LEGO BRICKS OF LIFE
BBS1001
, Case 01
STRUCTURE OF FATS
A fat is the product of fatty acids bonded to a
backbone structure, which is often a glycerol
which consists of a 3-carbon chain. Fatty acids
consist of the elements carbon (C), hydrogen
(H) and oxygen (O) arranged as a carbon chain
skeleton with a carboxyl group (-COOH) at one
end. A triglyceride is a specific type of fat
formed by the combination of 3 fatty acids with
a glycerol backbone. A fatty acid is unsaturated
if there is at least one double bond between
the carbon atoms in the fatty acid. A fatty acid
with only one double bond is called a monounsaturated fatty acid. A fatty acid with two or more
double bonds is called a polyunsaturated fatty acid. A fatty acid with no double bonds between the
carbon atoms in the main carbon chain of the fatty acid is called saturated fatty acid. The term
“omega” refers to the position of double bond in relation to methyl group on the end of the fatty
acid. As an example, omega-3 (ω-3) fatty acids have the last double bond 3 carbons from the
terminal methyl group. Chylomicrons are lipoprotein particles that consist of triglycerides (85–
92%), phospholipids (6–12%), cholesterol (1–3%), and proteins (1–2%). They transport
dietary lipids from the intestines to other locations in the body.
STRUCTURE OF SUGARS
Scientifically, sugar loosely refers to a number of carbohydrates, such
as monosaccharides and disaccharides. Monosaccharides are also
called "simple sugars," the most important being glucose. Most
monosaccharides have a formula that conforms to CnH2nOn with n
between 3 and 7 (deoxyribose being an exception). Glucose has
the molecular formula C6H12O6. The names of typical sugars end with
-ose, as in "glucose" and "fructose". Sometimes such words may also
refer to any types of carbohydrates soluble in water. The acyclic mono-
and disaccharides contain either aldehyde groups or ketone groups.
These carbon-oxygen double bonds (C=O) are the reactive centers. All
saccharides with more than one ring in their structure result from two
or more monosaccharides joined by glycosidic bonds with the resultant loss of a molecule of water
(H2O) per bond.
FAT DEGRADATION
Lipolysis is the breakdown of lipids and it involves hydrolysis of triglycerides into glycerol and 3 fatty
acids. This happens in the cytoplasm. So first, the hormones adrenalin, catecholamine and cortisol
glucagon activate adenylyl cyclase. This enzyme catalyzes the process of ATP to c-AMP. This last
molecule activates lipase (HSL), which catalyzes the process of triacylglycerol (TAG) to glycerol and
fatty acids. After this happened these products can be used by the cells in our blood. Insulin blocks this
1
,last process. So, no glycerol or fatty acids can be used by the cells. Fatty acids are molecules which act
as fuel molecules. They are also building blocks of phospholipids and glycolipids.
There are different types of fatty acid oxidation:
1) Beta oxidation: major mechanism, occurs in the mitochondria. 2 carbon-units are released as
acetyl CoA per cycle. This is the major source (80%!) of energy for the heart.
2) Alpha oxidation: predominantly takes place in brain and liver. 1 carbon is lost in the form of CO2
per cycle. It is not an energetic process.
3) Omega oxidation: minor mechanism, but it becomes important in conditions of impaired beta
oxidation.
4) Peroxisomal oxidation: mainly for the trimming of a very long chain fatty acids.
