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 determaine the
form of fat ?
answer :
because fats is saturated than oil is
unsaturated. 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.
A fat's constituent fatty acids may also
differ in the C/H ratio. When all three fatty acids have the formula CnH(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 CnH(2n-1)CO2H. These fatty acids
contain double bonds within carbon chain. This results in an
"unsaturated" fatty acid. More specifically, it would be a
monounsaturated fatty acid. Polyunsaturated fatty acids would be fatty acids
with more than one double bond; they have the formula, CnH(2n-3)CO2H and
CnH(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.
Saturated
fatty acids have higher melting points than unsaturated fatty acids,Saturated fatty acids adopt a fully extended
conformation, pack well, and have strong van der Waals attractions between
molecules.
Cis double
bonds in unsaturated fatty acids put bends in the chainUnsaturated fatty acid
chains pack poorly and have weaker van der Waals attractions between molecules
than saturated fatty acids Unsaturated fatty acids have lower melting points than saturated fatty
acids with the same number of carbons
Triacylglycerols
with a higher content of saturated fatty acids have higher melting points,Triacylglycerols in animal fats contain mostly
saturated fatty acids and are solids are room temperature,Triacylglycerols in oils have a large
proportion of unsaturated and polyunsaturated fatty acids and are therefore
liquids are room temperature.
2.
how a
primary metabolite can be converted into secondary metabolites . what is the
basic idea and how the mechanism could be described ?
answer
:
the basic ide is The building blocks for secondary metabolites are derived from primary metabolism. The number of building blocks needed
is surprisingly few. The most important
building blocks employed in the biosynthesis of secondary metabolites are
derived from:
- Acetyl coenzyme A (acetyl-CoA)
- Shikimic acid
- Mevalonic acid
- 1-deoxyxylulose 5-phosphate
- Amino acids
3. BIOSYNTHESIS
PROGESTERONE
progesterone like all other steroid hormones, is synthesized
from pregnenolone , which in turn is derived from cholesterol.
This is step reactions to formation progesterone
- Cholesterol undergoes double oxidation to produce 20,22-dihydroxycholesterol.
- This vicinal diol is then further oxidized with loss of the side chain starting at position C-22 to produce pregnenolone. This reaction is catalyzed by cytochrome P450scc.
- The conversion of pregnenolone to progesterone takes place in two steps.
- First, the 3-hydroxyl group is oxidized to a keto group
- second, the double bond is moved to C-4, from C-5 through a keto/enol tautomerization reaction. This reaction is catalyzed by 3beta-hydroxysteroid dehydrogenase/delta(5)-delta(4)isomerase.
Progesterone in turn is the precursor of the mineralocorticoid aldosterone, and after conversion
to 17-hydroxyprogesterone (another natural progestogen) of cortisol and androstenedione. Androstenedione can be
converted totestosterone, estrone and estradiol.
The recent development of practical methods for the asymmetric preparation of amines has enabled creative approaches to alkaloid construction. Günter Helmchen of the Ruprecht-Karls-Universität Heidelberg developed (Synlett 2009, 1413. DOI: 10.1055/s-0029-1217165) an iridium catalyst that mediated the enantioselective amination of the allylic carbonate 1 to give 2. Hydroformylation followed by reduction then completed the synthesis of (S)-nicotine (3).
4.
