Silicate tetrahedron. A siliconâoxygen tetrahedron is the Si O 4 anionic group, or a silicon atom with four surrounding oxygen atoms arranged to define the corners of a tetrahedron. This is a fundamental component of most silicates in the Earth's crust. siliconâoxygen tetrahedron is the Si O 4 anionic group, or a silicon atom with four surrounding oxygen atoms arranged to define the corners of a tetrahedron.
Best Answer: G proteins are special proteins that help plasma membrane receptors work. Many different signal molecules use G-protein linked receptors, including epinephrine and other hormones. It is part of a second messenger system. How it works is that some chemical messenger binds to the receptor at the membrane.
Many different mammalian cell-surface receptors are coupled to a trimeric signal-transducing G protein. As noted earlier, ligand binding to these receptors activates their associated G protein, which then activates an effector enzyme to generate an intracellular second messenger (see Figure 20-3a).