BETA OXIDATION
DIFFERENCE BETWEEN NATURAL AND SYNTHETIC FATS
Trans fats are a type of unsaturated fat that occur in small amounts in nature, but it is widely produced
industrially from vegetable fats for use in margarine, snacks and baked goods. Trans fat has been
shown to consistently be associated with increased risk of coronary artery disease. The chain of a trans-
fat is more inflexible, which is more difficult for the body to handle. In addition, it raises the levels of
LDL (‘bad cholesterol’) and lowers the levels of HDL (‘good cholesterol’) and it increases the risk of
diseases. LDL (Low-Density Lipoprotein) particles are sometimes referred to as bad cholesterol because
they can transport their content of lipid molecules into artery walls, attract macrophages, and thus
drive atherosclerosis. In contrast, HDL (High-Density Lipoprotein) particles are often called good
cholesterol or healthy cholesterol because they can remove lipid molecules from macrophages in the
wall of arteries. Fats contain long hydrocarbon chains, which can either be unsaturated (with double
bonds) or saturated (without double bonds). Partial hydrogenation of the unsaturated fat converts
some of the cis double bonds into trans double bonds. Hydrogenation is the process used to convert
oil into solid trans fats by adding hydrogen, the number of double bonds will be decreased too. This
process occurs in nature too. Bacteria in animals' stomachs hydrogenate the fatty oils from animal
feed, for example. But natural trans fats are less harmful than the artificial ones, because food factories
hydrogenate it partially.
2
, ESSENTIAL AND NON-ESSENTIAL FATS
All fats, including saturated fatty acids, have important roles in the body. However, the most important
fats are those that the body cannot make and thus must come from the food we eat. These essential
fatty acids (EFAs) are based on linoleic acid (omega-6 group) and alpha-linolenic acid (omega-3 group).
We need both groups of essential fatty acids to survive. Along with omega-3 fatty acids, omega-6 fatty
acids play a crucial role in brain function, and normal growth and development. As a type of
polyunsaturated fatty acid (PUFA), omega-6s help stimulate skin and hair growth, maintain bone
health, regulate metabolism, and maintain the reproductive system. A healthy diet contains a balance
of omega-3 and omega-6 fatty acids. Omega-3 fatty acids help reduce inflammation, and some omega-
6 fatty acids tend to promote inflammation. So, the ratio is very important. Non-essential fatty acids
are acids that the body itself can synthesize. We don’t need to get these fatty acids through our food.
Example of non-essential fatty acids are palmitic acid and stearic acid.
SUGAR DEGRADATION
The glycemic index is a value assigned to foods based on how slowly or how quickly those foods cause
increases in blood glucose levels. Also known as "blood sugar," blood glucose levels above normal are
toxic and can cause blindness, kidney failure, or increase cardiovascular risk. Foods low on the glycemic
index (GI) scale tend to release glucose slowly and steadily. Foods high on the glycemic index release
glucose rapidly. Low GI foods tend to foster weight loss, while foods high on the GI scale help with
energy recovery after exercise. When you eat (for instance) a sandwich, amylase will break the starch
that is in your sandwich partially to shorter polysaccharides and oligosaccharides. It digests it partially,
because it is inactivated when it arrives the stomach. The acidic environment is responsible for that.
The stomach will only mix the content around and allow it to reach the small intestine. That’s where
most processes happen. Within the lumen of the small intestine we see cells. These cells are known as
enterocytes. These contain brush boarder enzymes. These enzymes play a role in the digestion of
starch. These enzymes include maltase, which hydrolyses maltose to glucose. So, at the end of the
starch digestion, you will have the building blocks of starch, which is glucose. Glucose can be used in
the blood stream as energy or it will be stored in the liver in the form of glycogen.
WHY DO WE NEED FATS AND SUGARS ?
Cells require a constant supply of energy to generate and maintain the biological order that keeps
them alive. They get this energy from food molecules, these serve as fuel for cells. Sugars, but also fats,
are important fuel molecules. They are oxidized in small steps to carbon dioxide (CO2) and water
(H2O). The energy that comes free is useful, but if the sugar is oxidized in just one step, the amount of
energy would be much more.
This energy is however useless, it is much more than it could
be captured for useful purposes. Instead this energy will be
released as heat. This process of degrading complex molecules
to simple ones is called catabolism. These reactions are
enzyme-catalyzed and release energy. Metabolism is the
process where it converses food/fuel into energy or building
blocks. Glucose dominates the energy production in most
animal cells. Other molecules, such as fatty acids and proteins,
can also serve as an energy source when they are funneled
through appropriate enzymatic pathways. Fat serves as a highly-concentrated form of energy and it is
the primary way our body stores energy for the long term. Sugars provide quick energy to our body.
The proteins, lipids, and polysaccharides that make up most of the food we eat must be broken down
3
