Fatty Acids – Precursors for Energy in Hibernation

Fatty acids can play a key role in hibernation. Hibernation is more than sleeping through the long, cold winter season. It is time for collection of food and conservation of energy for up to 6 months. For most mammals, it is a state of dormancy or inactivity where the conservation of energy is the priority in order to survive the harsh winter conditions. But the process of converting fats to energy is more complex than it appears. These animals that hibernate consume foods high in fat content to later use these complex components, converting them to simple carbon based chains by the beta-oxidation cycle. Fatty acids are lipid, complex hydrocarboxylic chains, made up of usually 16 to 18 carbons. These lipids are classified as saturated or unsaturated carbon based chains. Examples of saturated fatty acids are palmitic acid, stearic acid, and lauric acid. These types of saturated components are found in salmon and tuna. Examples of unsaturated fatty acids, which contain double bonds, are palmitoleic acid, oleic acid, and linoleic acid. Foods such as corn oil, sunflower oil, and soybeans are some examples that carry these types of components. In the cycle of oxidation of saturated fatty acids, these complex components are tagged with the energy currency ATP (adenosine triphosphate) to be carried from the cytosol to the mitochondrion in the cell. In the phospholipid rich membrane of the mitochondrion, the now called fatty acyl CoA or fatty acyl coenzyme A participates in the beta-oxidation process. The carbon based fatty acid chains are broken down into simpler fatty acyl-coA, reduced by 2 carbons, and an acetyl-coA. The breakdown of these molecules in the beta-oxidation cycle is considered to be a very energy rich process. In this exergonic pathway, three energy molecules are produced: NADH (nicotinamide adenine dinucleotide reduced form), FADH2 (flavin adenine dinucleotide reduced form), and acetyl-coA. Within the 4-step reaction pathway, specific enzymes catalyze these biochemical reactions. These functional enzymes are dehydrogenase, hydratase, and thiolase.

Once this process is in full motion, bears in particular are capable to endure harsh cold temperatures in dens or caves for long periods of times. As the temperature reaches freezing conditions, the metabolic pathways in bears are able to sustain the drastic changes in temperatures. In particular, their heart rate and metabolic changes are reduced below normal rates. While in hibernation, bears do not eat or pass off wastes. Bodily wastes are reused within the metabolic pathways of bears. It is still unclear how this biological phenomenon occurs in bears. In order for bears to subsist harsh sudden temperature changes, hibernation is an important part of survival. Fatty acid breakdown has helped in the process of hibernation.

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