Lipids, Fats, and Biochemistry

Fat is an essential part of our diet and is important for good health.

fat is the major storage form of energy in the body. These are found in plant foods and fish. Fats help in the absorption of fat-soluble vitamins A, D, E, and K. 

So, the correct option is ‘Fats yield the double amount of energy yielded by glucose on oxidative breakdown’.

Fats (lipids) are highly variable in their composition and structure across different animal species, reflecting specific dietary and environmental adaptations, whereas proteins and carbohydrates are more conserved.

Lipase catalyzes the hydrolysis of triglycerides (fats) into glycerol and three fatty acid molecules.

Essential fatty acids, or EFAs, are fatty acids that humans and other animals must ingest because the body requires them for good health but cannot synthesize them. Two essential fatty acids, linolenic and linoleic acid, cannot be synthesized in the body and must be obtained from food. These basic fats, found in plant foods, are used to build specialized fats called omega-3 and omega-6 fatty acids.

Fatty acids are long, straight chain carboxylic acids. A fat molecule is formed when three fatty acids molecules combine with one glycerol molecule to yield a triglyceride (another name for fat) along with three water molecules. Fats are not easily digested and are transported and stored as triglycerides.

• Coconut oil is a source of fat obtained from plants, while rest all i.e. butter, cream, and cod liver oil are obtained from animals. Thus option C is the correct answer. 

Lipids are a group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E, and K), monoglycerides, diglycerides, triglycerides, phospholipids, and others. They are the most calorigenic among the biomolecules. Chemically lipids are hydrophobic.

The predominant lipids present in the biomembrane are phospholipids, having a polar water soluble phosphorous head and a non polar long aliphatic tail. The polar head is exposed on the surface while the hydrophobic tail remains buried inside.

The cuticle is the waxy layer present on the epidermis of the leaf which curtails the rate of water loss by transpiration in certain higher plants. 
Cutin is especially noticeable in many fruits, e.g., apple, nectarine, and cherry, which can be buffed to a high gloss. Carnauba wax is derived from the cuticles of the leaves of Copernicia cerifera, a Brazilian palm.
Suberin is the inert waxy substance which is present in the cell wall of cork tissue.

Lipids (fats and oils) are compounds of carbon, hydrogen and oxygen where ratio of hydrogen and oxygen is less than that of the water. Lipids are esters of fatty acids and alcohol which form emulsion with water but are soluble in organic solvents. They are esters of three molecules of fatty acids and one molecule of trihydric alcohol glycerol, e.g., ghee, butter, cholesterol, carotene, eucalyptus oil. 

The vitamin essential for synthesis of lipids is biotin.
Biotin is required for carboxylase enzymes that are important in the metabolism of fatty acids and amino acids. Thus it acts like a coenzyme in the metabolism of fatty acids (types of molecules found in fats and oils).

The energy content is approximately 4 kcal/g for carbohydrates, 4 kcal/g for proteins, and 9 kcal/g for fats. The ratio is roughly 1:1:2.

Energy storage molecules are those molecules which store energy in the form of covalent chemical bonds. Some molecules like glycogen (carbohydrate) and triglycerides (lipids) are synthesized by the cells and they are stored for the later release of energy. So, the correct answer is "both lipids and carbohydrates".