Metabolism and the Law of Thermodynamics.

DEFINITIONS:

Catabolic Reactions: reactions that result in the breakdown of complex substances.
Anabolic Reactions: cells build complex substances from simpler subunits e.g: DNA from nucleotidessum of all anabolic and catabolic processes in a cell or organism
Metabolism: sum of all anabolic and catabolic processes in a cell or organism

First Law of Thermodynamics/Law of Conservation Energy: states that energy can neither be created nor destroyed. It may change from one form to another, but the energy in a closed system remains constant.

Second Law of Thermodynamics/Law of Entropy: states that when energy is transferred, there will be less energy available at the end of the transfer process than at the beginning. Due to entropy, which is the measure of disorder in a closed system, all of the available energy will not be useful to the organism. Entropy increases as energy is transferred.

Third Law of Thermodynamics/Absolute Zero: theoretical temperature (0K) at which entropy reaches its minimum value.

CONNECTIONS:

 It is important to keep in mind that the human body does not consume energy, it merely changes it from one form to another, in reference to the first law, where it can be concluded that energy is conserved. The Law of Entropy states that a highly ordered system, such as life, tends to become more and more disordered. The increase in entropy in the surroundings produced by the living system is always greater than the decrease in entropy obtained in the living system itself. For example, if one were to drop mass, its potential energy is transformed into kinetic energy, and then into heat, sound and light. As a result, the entropy of the surroundings (the universe) will increase. The change in entropy is a function of the energy transformed in the body. In other words, an exergonic reaction releases energy which would increase entropy while endergonic reactions would decrease entropy. Looking at it from a 'big picture' perspective, where the planet is considered a closed system, the entropy will always be increasing. Additionally, if the world reached a temperature of absolute zero, humans would cease to exist for all the bonds would be broken. Humans are nothing but bonds being held together... therefore, is there really a point in referring the third law to metabolism? If I must, it would be the point where all molecular motions would cease and the high temperature would render the enzyme useless, for they would not be able to function. Ultimately, this is how I think metabolism obeys the three Laws of Thermodynamics.

Carbohydrates - twenty points to keep in mind.

1. among the most common organic material on Earth

2. used by organisms as sources of energy, as building materials, and as cell surface markers for cell-to-cell identification and communication

3. composed of carbon, hydrogen and oxygen in a 1:2:1 ratio

4. emperical formula:

where n represents the number of carbon atoms

5. the simplest carbohydrates are monosaccharides which contain a single chain of carbon atoms which hydroxyl groups are attatched, additionally the two simplest forms of monosaccharides are dihydroxyacetone and glyceraldehyde.

6. monosaccharides can be distinguished by the carbonyl group they possess, whether it be aldehyde of ketone, as well as the number of atoms in their carbon backbone

7. sugar with three carbons is called a triose, four carbons - tetrose, five carbons - pentose and six carbons - hexose

8. when two monosaccharides come together, it is called a disaccharide

9. when a few of the disaccharides form a covalent bond, it is called oligosaccharides

10. polymers consisting of chains of monosaccharide of disaccharide units are called polysaccharides

11. due to the tetrahedral nature of carbon bonds, and depending on the sugar, pyranose sugars form a 'chair' or 'boat' configuration

12. glycosidic bonds forms when the anomeric hydroxyl and a hydroxly of another sugar or some other compound that can join together which results in the splitting water and ultimately forming the glycosidic bond

13. plants store glucose as amylose of amylopectin, glucose polymers collectively called 'starch'

14. glucose storage in polymeric form minimizes osmotic effects

15. amylose if a glucose polymer withlinkages and adopts a helical conformation

16. the 'twin sister' named amylopectin is uglier, with a glucose polymer mainly  linkages, but it also has branches formed by linkages

17. amylopectin has a friend named glycogen with a similar structure with more  branches where the highly branched structure permits rapid release of glucose from glycogen stores

18. cellulose is a major component of plant cell walls for strength and rigidity, and it consists of long linear chains of glucose with  linkages

19. lectins are glycoproteins that recognize and bind to specific oligosaccharides

20. selectins are integral proteins of the plasma membrane with lectin-like domains that protrude on the outer surface of mammalian cells