Self-reflection lipids (Neil)

Last Monday, 2^nd December 2019, I have learned about lipids. Some of the contents are quite general and the rest of it is the new contents. Well, as they say, we learn something new every day. From the Biochemistry lecture by Dr Dayang, I have learned that lipids are biomolecules that are soluble in organic solvents. Lipids perform three biological functions. Firstly, lipids containing hydrocarbon side chains serve as energy storage. Secondly, lipids in the form of bilayer are essential components of biological membranes. Finally, lipids act as intra and intercellular signalling molecules. There are two types of lipids based on polarity which are non-polar lipids and polar lipids. Lipids are further classified into several groups such as fatty acids, triglycerides, glycerophospholipids, sphingolipids and isoprenoids. 

One of the lipids that I have learned is fatty acids. Fatty acids that are predominant in plants and animals are C16 and C18. Saturated chains pack tightly and form more rigid, organized aggregates while unsaturated chains bend and pack in less ordered way, with greater potential for motion. Next are triglycerides. Fatty acids are triesters of glycerol and most contain two or three different types of fatty acid residues. The roles of triglycerides are it functions as energy storage, insulation and saponification. Other than that, glycerophospholipids are the major lipid component of biological membranes. These are amphipillic molecules with non-polar aliphatic tails and polar phosphoryl-X heads. Moreover is phospholipids which can be degraded at various point, depending on the enzymes used. Furthermore are sphingolipids which are major membrane components. They are derivative of the C18 amino alcohol sphingosine. Some examples of sphingosine are sphingomyelins, cerebrosides and gangliosides. 

Besides that, steroids are biomolecules with three 6-membered rings and one 5-membered ring that are all fused together. Cholesterol is the most common steroids in animals and precursors for all other steroids in animals. Next, terpenes are major biosynthetic building blocks within nearly every living creature. Terpenes are derived biosynthetically from units of isoprene. Terpenes have several biological functions such as color and odors associated with plants, vitamin and precursors, visual pigments and chloroplast pigments. Furthermore, eicosanoids are signalling molecules made by oxidation of C₂₀ essential fatty acids. Eicosanoids exert complex control over mainly bodily systems, mainly in inflammation or immunity and as messengers in the central nervous system. Four families of eicosanoids are prostaglandins, prostacyclins, thromboxanes and leukotrienes. Finally, there are some vitamins are lipid soluble which are vitamins A, D, E and K.

What I learned after that is about membranes and transport across membrane. Membrane proteins are components of biological membranes. They have several functions such as catalyse reactions, mediate the flux of nutrients and wastes and participating in relaying external information to the cell. There are several types of membrane proteins such as transmembrane proteins, integral membrane proteins, peripheral membrane proteins, integral monotopic proteins and lipid-linked proteins. Next, transport across membranes which can be classified into two categories which are passive-mediated of facilitated diffusion and active transport. Facilitated diffusion is passive transport that is facilitated by integral proteins and it does not requires ATP. Active transport however is the movement of a substance against its concentration gradient and it requires ATP. The most well-known example of this transport system is sodium-potassium pump. Lastly, signal transduction is the process by which an extracellular signalling molecules activates a membrane receptor that in turns alters intracellular molecules creating a response and it involves transmembrane proteins.