entropy

Entropy is chaos, disorder, randomness.
According to the second law of thermodynamics, everything that happens in the universe leads to more disorder, everything increases in complexity over time.
Disorder puts energy in a usable form (free energy), sometimes a system may seem like it's getting more organized but more work is required, leading to even more chaos.

Law of Thermodynamics

The 3 Laws of Thermodynamics are:

1. Conservation of mass-energy: Energy can neither be created nor destroyed, they can only be converted from one form to another
2. Law of Entropy: all spontaneous events act to increase the total entropy (measurement of disorder/chaos)
3. Absolute Zero: absolute zero is removal of all thermal molecular motion

Second Law of Thermodynamics with reference to metabolic processes:

Living organisms constantly use anabolic processes to build highly ordered structures such as proteins, DNA, and membranes.  These are endergonic reactions which are not spontaneous and uses up energy.  This seems to violate the second law of thermodynamics by decreasing the amount of disorder and increasing the free energy.  However, in reality, every 'order' created by anabolic processes are actually followed by an even greater disorder caused as these catabolic processes release energy.  The overall (net) free energy is less than 0, more disorder is created, which supports the second law of thermodynamics.  

macromolecules

Deoxyribonucleic Acids

• It is a polymer made up of nucleotides (adenine, thymine, cytosine, guanine), ribose sugar, and phosphate.
• It contains phosphodiester bonds, hydrogen bonds, and glycosyl bonds.
• The functional groups in this macromolecule are carbonyl and hydroxyl groups.
• Functions: contains genetic material for inheritance and replication, protein synthesis, and reproduction
• Characteristics: it has a double helix shape with the two strands running antiparallel to each other.

Carbohydrates

(maltose)

• Empirical formula: (CH₂O)_n 
• Carbohydrates may be classified into three groups: monosaccharides, oligosaccharides, and polysaccharides.
• Simple sugars can have spatial arrangement of their atoms, forming isomers with different chemical properties (e.g. glucose, galactose, and fructose)
• Monosaccharides are monomers that can undergo condensation reaction to form dimers (e.g. maltose, sucrose), or polymers.  
• Bonding between the monomers are glycosidic linkage (covalent bonds), the condensation reaction also produces a biproduct of water
• Function: energy storage, structural support, building materials, cell surface markers for cell-to-cell identification and communication
• Characteristics of Carbohydrates (polymers): can be straight chain or branched
• Examples: fructose, glucose, sucrose maltose, lactose, amylose, amylopectin, cellulose, glycogen, chitin

Proteins

(keratin)

• Amino acid polymers folded into specific 3-D shapes.  Its structural characteristics determine its function.
• An amino acid is an organic molecule with a central carbon atom attached to an amino group, a carboxyl group, a hydrogen atom, and an R chain.
• Monomers of protein polypeptide bonds to form polypeptide chains into polymers through condensation reaction
• Functions: signal transduction, cell cycle regulation, differentiation, structural building blocks
• Characteristics: may be polar, nonpolar, or charged, low molecular weight
• Examples: keratin, fibrin, collagen

Lipids

(cholesterol)

• Hydrophobic molecules composed of carbon hydrogen, and oxygen.
• They are polar molecules
• Lipids can be divided into four families: fats, phospholipids, steroids, and waxes.
• Triglycerides are lipids containing three fatty acids attached to a single molecule of glycerol
• Glycerol reacts with fatty acids through a condensation reaction between the hydroxyl group of glycerol and the carboxyl group of a fatty acid.  The bond is called an ester linkage. (esterification)
• Functions: energy storage, membrane structure, hormones, vitamins
• Examples: cholesterol (steroids), testosterone, butter, cutin, beeswax