Final answer:
The glomerulus is permeable to small substances but not to macro molecules like large proteins, as the filtering mechanism, which includes fenestrations and the basement membrane, restricts their passage.
Step-by-step explanation:
The glomerulus, a cluster of capillaries in each nephron of the kidney, is responsible for filtering the blood. Its selective permeability is facilitated by structures known as fenestrations, pores within the capillary endothelial cells. These fenestrations allow substances smaller than 4 nm to pass freely and filter out most constituents up to 8 nm, while they restrict larger components like macro molecules, which includes cells and large proteins.
The negatively charged proteins around these pores typically repel negatively charged substances and allow positive ones to pass more effectively. Additionally, the basement membrane serves as another barrier to prevent medium-to-large proteins such as globulins from filtering through. This intricate filtering mechanism ensures that the final filtrate lacks cells or large proteins. Therefore, the statement 'The glomerulus is permeable to macro molecules' is false as the filtration system of the glomerulus is designed to prevent such large molecules, including most proteins, from passing into the filtrate.
This selective permeability plays a crucial role in the formation of the renal filtrate, which does not contain macro molecules such as blood cells and large proteins, ensuring the efficient function of the kidneys in filtering waste from the bloodstream and maintaining the body’s fluid and electrolyte balance.