Long straight chains of alpha glucose molecules

An amylose molecule is defined by its long, straight chains of alpha-glucose units. This linear structure is a key feature of amylose, which is one of the two components of starch. The alpha-glucose molecules are linked together by 1,4 glycosidic bonds, resulting in an unbranched polymer that allows for the formation of a helical structure. This configuration enables amylose to serve as an important energy storage molecule in plants, as it can compact tightly, forming granules that are less soluble in water compared to its counterpart, amylopectin, which has a branched structure. The other options describe characteristics that do not apply to amylose. For instance, a molecule with a branched structure with many branches pertains more to amylopectin. A complex structure that forms glycoproteins refers to proteins with carbohydrate attachments, which is unrelated to the structure or function of amylose. Lastly, while amylose can eventually break down into glucose, the description of rapidly breaking down into glucose units is more applicable to simpler carbohydrates or starches as a whole, rather than reflecting the specific characteristics of amylose itself.