Phosphoinositides are a class of phospholipids that are formed from phosphatidylinositol.  Seven types of phosphoinositides exist:

- phosphatidylinositol 3-phosphate (PI3P)
- phosphatidylinositol 4-phosphate (PI4P)
- phosphatidylinositol 5-phosphate (PI5P)
- phosphatidylinositol 4,5-bisphosphate (PI4,5P2)
- phosphatidylinositol 3,5-bisphosphate (PI3,5P2)
- phosphatidylinositol 3,4-bisphosphate (PI3,4P2)
- phosphatidylinositol 3,4,5-trisphosphate (PIP3)

These molecules collectively make up less than 1% of all lipids, but they function as important mediators of cell growth and development as well as membrane signaling and trafficking.  

Phosphoinositides

Plasma membranes across different cell types contain unique phospholipids characterized by specific fatty acid compositions. Phospholipid-derived fatty acid analysis (PLFA) is a biochemical technique that utilizes these specific profiles to identify distinct types of cells, as archaea, bacteria, and eukaryotes each possess a unique PLFA signature.

Phospholipid-Derived Fatty Acid Analysis (PLFA)

Due to their amphipathic nature, phospholipids spontaneously assemble into energetically stable structures in aqueous environments. While their polar heads are attracted to water, their long, nonpolar tails are excluded from water and strongly attracted to one another. This causes the hydrophobic tails to congregate within enclosed areas, shielded from water by the hydrophilic heads. Common arrangements include micelles, lipid-bilayer sheets, and lipid-bilayer spheres.

Unique Phospholipid Structures

Phospholipids are complex lipids composed of a glycerol backbone linked to two hydrophobic, nonpolar fatty acid tails and a hydrophilic, polar head group containing a negatively charged phosphate. The two fatty acid tails can be both saturated, both unsaturated, or one of each. The hydrophilic head group can also feature a more complex polar moiety, which is represented by an 'R' designation.

University of Southern Mississippi

Google

Michigan State University

There are different types of lipids which include:

- Fatty Acids 
- Triacylglycerides
- Isoprenoids 
- Sterols
- Phospholipids

Diversity of Lipids

Complex lipids are lipid molecules that contain at least one additional chemical component beyond fatty acids and glycerol, such as a phosphate group or a carbohydrate moiety.

Complex Lipids

https://openstax.org/details/books/microbiology/

Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

Microbiology is produced through a collaborative publishing agreement between OpenStax and the American Society for Microbiology Press. The book aligns with the curriculum guidelines of the American Society for Microbiology.

OpenStax Microbiology Textbook

Fatty acids are lipids that contain long-chain hydrocarbons that end with a carboxylic acid functional group. Fatty acids tend to have a nonpolar or hydrophobic chain.

Fatty Acids

Simple lipids are lipid molecules formed from only two types of chemical compounds: glycerol and fatty acids.

Simple Lipids

Glycolipids are complex lipids in which carbohydrate groups (sugars) are covalently bonded to the polar head groups of the lipid molecules.

Glycolipids

Triglycerides (also known as triacylglycerols) are simple lipids formed by chemically linking three fatty acid chains to a single glycerol molecule. Because all three substituents on the glycerol backbone are long hydrocarbon chains, these compounds are nonpolar and hydrophobic, meaning they are not attracted to polar water molecules and are insoluble in aqueous environments. They serve as the primary components of adipose tissue and sebum, and function as highly efficient energy-storage molecules.

Triglycerides

Phospholipids

Waxes are a class of lipids that are typically water-resistant and solid or hard at room temperature. They soften when heated and liquefy when sufficiently warmed.

Waxes

Isoprenoids, also known as terpenoids, are branched lipids formed by the chemical modification of isoprene molecules. They play diverse physiological roles in plants and animals, and have technological uses as pharmaceuticals (such as capsaicin), pigments (such as beta-carotene and xanthophylls), and fragrances (such as menthol, camphor, limonene, and pinene). Long-chain isoprenoids are also found in hydrophobic oils and waxes.

Isoprenoids (terpenoids)

Steroids are complex, ring-structured lipids found in cell membranes, with some members functioning as chemical messengers or hormones.

Learn Before

Related

Learn After