The Study of Metabolism: Biological Thermodynamics

The three Laws of Thermodynamics govern the universe and everything it contains. These three laws are fundamental to our understanding of the universe, and in this particular case they help us to understand the various biological processes.

The First Law states that the total energy of the universe is always constant. Energy could neither be created nor destroyed, it could only be transformed. This is also known as the Law of conservation of energy.

The Second Law states that in any open system the total entropy always increases, in simpler terms the universe is always becoming more chaotic, disorderly.

The Third Law states that at all motion stops at when temperature reaches absolute zero, the entropy would also be zero.

When understanding metabolisms only the first two laws are of interest to us.

 Every metabolic process whether it is hunting for food, cellular respiration, or reproducing offspring requires energy. Since energy could not be created at will according to the First Law, organisms must obtain energy from somewhere. Plants take light energy from the sun and transform it into chemical energy in the form of carbohydrates. Animals take the chemical energy stored in plant and transform it into kinetic energy and heat. The First Law of Thermodynamics explains why I need to eat in order to do anything, but why do I need energy when I am not moving, not thinking, not digesting? This is where the Second Law of Thermodynamics comes in. Every spontaneous event always increases the entropy of the system, which means the entropy level in our body always increases just by existing in the universe. This means our body gets more disorganized, our cells breakdown, and we age. Our body is like a china plate, and time, which could be understood as increase in entropy is like a hammer that breaks the plate. The plate shatters into many pieces as it follows the Second Law of Thermodynamics. We try to glue the pieces back together but no matter how hard we try the plate would not return to its unbroken state. As time goes on and the plate is shattered again and again, it will eventually reach a state beyond repair. Our body is constantly undergoing wear and tear and it is constantly being repaired which of course requires energy and nutrient. Just like the china plate our body will reach its limit one day and then we die. Just as a side note this is also the reason why our universe will end in 500 billion years. But what can you do, it is the way of the universe.

Facts about carbohydrates

-Carbohydrates are simply chemicals compounds composed of carbon, hydrogen, and oxygen

-The formula for carbohydrates follows a ratio of 1 carbon:2 hydrogen:1 oxygen

-Carbohydrates are the primary source of energy for our body and makes up the majority of our diet

-There are three groups of carbohydrates, or saccharides as referred to in biochemistry: monosaccharide, polysaccharide, and oligosaccharide

Monosaccharide

-Monosaccharaides are the simplest of all the carbohydrates, these simple sugars are either aldehydes or ketones with hydroxyl groups; i.e. glucose and fructose

-These simple sugar are the building block for more complex carbohydrates and essential building blocks for nucleic acids

-The monosaccharaides are separated by the number of carbon molecules; a monosaccharide with 5 carbons is called a pentose, and hexose with 6 carbons

Oligosaccharide and Polysaccharide

-The simple sugars could join together to form more complex carbohydrates through the formation of glycosidic bonds

-Condensation is the process of forming glycosidic bonds, in which the hydroxyl group of two sugars join together and splitting out water molecule as by-product

-Hydrolysis is the process in which a complex sugar reacts with water to produce two or more simpler sugars

-Oligosaccharides are carbohydrates formed when a few sugars are joined together, typically between two to ten

-Sucrose is a disaccharide formed by a glucose molecule and a fructose molecule, it is commonly known as table sugar

-Oligosaccharides has many function, including forming glycoproteins and glycolipids

-Oligosaccharides play important role in cell-to-cell recognition

 -Polysaccharides are carbohydrate chains of lots of simple sugars

-Polysaccharides could be linear in shape (i.e. amylose) or branched (i.e. glycogen)

-Polysaccharides act as energy storage units in organisms and provide structural support

-Amylose is a linear glucose polymer found in plants as energy storage; because it is linear it is harder to digest and takes up less space

-Glycogen is a branched glucose polymer found in animals, its structure provides rapid release of glucose which is then transformed into energy

-Cellulose is another linear glucose polymer found in plants, it is the main material for cell walls, and it is very hard to digest in our body and is the major source of our dietary fibre