Lipids, Fats, and Biochemistry

Glycerophospholipids, usually referred to as phospholipids, are ubiquitous in nature and are key components of the lipid bilayer of cells, as well as being involved in metabolism and cell signaling.

High-density lipoproteins (HDL) collect fat molecules (phospholipids, cholesterol, triglycerides, etc.) from the body's cells/tissues, and take it back to the liver. HDLs are sometimes referred to as good lipoprotein because higher concentrations correlate with low rates of atherosclerosis progression.

Eicosapentaenoic acid is an omega-3 fatty acid. It is obtained in the human diet by eating oily fish or fish oil, e.g. cod liver, herring, mackerel, salmon, menhaden and sardine, and various types of edible seaweed. It is also found in human breast milk.

Steroids are structurally different from the other lipids. The carbon skeleton of steroids is bent to form four fused rings that do not contain fatty acids. The most common steroid, cholesterol, is needed to make both the male (testosterone) and female (estrogen) sex hormones.

Rumenic acid is a conjugated linoleic acid found in the fat of ruminants and in dairy products. It is an omega-7 trans fat.

Phospholipases are enzymes that release fatty acids from the second carbon group of glycerol. This particular phospholipase specifically recognizes the sn-2 acyl bond of phospholipids and catalytically hydrolyzes the bond releasing arachidonic acid and lysophospholipids.

Glycitein is an O-methylated isoflavone which accounts for 5-10% of the total isoflavones in soy food products. Glycitein is a phytoestrogen with weak estrogenic activity, comparable to that of the other soy isoflavones.

 Accumulation of lipids in arteries causes reduced blood supply to the heart due to the formation of  atheromatous plaques [lipids,macrophages] and this condition may give rise to heart attack and  is termed as atherosclerotic heart disease.

Rough Endoplasmic Reticulum (RER) appears rough under the microscope because ribosomes are attached to its outer surface. Ribosomes are the protein-synthesizing machinery that give RER its characteristic textured appearance.

Leucoplasts are a category of plastid and as such are organelles found in plant cells. They are non-pigmented, in contrast to other plastids such as the chloroplast.

The plasma membrane is composed mainly of phospholipids (lipids) and proteins, arranged in the fluid mosaic model. Lipids form the basic bilayer structure, while proteins perform functions like transport, signaling, and enzymatic activity. Carbohydrates are present but are attached to proteins or lipids, not a major component.

Cholesterol is a fatty alcohol (sterol) found in animal fats and cell membranes. It is not related to chlorine (A), chlorophyll (B), or blood sugar (D). Cholesterol is essential for hormone production and cell membrane structure in animals.

Bile emulsifies fats, breaking large fat globules into smaller droplets to increase surface area for lipase enzymes to act upon. This emulsification is crucial for fat digestion and absorption. Bile does not act on proteins (broken down by proteases), carbohydrates (broken down by amylases), or esters.

Carnitine is essential for transporting long-chain fatty acyl groups across the inner mitochondrial membrane. The carnitine shuttle converts fatty acyl-CoA to fatty acylcarnitine, transports it across, then regenerates fatty acyl-CoA inside for beta-oxidation.

Cycloartenol is an important type of stanol found in plants. The biosynthesis of cycloartenol starts from the triterpenoid squalene. It is the first precursor in the biosynthesis of other stanols and sterols.