Ahmed

North Carolina State University

Transport of Fatty Acids in a Body

Hamza Ahmed

Ans 230-001

Dr. Sung Woo Kim

April 1st, 2016

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Transport of Fatty Acids in a Body

Fatty acids are common in animal cells and are necessary for good health.

Omega-3 and Omega-6 are essential fatty acids commonly added to food for health

benefits. Furthermore, fatty acids are used in the body to make lipoproteins and also new

cells. Some examples where fatty acids can be found are in the phospholipid bilayer and

intercellular messengers. Fatty acids are excellent at being stored as reserve energy for

cells and yield the most ATP out of all macromolecules. Being said, fatty acids are

important for the physiological processes in the body. They can be broken down and used

as an energy source when glucose is not available. Glucose is the body’s main source of

energy and easily metabolized. A major source of fatty acids in a body is from dietary

means in the form of triglycerides. Therefore the transportation of fatty acids is crucial in

the body. The transportation of fatty acids first begins with digestion. Since most fatty

acids entering the body are in the form of triglycerides, they must be broken down first.

The body has many ways of breaking down fats/triglycerides to fatty acids where they

can be absorbed into the blood stream. There are enzymes in the mouth, stomach and

pancreas that breakdown fats. Also, organs like the small intestine play a very important

role in digestion of fat. In addition, they are processes like beta-oxidation and lipolysis

that occur in the body when needed. The breakdown and absorption of fats to fatty acids

is the way fatty acids can be transported to different tissues in the body where they are

needed. This allows the body to use these fatty acids for cell development, energy and

energy storage.

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Most fatty acids in the body enter from ones diet. This is why the nutrition of an

individual is very important because it ensures there is sufficient amount of fatty acids in

the body. Especially for a class of essential fatty acids called Omega-3 and Omega-6 fatty

acids. They are called essential fatty acids because the body cannot produce them

naturally. Essential fatty acids like Omega-3 have positive health benefits for the

developing brain. Docosahexaenoic acid also known as DHA, is found in Omega-3 and

contains 22 carbons and 6 double bonds (Innis, 2008). DHA helps the growth and

function of the developing nervous tissue in the body (Innis, 2008). Furthermore, the lack

of Docosahexaenoic acid (DHA) can lead to problems in neurogenesis, visual function

and learning (Innis, 2008). Arachidonic acid, which is found in Omega-6, also has the

same positive health benefits for the brain. Fatty acids must pass the blood brain barrier

that protects the brain by protein-mediated transport or diffusion (Mitchell et al., 2011).

The blood brain barrier protects the brain by denying passage of certain substances

(Mitchell et al, 2011). Therefore the nutrition of the mother is important for providing

essential fatty acids to the developing fetus. Innis mentions that malnutrition can also lead

to short and long term issues with infant neural function (Innis, 2008). The blood of

premature babies shows low levels of Docosahexaenoic Acid, which has been correlated

with eye dysfunction and permanent brain issue damage (Duttaroy, 2008). The brain and

retina both are abundant in long chain polyunsaturated fatty acids, arachidonic fatty acids

and docosahexaenoic acid, which is why these essential fatty acids support development.

The placenta is the organ that allows the nutrients from the mother to be passed to the

fetus (Duttaroy, 2008). Without the placenta, the transportation of fatty acids from

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mother to fetus would be difficult. In addition, the metabolism, which ultimately leads to

the transportation of the fatty acids, is crucial (Duttaroy, 2008).

The transportation of dietary fatty acids begins with metabolizing fat. Lingual

lipase, which is located in the mouth, is the first enzyme to start breaking down the fat

(Joyce, 1998). It is important to note most dietary fatty acids come in the form of

triglycerides. Once the food reaches the stomach another enzyme known as gastric lipase

starts working. Both these enzymes are insignificant in the process of metabolization of

fat. The stomach is beneficial in digestion of fat because it helps emulsify the fat, which

helps in the breakdown of the fat (Fats and Oils in Human Nutrition, 1994). It is not until

the fat reaches the small intestine where most of the fat is metabolized and absorbed.

Since fat is generally insoluble, bile salt helps make the content more water-soluble. The

duodenum also helps by mechanically emulsifying the fat. Micelles are formed from the

insoluble fatty acids in the small intestine. In the small intestine, pancreatic lipase, which

is released by the pancreas, helps to split triglycerides into fatty acids (Joyce, 1998).

Enterocytes located in the walls of the intestines absorb the free fatty acids released by

the breakdown of the fat from enzymes and emulsification processes. The fatty acids that

have a carbon chain with more than 14 carbons are turned into chylomicrons and

circulated via the blood stream (Fats and Oils in Human Nutrition, 1994). Chylomicrons

are lipoproteins that are packaged by mucosa cells. They can either be transported to

adipocytes and be stored for energy or can be sent to muscle cells where they will be used

as fuel. If one were to exercise right after a meal, the fat would be sent to the muscle cells

instead of adipocytes. Fatty acids with carbon chains with less than 14 carbons are

transported to the liver through the portal vein (Fats and Oils in Human Nutrition, 1994).

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The liver also plays a role in digesting fatty acids. Once the liver is full with glycogen, it

will start converting glucose from the blood to fatty acids which can then again be put in

the blood stream and sent to the cells that need it.

