One critical function of chondroitin sulfate is to act as a...

Name: Problem 22, Chapter 7: Lehninger Principles of Biochemistry
Uploaded: 2021-01-14T13:12:39-08:00
Duration: 1 min 45 s
Channel: Alexander Cheng
Description: One critical function of chondroitin sulfate is to act as a lubricant in skeletal joints by creating a gel-like medium that is resilient to friction and shock. This function seems to be related to a distinctive property of chondroitin sulfate: the volume occupied by the molecule is much greater in solution than in the dehydrated solid. Why is the volume so much larger in solution?

One critical function of chondroitin sulfate is to act as a lubricant in skeletal joints by creating a gel-like medium that is resilient to friction and shock. This function seems to be related to a distinctive property of chondroitin sulfate: the volume occupied by the molecule is much greater in solution than in the dehydrated solid. Why is the volume so much larger in solution?

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Key Concepts

Electrostatic Repulsion in Polyelectrolytes

Chondroitin sulfate is a polyelectrolyte, meaning it has multiple ionizable groups along its chain. In solution, these equally charged groups repel each other, causing the molecule to unfold and assume an expanded conformation. This electrostatic repulsion is a key factor in the significant volume increase observed in its hydrated state.

Hydration of Charged Molecules

In aqueous solution, the numerous negatively charged sulfate groups on chondroitin sulfate attract water molecules. This interaction leads to the formation of a hydration shell around the polymer, which effectively increases the size of the molecule by holding a large amount of water. The resulting structure occupies much more volume in solution compared to the compact dehydrated solid.

Polymer Swelling and Gel-like Behavior

The combined effects of hydration and electrostatic repulsion lead to the swelling of chondroitin sulfate in solution, which is crucial for its role in joint lubrication. The extended, gel-like structure formed in this state provides resilience against friction and shock, illustrating how physical chemistry properties of polymeric molecules contribute to biological functions.

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