Examination natural product chemistry

1.      Fats generally are solid while the oil is liquid phase, however both are equally triglyceride. Explain why the form of two different triglyceride, and point out important factors that determine the form of fat?

Answer:          

A fat's constituent fatty acids may also differ in the C/H ratio. When all three fatty acids have the formula C_nH_(2n+1)CO₂H, the resulting fat is called "saturated". Values of n usually range from 13 to 17. Each carbon atom in the chain is saturated with hydrogen, meaning they are bonded to as many hydrogens as possible. Unsaturated fats are derived from fatty acids with the formula C_nH_(2n-1)CO₂H. These fatty acids contain double bonds within carbon chain. This results in an "unsaturated" fatty acid. More specifically, it would be amonounsaturated fatty acid. Polyunsaturated fatty acids would be fatty acids with more than one double bond; they have the formula, C_nH_(2n-3)CO₂H and C_nH_(2n-5)CO₂H. Unsaturated fats can be converted to saturated ones by the process of hydrogenation. This technology underpinned the development of margerine.

Saturated and unsaturated fats differ in their energy content and melting point. Since unsaturated fats contain fewer carbon-hydrogen bonds than saturated fats with the same number of carbon atoms, unsaturated fats will yield slightly less energy during metabolism than saturated fats with the same number of carbon atoms. Saturated fats can stack themselves in a closely packed arrangement, so they can freeze easily and are typically solid at room temperature. For example, animal fats tallow and lard are high in saturated fatty acid content and are solids. Olive and linseed oils on the other hand are highly unsaturated and are oily.

There are many different kinds of fats, but each is a variation on the same chemical structure. All fats are derivatives of fatty acids and glycerol. The molecules are called triglycerides, which are triesters of glycerol (an ester being the molecule formed from the reaction of the carboxylic acid and an organic alcohol). As a simple visual illustration, if the kinks and angles of these chains were straightened out, the molecule would have the shape of a capital letter E. The fatty acids would each be a horizontal line; the glycerol "backbone" would be the vertical line that joins the horizontal lines. Fats therefore have "ester" bonds.

The properties of any specific fat molecule depend on the particular fatty acids that constitute it. Different fatty acids are composed of different numbers of carbon and hydrogen atoms. The carbon atoms, each bonded to two neighboring carbon atoms, form a zigzagging chain; the more carbon atoms there are in any fatty acid, the longer its chain will be. Fatty acids with long chains are more susceptible to intermolecular forces of attraction (in this case, van der Waals forces), raising its melting point. Long chains also yield more energy per molecule when metabolized.

            Triglycerides in the fat oil

Can be either solid or liquid depending on the composition of the constituent fatty acids. Liquid  vegetable oil because it contains unsaturated fatty acids, while animal fats are generally solid at room temperature because it contains unsaturated fatty acids.

             Fat oil

Triglycerides are composed of a mixture of esters of glycerol and long chain fatty acids. Fat if the oil will produce three molecular hydrolyzed long-chain fatty acids and a glycerol molecule.

           Triglycerides oil fatty

Derived from various sources have physico-chemical properties are different from each other that occurs because of differences in the number and types of esters contained therein.

            Triglycerides in the fat oil

Did not differ in their chemical composition differing only in shape or form. Triglycerides are called oils when melted at room temperature and is called solid if it freezes at room temperature.

A triglyceride molecule

  

Types of fats in food
Unsaturated fat Monounsaturated fat Polyunsaturated fat Trans fat Cis fat Omega fatty acids: ω−3 ω−6 ω−9 Saturated fat Interesterified fat

2.   How a primary metabolite can be converted into secondary metabolites. What is the basic idea and how the mechanism could be described.

Answer:

Primary metabolite  can be converted into secondary metabolisme from the reaction the fundamental processes of photosynthesis, glycolysis, and the Krebs cycle are tapped off from energy-generating processes to provide biosynthetic intermediates.To make biosynthesis intermediets needs the buillding blocks. By far the most important building blocks employed in the biosynthesis of secondary metabolites are derived from the intermediates acetyl coenzyme A (acetyl-CoA), shikimic acid, mevalonic acid, and methylerythritol phosphate. These are utilized respectively in the acetate, shikimate, mevalonate, and methylerythritol phosphate pathways, Acetyl-CoA is formed by oxidative decarboxylation of the glycolytic pathway product pyruvic acid. It is also produced by the β-oxidation of fatty acids, effectively reversing the process by which fatty acids are themselves synthesized from acetyl-CoA. Important secondary metabolites formed from the acetate pathway include phenols, prostaglandins, and macrolide antibiotics, together with various fatty acids and derivatives at the primary–secondary metabolism interface. Shikimic acid is produced from a combination of phosphoenolpyruvate, a glycolytic pathway intermediate, and erythrose 4-phosphate from the pentose phosphate pathway. The reactions of the pentose phosphate cycle may be employed for the degradation of glucose, but they also feature in the synthesis of sugars by photosynthesis. The shikimate pathway leads to a variety of phenols, cinnamic acid derivatives, lignans, and alkaloids. Mevalonic acid is itself formed from three molecules of acetyl-CoA, but the mevalonate pathway channels acetate into a different series of compounds than does the acetate pathway. Methylerythritol phosphate arises from a combination of two glycolytic pathway intermediates, namely pyruvic acid and glyceraldehyde 3-phosphate by way of deoxyxylulose phosphate. The mevalonate and methylerythritol phosphate pathways are together responsible for the biosynthesis of a vast array of terpenoid and steroid metabolites.

