The G-proteins associated with the intracellular terminal of a GPCR dissociate when the change in conformation of the G-protein allows for a GTP to replace a GDP bound to the G-protein. ATP and ions are not at play here, nor is there degradation of the receptor's intracellular tail. It is the binding of GTP alone that triggers the cascading results of the protein's activation.

TLRs are transmembrane receptors that have an extracellular leucine-rich region that recognize PAMPs. Recognition of a pathogen factor causes the intracellular toll-interleukin-1 domain to bind adaptor proteins to induce expression of genes responsible for initiating an innate immune response. 

Paracrine signaling refers to close range cell to cell signaling. This is different from endocrine signaling in which signaling molecules (hormones) are released into the blood stream in order to communicate with distant cells.

Autocrine signaling is a type of signaling in where the signaling molecule and the receptor for that messenger are found on the same cell. Cell signaling across a synapse is called synaptic signaling. 

Blood is an aqueous solution and will easily dissolve polar, hydrophilic molecules. Nonpolar molecules, however, do not easily exist in this solution and require a bound polar group, such as a carrier protein, to exist in equilibrium.

Proteins, carbohydrates, and nucleic acids all contain polar groups, allowing them to dissolve in the blood. Lipids, however, are nonpolar and require transport proteins. Steroids are a class of lipids and will require protein assistance for transport in the blood.

Sucrose is a carbohydrate, glycine is a polar amino acid, and ATP is a polar nucleic acid derivative.

Amphipathic molecules contain both polar and nonpolar regions, making them an extremely diverse class with an array of functions. For example, bile is an amphipathic molecule whose nonpolar region interacts with fats and whose polar region interacts with the aqueous environment of the small intestine.

Most lipids are entirely nonpolar and hydrophobic. Phospholipids, however, are formed from a glycerol molecule bound to two hydrophobic fatty acid tails and a hydrophilic phosphate head. This structure allows phospholipids amphipathic properties. Most notably, phospholipids are able to interact with the aqueous environments in the cell cytosol and extracellular environment, while maintaining the hydrophobic region of the cell membrane that acts as a semipermeable barrier.

Triglycerides are considered nonpolar. Glutamate is an acidic amino acid with highly polar properties. Maltose is a six-carbon sugar (carbohydrate) and is highly polar.

Lipids have a variety of functions in the human body, one of which is the storage of energy for later use. This function is accomplished by triglycerides (also called triacylglycerols), which belong to the class of glycerolipids.

Fatty acids synthesized in the human body always have an even number of carbon atoms usually between 12 and 28. Odd-numbered fatty acid chains will occasionally be found in plants and marine animals.

A phospholipid is made up of two fatty acids and a phosphate group with an R-group attached to a glycerol backbone. The phosphate group allows for one end of the molecule to be polar while the fatty acids allow for the other part to be nonpolar. Phospholipids are a major component of the bilayered cellular membrane 

Carbohydrate monomers (monosaccharides) can be joined together with either alpha or beta linkages. Humans have the enzymes necessary in order to break down alpha linkages, but not beta linkages. Cellulose is a polysaccharide in which the monomers joined together by beta linkages, so humans cannot digest cellulose. Some bacterial species are capable of cleaving these linkages and have developed symbiotic or mutualistic relationships with animals. These bacterial species inhabit the mammalian digestive tract, cleaving beta linkages and gaining protection from the outside environment.

The size and branching pattern of a carbohydrate do not affect its ability to be digested.

The two most common polysaccharides found in plant cells are starch and cellulose. Starch is the primary source of energy storage, while cellulose is used to construct the plant's cell walls.