Final answer:
In hemodialysis, the semipermeable membrane allows the passage of small waste products like creatinine, urea, excess sodium, and glucose, but red blood cells and bacteria, being larger, do not pass through this membrane.
Step-by-step explanation:
During hemodialysis, certain substances are allowed to pass through a semipermeable membrane to cleanse the blood. The substances that can pass through the membrane include creatinine, urea, excess sodium, and various other small waste products. Glucose is also small enough to pass through the membrane. However, elements such as red blood cells (RBCs) and other larger structures like bacteria are too large to pass through this membrane and therefore remain in the blood.