Tag: lipids

Fats are an important class of biomolecules.They are compounds of carbon, hydrogen and oxygen where the ratio of hydrogen and oxygen is less than that of water. Lipids are a concentrated source of energy and serve for long term energy storage in body of animals and plants. Their respiratory quotient is less than one. Approximately 9 calories are provided by one gram of fat as compared to 4 by carbohydrates. Fats also act as insulating material because they are poor conductors of heat. Most of the animals have a layer of fat below the skin acting as insulating material. Lipids also serve as structural biomolecules for example conjugate lipid molecules like phospholipids, glycolipids, sphingolipids etc.

Vitamin A, testosterone and UV rays induce lysis of lysosomal membrane under acidic pH which makes options B, C and D incorrect. Cholesterol exhibit scavenging effect on free radicals as well as prevent osmotic rupture of lysosomal membrane which makes option A correct answer. 

Glycogen is also homopolysaccharide of D-glucose and serves as an energy storing molecule in animals as glucose as storage material can increase the osmotic pressure of storage cell enormously. Proteins do not serve as energy storage molecule. Fat and oil are storage lipids and are derivatives of hydrocarbon that produce enormous energy upon oxidation. Thus, the correct answer is B.

Lipids are broken down in the digestive tract to form fatty acids and cholesterol. Fatty acids and cholesterol are key components of cell membranes that regulate its fluidity and permeability. Lipids of the nervous system are localized in myelin sheaths thereby providing electrical insulation. Thus the correct answer is option D.

Lecithin is a group of yellow-brownish fatty substances present in animal and plant tissues.In the pharmaceutical industry, it is used in emulsifications and encapsulation of drugs and is a good dispersing agent. Thus the correct answer is option A.

Phosphatidylethanolamines are phospholipids found in all living cells, They are found mainly in the nervous tissue such as the white matter of the brain, nerves, neural tissue and in the spinal cord. 

Membrane biogenesis is structuring/rebuilding/repairing of the cell membrane. As the cell membrane is made of a bilayer of phospholipids embedded with proteins.It is a process carried out by the cell with the help of smooth endoplasmic reticulum (SER) and Golgi apparatus (GA). Where the SER synthesizes lipids which are added with phosphate group and modified to phospholipids by the process of phosphorylation in the GA and transported through vesicles to the cell membrane.

De novo synthesis of cholesterol from acetyl-CoA takes place in the liver. Cholesterol is an essential metabolite for the normal functioning of the endocrine system, regulation of cell membrane processes, and absorption of dietary lipids. They are important structural components of membranes. Cholesterol also serves as precursor for the synthesis of steroid hormones, vitamin D, and bile salts which are important in fat absorption from the small intestine into the blood circulatory system and secretion of liver waste products through feces. Thus the correct answer is option B.

Commonly candles are prepared from stearic acid and paraffin wax. Candles that made from paraffin wax only burn quicker than those made from paraffin wax and stearic acid together.