Final answer:
The pentose sugar found in the heart muscle is ribose, a component of RNA, and not deoxyribose, which is present in DNA.
Step-by-step explanation:
The pentose sugar present in the heart muscle is ribose. This is due to the fact that ribose is a component of ribonucleic acid (RNA), which plays a crucial role in the synthesis of proteins and various enzymatic functions within all living cells, including those of the heart muscle.
In contrast, deoxyribose is the pentose sugar found in DNA, and glucose and fructose are examples of hexose monosaccharides, which have six carbon atoms in their structure.