Information on a Proton Pump in Archaebacteria

A proton pump is an integral membrane protein responsible for moving protons (subatomic particle with electric charge of +1) across cell membranes, the mitochondrion and other cellular compartments. Archaebacteria, or simply archae, is a group of single celled micro-organisms. They are prokaryotes, meaning that they lack a cell nucleus.

Introduction

• During cell respiration, the proton pump takes protons from the matrix (cell material in which specialized structures are embedded) and releases them into the inter-membrane space. This process creates a difference or gradient in pH and electrical charge, according to AbsoluteAstronomy.com. The gradient helps establish an electrochemical potential (a reservoir or battery of the cell's stored energy). Because the inner cell membrane functions to block protons from drifting back into the matrix, some sort of energy is required to begin the process.

Archaebacteria

• Archae is a big group of prokaryotes that in some respects are similar to bacteria and in some respects similar to eukaryotes (organisms that have a nucleus), according to Bio-Medicine.org. In particular, archae are like other prokaryotes in their cell structure and metabolism and are like other eukaryotes in genetic transcription (RNA synthesis) and translation (gene expression).

Function

• In archaebacteria, mitochnodria and bacteria in general, the process of photosynthesis powers the movement of protons. Specifically, archaea use a protein called bacteriorphdopsin as a proton pump. According to absoluteastronomy.com, bacteriorhodopsin is an integral membrane protein which is found on approximately 50 percent of the archaean cell. It allows archaea to capture light energy and use it to move protons across the cell membrane.

Features

• Bacteriorhodopsin was the first membrane transport protein whose structure was fully developed and studied, according to "Molecular Biology of the Cell" by Bruce Alberts. Each bacteriorhodopsin molecule contains one retinal (light-absorbing group) which provides the protein with its purple color. When exposed to a photon (a light particle), the retinal becomes excited and changes shape. This results in the transfer of one proton from the inside of the cell to the outside.

Considerations

• If exposed to bright light, each bacteriorhodopsin molecule is capable of pumping a couple of hundred protons per second, according to Alberts. The light driven transfer of protons creates a gradient across the plasma membrane. This gradient in turn drives the production of ATP (compound with large amount of chemical energy) in the cell's plasma membrane as well as other energy requiring processes in the cell. As a result, bacteriorhodopsin is a proton pump that converts solar energy into a gradient which in turn provides energy to the entire archaebacteria cell.