Lipids, Fats, and Biochemistry

In some higher plants, the cuticle is a water-impervious protective layer covering the epidermal cells of leaves and other parts and limiting water loss. It consists of cutin, a waxy, water-repellent substance allied to suberin, which is found in the cell walls of corky tissue. Cutin is especially noticeable on many fruits—e.g., apple, nectarine, and cherry, which can be buffed to a high gloss. 

Fats typically provide more than half of the body's energy needs. Fat from food is broken down into fatty acids, which can travel in the blood and be captured by hungry cells. Fatty acids that aren't needed right away are packaged in bundles called triglycerides and stored in fat cells, which have unlimited capacity. Fat is the body's most concentrated source of energy, providing more than twice as much potential energy as carbohydrate or protein (9 calories per gram versus 4 calories each per gram).

Receptor is a molecule usually found on the surface of a cell, that receives chemical signals from outside the cell. When such external substances bind to a receptor, they direct the cell to do something, such as divide, die, or allow specific substances to enter or exit the cell.

Receptors are proteins embedded in either the cell's plasma membrane (cell surface receptors), in the cytoplasm, or in the cell's nucleus (nuclear receptors), to which specific signaling molecules may attach.

• The prostaglandins are a group of physiologically active lipid compounds called eicosanoids having diverse hormone-like effects in animals.
• Prostaglandins have been found in almost every tissue in humans and other animals. 
• They are derived enzymatically from the fatty acid arachidonic acid. Every prostaglandin contains 20 carbon atoms, including a 5-carbon ring. 
• They are a subclass of eicosanoids and of the prostanoid class of fatty acid derivatives. Hence, Prostaglandins are complex fatty acids that function as intercellular messengers.

Carbohydrates are made up of C: H: O, having H and O in the ratio of 2:1 and the general formula is (CH2O)n. Sources of carbohydrates in our food are cereals and pulses. The caloric value is 4.1 kcal/g.

C_nH_2nO_n is a general formula of monosaccharides. Monosaccharides are the simplest carbohydrates which cannot be hydrolyzed into smaller units. They usually have 3-7 carbon atoms per molecule. They are the compounds of carbon, hydrogen, and oxygen in which hydrogen and oxygen occur in the ratio of 2:1 as in a molecule of water. Thus, they are also known as hydrates of carbon. 

Inulin is a storage polysaccharide in roots of Dahlia and related plants. It is also known as a fructan. It is not metabolized in the human body and is readily filtered through the kidney. Therefore, it is used in testing kidney function. Thus, the correct answer is B.

Chitin carbohydrates are the oldest in the given as it is a carbon-based factor. protein, lipids consist chain of nitrogen, hydrogen and carbon atoms however carbohydrate consists of a longer chain of carbon as well as various other groups of compounds. so, the correct option is 'chitin carbohydrates'.

Glucose is a monosaccharide carbohydrate. Glycogen is an important storage polysaccharide in animals like starch in plants. Glycogen and starch are homopolysaccharides made up of glucose units only. Glycogen is stored in liver and muscles in animals including humans. Starch is usually stored in endosperm and cotyledons of seeds. Waxes are a type of lipids.

Inulin is a group of naturally occurring polysaccharides produced by many types of plants, consisting of a chain of fructose units.

Chitin is a carbohydrate. It is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world. It is a characteristic component of the cell walls of fungi, the exoskeletons of arthropods such as crustaceans (e.g., crabs, lobsters and shrimps) and insects, the radulae of molluscs and the beaks and internal shells of cephalopods, including squid and octopuses. The structure of chitin is comparable to the polysaccharide cellulose, forming crystalline nanofibrils or whiskers. 

In animals fats, carbohydrates and proteins are responsible for generation of energy.
Proteins are metabolized by breaking down into individual amino acids by various enzymes and hydrochloric acid present in the gastro-intestinal tract which are further broken down to α-keto acids which can be recycled in the body for generation of energy, and production of glucose or fat or other amino acids.
Fats are the major contributor of the molicules like acetyl-CoA which is an integral part of Krebs cycle and generates energy.
Carbohydrates takes part in cellular process like glycolysis and leads to generation of energy.
Vitamins are not directly involved in generation of energy although they indirectly support the process of energy production.
So, the correct answer is option C.

A primary metabolite is a type of metabolite, which is directly involved in the normal growth, development, reproduction of an organism. e.g. Cellulose, cholesterol, triglycerides. Secondary metabolites which are not directly involved in the growth, development.  Secondary metabolite performs another function like defence. e.g. lecithin present in WBC which help in the recognition of foreign pathogen.