In addition to acetyl-CoA, shikimic acid, mevalonic acid, and methylerythritol phosphate, other building blocks based on amino acids are frequently employed in natural product synthesis. Peptides, proteins, alkaloids, and many antibiotics are derived from amino acids, and the origins of some of the more important amino acid components of these are briefly indicated in Figure 2.1. Intermediates from the glycolytic pathway and the Krebs cycle are used in constructing many of them, but the aromatic amino acids phenylalanine, tyrosine, and tryptophan are themselves products from the shikimate pathway. Ornithine, an amino acid not found in proteins, and its homologue lysine, are important alkaloid precursors and have their origins in Krebs cycle intermediates. Of special significance is the appreciation that secondary metabolites can be synthesized by combining several building blocks of the same type, or by using a mixture of different building blocks. This expands structural diversity and, consequently, makes subdivisions based entirely on biosynthetic pathways rather more difficult. A typical natural product might be produced by combining elements from the acetate, shikimate, and methylerythritol phosphate pathways.

3. Hormone progesterone is essential for the survival of the pregnancy. These hormones are drived from a streoid biognetically. Explain the logic of chemical reactions which may occur in the formation of progesterone.

               answer :

                  In mammals, progesterone , like all other steroid hormones, is synthesized from pregnenolone , which in turn is derived fromcholesterol. Cholesterol undergoes double oxidation to produce 20,22-dihydroxycholesterol. This vicinaldiol is then further oxidized with loss of the side chain starting at position C-22 to produce pregnenolone . This reaction is catalyzed bycytochrome P450scc. The conversion of pregnenolone to progesterone takes place in two steps. First, the 3-hydroxyl group is oxidized to a keto group  and second, the double bond is moved to C-4, from C-5 through a keto/enoltautomerization reaction. This reaction is catalyzed by 3beta-hydroxysteroid dehydrogenase/delta(5)-delta(4)isomerase.

Progesterone in turn (see lower half of figure to the right) is the precursor of the mineralocorticoid aldosterone, and after conversion to 17-hydroxyprogesterone (another natural progestogen) of cortisol and androstenedione. Androstenedione can be converted to testosterone,estrone and estradiol.

Pregenolone and progesterone can also be synthesized by yeast.

The Marker semisynthesis of progesterone fromdiosgenin.

The Johnson total synthesis of progesterone.

4. Many alkaloids are toxic to other organism. They often have pharmacological effects and are used as medications, as recreational drugs, or in entheogenic rituals. Describe in outline the process of biosynthesis of an alkalois compound and describe the functions groups which play an important role in the biological activities.


answer : 

         Tyrosine (abbreviated as Tyr or Y) or 4-hydroxyphenylalanine, is one of the 22 amino acids that are used by cells to synthesize proteins. Its codons are UAC and UAU. It is anon-essential amino acid with a polar side group. The word "tyrosine" is from the Greek tyri, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese. It is called tyrosyl when referred to as a functional groupor side chain.Aside from being a proteinogenic amino acid, tyrosine has a special role by virtue of thephenol functionality. It occurs in proteins that are part of signal transduction processes. It functions as a receiver of phosphate groups that are transferred by way of protein kinases(so-called receptor tyrosine kinases). Phosphorylation of the hydroxyl group changes the activity of the target protein.

           A tyrosine residue also plays an important role in photosynthesis. In chloroplasts(photosystem II), it acts as an electron donor in the reduction of oxidized chlorophyll. In this process, it undergoes deprotonation of its phenolic OH-group. This radical is subsequently reduced in the photosystem II by the four core manganese clusters.

           Tyrosine is a precursor to neurotransmittersand increases plasma neurotransmitter levels (particularly dopamine and norepinephrine)but has little if any effect on mood. The effect on mood is more noticeable in humans subjected to stressful conditions (see below).

A number of studies have found tyrosine to be useful during conditions of stress, cold, fatigue, loss of a loved one such as in death or divorce, prolonged work and sleep deprivation, with reductions in stress hormone levels, reductions in stress-induced weight loss seen in animal trials, improvements in cognitive and physical performanceseen in human trials; however, because tyrosine hydroxylase is the rate-limiting enzyme, effects are less significant than those of l-dopa.

Tyrosine does not seem to have any significant effect on mood, cognitive or physical performance in normal circumstances. A daily dosage for a clinical test supported in the literature is about 100 mg/kg for an adult, which amounts to about 6.8 grams at 150 lbs. The usual dosage amounts to 500–1500 mg per day (dose suggested by most manufacturers; usually an equivalent to 1–3 capsules of pure tyrosine). It is not recommended to exceed 12000 mg (12 g) per day. In fact, too high doses result in reduced levels of dopamine. Tyrosine may decrease the absorption of other amino acids in high or chronic doses. It decreases absorption of l-dopa.

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