There are 4 main macromolecules that make up life on earth. In the following paragraphs I will talk about Nucleic Acids, Lipids and Carbohydrates. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an original essay 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 5-carbon pentose or deoxyribose sugar covalently bonded to a phosphate group. That phosphate group is covalently bonded to a nitrogenous base. There are 5 nitrogenous bases, however DNA is only made up of 4 of those, which are adenine, thymine, cytosine and guanine. Adenine and cytosine are purines, that is, they are made up of 2 nitrogen rings. Thymine and Guanine are pyrimidines, because they both have a single nitrogen ring. As a polymer, DNA has a double helix, because DNA is composed of 2 chains of nucleotides, connected by phosphodiester bonds, which are held 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, contains Uracil, also a pyrimidine. Additionally, RNA is a single-stranded polymer, meaning 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, wrapped structures of DNA around histone proteins. These are the molecules that possess the information to synthesize the proteins that will give the cell its phenotype. Additionally, chromosomes contain the information to determine a person's sex as 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 transfer RNA. These molecules perform the function of reading the mRNA triplet that is entering the ribosome to be translated into protein and carrying one of 20 types of proteins that match the codon with the anticodon. In this way, tRNA can help the ribosome synthesize a polypeptide. Lipids, another type of macromolecule, are composed primarily 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 saturated with hydrogen atoms. Sometimes, hydrocarbons can be saturated, where two hydrogens are present or not present and the two adjacent carbon atoms form a double bond. At the end there is a carboxyl group. Glycerol is a type of alcohol made up of three carbon atoms with a hydroxyl attached to one end and a hydrogen to the other. These two bond by forming ester covalent bonds 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 are called triglycerides. In short, steroids are formed in a carbon ring structure, fats as triglycerides, and phospholipids as glycerol to which only two fatty acid tails are attached; they are saturated and folded, or saturated and straight. 2 examples are trans fats and phospholipids. Trans fats are unsaturated fats, whose hydrogen atoms are positioned on sides.