The transportation of fatty acids across a cell membrane can be done by a few

different ways. The first way involves with fatty acids that pass through the cell

membrane by a protein-mediated mechanism (Schwenk et al., 2010). These carrier

proteins not only transport fatty acids but also act as a mediator for the uptake of fatty

acids in the cell. The efficiency of uptake of fatty acids is an important cellular function

(Schaffer, 2002). Since fatty acids are amphipathic it helps the fatty acids to move across

the cellular membrane (Hamilton, 1998). This is because the membrane of an animal cell

is composed of a phosolipid bi-layer, which has a polar head, and non-polar tails which is

similar to the composition of fatty acids. Essentially the similarities in the biophysical

properties allow the easy access through the membrane (Schwenk et al., 2010).

Fatty acids can also be used as an energy source. A catabolic process known as

beta-oxidation occurs when protein and carbohydrates are not present to provide energy.

Also fat takes longer to break down and metabolize compared to other macromolecules.

In beta-oxidation, fatty acids are broken down in the mitochondria. Beta-oxidation can

also occur in peroxisomes when the carbon chain of the fatty acid is too long for the

mitochondria (Reddy et al., 2001). Before they are broken down, they are activated for

degradation by coenzyme A, which forms acyl-CoA thioester. In the heart, the cardiac

cells require a greater need for energy and beta-oxidation of long chain fatty acids help

sustain that energy requirement (Lopaschuk et al., 2010). These preliminary steps are

ultimately the reason why it takes longer for fat to break down and also because they are

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insoluble in water. It would not be efficient for the body to use fat as a primary source of

energy. So it is logical to understand why fatty acids are used as an energy source when a

more immediate energy source is not available.

In conclusion, fatty acids play many important physiological roles. They are

present in various structures in the body like the phospholipid bi-layer and lipoproteins.

Essential fatty acids found in Omega-3 and Omega-6 play an important role in the

development of the brain and neurons. Lacking essential fatty acids in pregnant woman

can affect the fetus neural development. Since the body cannot make these essential fatty

acids, it is ultimately up to the individual to have a good diet. Many food producers have

put Omega-3 in their products, which can be easily found in most food markets today.

Fatty acid transport begins with enzymes breaking down fats and triglycerides to fatty

acids. Enzymes like lingual, gastric and pancreatic lipase are the ones involved. In

addition, the small intestine is the major organ for fat digestion. The digestion and

metabolizing of fat to fatty acids help the body absorb the fatty acids and put it in the

blood stream and then transported and reassembled for a specific purpose. Fatty acids can

be used as fuel by muscle cells if carbohydrates are not present and can also be stored

until a later point when energy is needed. Fatty acids can pass through the cell membrane

by either diffusion or protein-mediated transportation. Since the cell membrane

composition is similar to fatty acids, it easily passes through the membrane. Processes

like beta-oxidation help turn fatty acids into usable energy and help support the energy

demand of cardiac muscles. Energy is the body’s currency for its mechanisms. Thus,

maintenance of appropriate fatty acids is essential to proper body function.

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Literature Cited

Diwan, Joyce J.1998. "Lipoproteins." Lipoproteins. Chime, n.d.

Duttaroy, A. "Transport of Fatty Acids across the Human Placenta: A Review."Progress in Lipid Research 48.1 (2009): 52-61. Web.

Fats and Oils in Human Nutrition: Report of a Joint Expert Consultation, Rome, 19-26 October 1993. Rome: World Health Organization, 1994. Print.

Hamilton, James A.1998. "Fatty Acid Transport:difficult or Easy?" Journal of Lipid Research (n.d.): n. pag.

Innis, Sheila M .2008. "Dietary Omega 3 Fatty Acids and the Developing Brain."Brain Research 1237: 35-43.

Lopaschuk, Gary D., John R. Ussher, Clifford D.L Folmes, Jagdip S. Jaswal, and William C. Stanley. 2010. "Myocardial Fatty Acid Metabolism in Health and Disease." American Physiological Society : n. pag.

Mitchell, Ryan W., Ngoc H. On, Marc R. Del Bigio, Donald W. Miller, and Grant M. Hatch. 2011. "Fatty Acid Transport Protein Expression in Human Brain and Potential Role in Fatty Acid Transport across Human Brain Microvessel Endothelial Cells." Journal of Neurochemistry : n. pag.

Reddy, Janardan K., and Takashi Hashimoto. 2001. "Peroxisomal Beta-oxidation and Peroxisome Proliferator--activated Receptor Alpha: An Adaptive Metabolic System." Annual Review of Nutrition (n.d.): n. pag.

Schaffer, Jean E.2002 "Fatty Acid Transport: The Roads Taken: Fig. 1." American Journal of Physiology - Endocrinology And Metabolism Am J Physiol Endocrinol Metab 282.2 n. pag.

Schwenk, Robert W., Graham P. Holloway, Joost J.f.p. Luiken, Arend Bonen, and Jan F.c. Glatz. 2010."Fatty Acid Transport across the Cell Membrane: Regulation by Fatty Acid Transporters." Prostaglandins, Leukotrienes and Essential Fatty Acids (PLEFA) 82.4-6 149-54.

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