Four Main Macromolecules that Make Up Life on Earth

There are 4 main macromolecules that make up life on earth. In the following paragraphs, I will be talking about Nucleic Acids, Lipids, and Carbohydrates.

There are 2 structures of Nucleic Acids, which are DNA, or deoxyribonucleic acid, and RNA, or ribonucleic acid. Both of these molecules are composed of monomers called nucleotides that covalently bond to form a polymer. Nucleotides are composed of three basic functional groups, a phosphate group, a nitrogenous base, and a pentose. DNA is made up of the pentose or 5 carbon sugar deoxyribose that is linked covalently to a phosphate group. That phosphate group is covalently linked to a nitrogenous base. There are 5 nitrogenous bases, however, DNA is only made of 4 of those, which are Adenine, Thymine, Cytosine, and Guanine. Adenine and Cytosine are purines, which means they are made of 2 rings of nitrogen. Thymine and Guanine are, on the other hand, pyrimidines, because they both have a single ring of nitrogens. As a polymer, DNA has a double helix, because DNA is composed of 2 chains of nucleotides., linked by phosphodiester bonds, that are maintained together by hydrogen bonds formed between purines and pyrimidines on opposite chains. On the other hand, RNA is different from DNA. RNA, instead of containing the nitrogenous base Thymine, it contains Uracil, which is also a pyrimidine. Additionally, RNA is a single stranded polymer, meaning that it does not form hydrogen bonds with another strand in its normal state.

Two examples of molecules that belong to nucleic acids are chromosomes and transfer RNA or tRNA. Chromosomes are condensed and coiled structures of DNA around histone proteins. These are the molecules that have the information to synthesize the proteins that will give a cell its phenotype. Additionally, chromosomes contain the information to determine a person’s sex as a male or female. This is usually stored in the last pair of chromosomes. In fact, chromosomes contain alleles, which are alternative forms of genes that code for a specific trait. Another example of a molecule that is a nucleic acid is the transfer RNA. This molecules carry out the function of reading the triplet of the mRNA that is coming into the ribosome to be translated into protein and bringing one of the 20 types of proteins that match the codon with the anticodon. Like this, the tRNA is able to help the ribosome synthesize a polypeptide.

Lipids, another type of macromolecule, are composed mainly of carbon, oxygen, hydrogen, and phosphorus. There are types of lipids: phospholipids, steroids, and fats. The main monomers of lipids are glycerol and fatty acids. Fatty acids are hydrocarbon chains: carbon chains either saturated with hydrogen atoms. Sometimes, hydrocarbons can saturated, in which two hydrogens are made or not present and the two adjacent carbon atoms form a double bond. At the end is a carboxyl group. Glycerol is a type of alcohol made of three carbons with a hydroxyl attached to one end, and a hydrogen to the other. These two bond by forming covalent ester linkages between the hydroxyl of the carboxyl group of the fatty acid and the hydrogen through dehydration synthesis. When three fatty acids are attached to a glycerol, the remaining molecules called triglycerides. In short, steroids are formed in a carbon ring structure, fats as triglycerides, and phospholipids as glycerol with only two fatty acid tails attached to it; are saturated and bent, or saturated and straight.

2 examples are trans fats and phospholipids. Trans fats are unsaturated fats, whose hydrogen atoms are positioned on opposite sides, making it straight, and able to compact as a solid. These are bad since they can tightly pack in blood vessels and cut blood flow. Another example is phospholipids. These are a glycerol with two fatty acids and another has a hydrogen attached to a phosphate. These make their tails of fatty acid non polar and glycerol and phosphate are polar. This means that the polar sides are hydrophilic and the nonpolar tails are hydrophobic.

Carbohydrates are structures in rings and chains. They are made of hydrogens bonded to carbons and hydroxyl groups to carbon. There is also a carbonyl group, that based on its position, it makes it an aldehyde or ketone. There are alpha and beta links because of carbons.

2 examples are cellulose that makes up the cell wall of a plant cell, and, and starch that contains glucose molecules that are used as stored energy to carry out cellular respiration and produce ATP.

C. Monomers are joined by dehydration synthesis, which is removing a water vy joining a hydroxyl group and a hydrogen atom. This is how monomers build polymers.