Ohio Assessment for Educators (OAE) Integrated Science (024) Practice Exam

How does osmotic pressure function in the body?

1. By pushing water out of cells

2. By drawing fluid back in from surrounding tissues

3. By supplying energy for active transport

4. By maintaining blood pH levels

The correct answer is: By drawing fluid back in from surrounding tissues

Osmotic pressure is a fundamental concept in biology and physiology, especially regarding fluid balance in the body. It refers to the pressure required to prevent the flow of water across a semipermeable membrane due to solute concentration differences. In the body, osmotic pressure plays a crucial role in maintaining hydration and the distribution of fluids between blood vessels and surrounding tissues. The correct answer highlights the effect of osmotic pressure in drawing fluid back into the circulatory system from the surrounding tissues. This process is primarily driven by the presence of proteins, such as albumin, in the blood plasma. These proteins create a higher solute concentration in the blood compared to the interstitial fluid, leading to an osmotic gradient. Water moves from an area of lower solute concentration (the surrounding tissues) to an area of higher solute concentration (the blood) to equalize the concentration, effectively drawing fluid back into the bloodstream. This mechanism is essential for maintaining blood volume and pressure, as well as ensuring that tissues receive adequate hydration and nutrients. It also helps prevent edema, which can occur if fluid accumulates excessively in the tissues. The ability of osmotic pressure to influence fluid movement is crucial for homeostasis and overall health.