What is the maximum molecular weight for a substance to pass through the glomerulus?

The glomerulus is a key structure in the kidney responsible for filtering blood and forming urine. It allows the passage of certain substances based on their size and molecular weight. The maximum molecular weight that typically allows a substance to be filtered through the glomerular membrane is around 70,000 Daltons.

Substances with a molecular weight greater than this threshold, such as many proteins, are generally retained in the bloodstream and do not pass through the glomerular barrier. This important filtration function is so selective that it not only relies on size but also on other factors such as charge. The glomerular filtration barrier is more permeable to smaller molecules and those that are negatively charged.

Thus, while substances up to 70,000 Daltons can pass through the glomerulus and enter the urine, larger molecules tend to remain in circulation, making 70,000 the correct maximum molecular weight for filtration in this context.