cone photoreceptor outer segment

Definition

Target type: cellularcomponent

The outer segment of a vertebrate cone photoreceptor that contains membrane discs that are contiguous with the ciliary membrane and containing opsin photoreceptor proteins. [GOC:krc, GOC:pde, PMID:19501669, PMID:26574505, PMID:6771304]

The cone photoreceptor outer segment is a specialized structure that contains the molecular machinery for capturing light and converting it into electrical signals. It is composed of a stack of flattened, membrane-bound discs, known as the lamellae, which are embedded in a matrix of proteins. The discs are tightly packed, creating a highly organized structure that maximizes light absorption. The outer segment is also rich in lipids, which provide structural support and facilitate the movement of molecules within the membrane.

The lamellae are the sites of light absorption, and they contain the light-sensitive pigment rhodopsin in rods and photopsin in cones. Rhodopsin and photopsin are G protein-coupled receptors that undergo a conformational change upon absorbing light, initiating a signal transduction cascade that ultimately leads to the generation of an electrical signal.

The outer segment is connected to the inner segment of the photoreceptor by a structure called the connecting cilium, which allows for the transport of nutrients and other molecules. The outer segment is constantly being renewed, with the oldest discs being shed at the tip and new discs being added at the base. This process ensures that the outer segment remains functional and sensitive to light.

The cellular components of the cone photoreceptor outer segment include:

* **Lamellae:** Flattened, membrane-bound discs that contain the light-sensitive pigment.
* **Rhodopsin or Photopsin:** G protein-coupled receptors embedded in the lamellae that absorb light and initiate signal transduction.
* **Lipids:** Provide structural support and facilitate molecular movement within the membrane.
* **Connecting cilium:** Connects the outer segment to the inner segment, allowing for the transport of nutrients and other molecules.
* **Proteins:** Provide structural support and facilitate signal transduction.
* **Enzymes:** Involved in the synthesis and degradation of rhodopsin/photopsin and other molecules.

The highly specialized structure of the cone photoreceptor outer segment is essential for the process of vision. Its ability to capture light and convert it into an electrical signal allows us to perceive the world around us.'
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Proteins (1)

Compounds (1)