Several depictions of the structure of a 6-carbon compound.

Proteins are incredible - they perform a multitude of functions in the cell, from transporting vitamins to receiving instructions to lowering activation energy as enzymes. The monomer of proteins is amino acids, and when they combine to form chains, they are called polypeptides, as the bond between them is called a peptide bond. However, there are 20 different kinds of amino acids, and by arranging them differently, you can get many different types of proteins - hence the reason that there are tens of thousands of kinds of proteins in your body performing various functions. Proteins are like a biological language, with their letters, words, and sentences. However, what determines how these proteins are created? The process of protein synthesis is called gene expression. I will further describe it a little later in this page. Amino acids consist of an amino group, a carboxyl group, and an R group (determines which amino acid is which). Proteins are very complicated. Thus, there are organizations of its structures. The precise structure of a polypeptide is the order of amino acids in its chain. These polypeptide chains often bend and fold over into local secondary structures, whose overall shape is its tertiary structure. Some proteins have more than one polypeptide chains. These have quaternary structures. Isn't that amazing?

Lipids are interesting because they have no definite monomer, and in contrast to other organic compounds (compounds containing carbon), they are hydrophobic (water-fearing). In this short paragraph, I will elaborate on three main kinds of lipids: fats, phosopholipids, and steroids. Fats are large lipids formed from a glycerol head and three fatty acid tails - hence the reason that a synonym for fat is triglyceride. In fats, the glycerol head consists of three carbons attached to some hydrogens and each bearing a hydroxyl group (an OH, or oxygen-hydrogen molecule). The fatty acid tails consist of a carboxyl group (a COOH group) and a hydrocarbon chain (a chain consisting of hydrogen and carbon atoms), usually about 16-18 carbon atoms long. Fats are storage molecules and can store far more than a carbohydrate can. When one of the hydrocarbon chains in a fatty acid tail has one or more double bonds, there appears to be a kink in the tail. Fats with this kink are known as unsaturated fats. Fats without this kink are known as saturated fats. Saturated fats (found in meat) are easier to stack on top of each other, and the body uses them to store energy. This is what the fat on your body is made out of. Unsaturated fats (oils) are more difficult to stack, due to the kinks in their tails, and is also thus liquid at room temperature. Some food labels consist of the word "partially hydrogenated oils," which means that some of the unsaturated fat inside has been converted to saturated fat by adding oxygen. However, this process creates trans fat, an extremely unhealthy fat linked to many health risks. Gahh, I've ranted for way too long. I need to start talking about one of my favorite molecules in the biological universe - phospholipids. I cannot even explain how much I love these - they're just so cool!!! Phospholipids are just amazing. They make up the cell membrane - which is way more awesome than you think it is. The cell membrane is a semipermeable membrane that seperates the living cell from its environment. But more on that later. For now, you need to know that it is made of phosopholipids, which look considerably like a fat, except that their head has an additional negatively charged phosphate group attached and they only have two fatty acid tails. The fatty acid tails are both hydrophobic, while the glycerol head is hydrophillic (water-loving), due to its negative polarity (water is a polar substance, so it mixes well with other polar substance. I will explain this in another page soon so it makes more sense. Feel free to email me about it as well if you don't understand). Either way, because the tails don't like water and the heads do, the tails force the heads outside and form a layer consisting of two phospholipids, the tails facing inwards and the heads facing outwards - a phospholipid bilayer. This is what the cell membrane is made of. The phospholipid bilayer only allows small, nonpolar molecules to pass through. It is much more difficult for large molecules or polar molecules to pass without the help of an embedded transport protein. Isn't that amazing!!! I'll elaborate on it even more in other pages. But urgh, I have to get to the last type of lipid I wanted to talk about - steroids. Steroids are composed a carbon skeleton with four rings and plays many major roles in the body, like helping with carb regulations, mineral balance, reproductive functions, and more.

The proteins mentioned above were crazy complex - they have amazing structures and are used for so many things! But how do they know which order to assemble in? Do they follow some kind of instruction manual? Actually, yes. Well, kind of. These instructions are actually our final macromolecule - nucleic acids. Proteins are created by following instructions found in genes, which are the unit of inheritance. Genes are made of DNA (deoxyribonucleic acid), which in turn are made of the polymer nucleic acids. Nucleic acids are called nucleic because DNA is found in the nucleus of the cell. There is one more type of nucleic acid - RNA. RNA stands for ribonucleic acid, and it helps carry instructions to the protein synthesis organelles of the cell to instruct the creation of proteins correctly. It looks like one strand of the double helix, but it is not bent in a particular shape. The monomers of nucleic acids are nucleotides, which consist of a five-carbon sugar (deoxyribose is the sugar found in DNA while ribose, a slightly different sugar, is the sugar found in RNA), a phosphate group, and a nitrogenous base. In DNA, there are four nitrogeneous bases:

• Adenine (A)

• Thymine (T)

• Cytosine (C)

• Guanine (G)

These four bases are found in a DNA double helix and they hold all genetic information. On either side of the helix, A goes with T and C goes with G. If you have trouble remembering, think that the Apple goes on the Tree (A goes with T) and the Car goes in the Garage (C goes with G). In RNA, most of the same bases are present, except for T. T is instead replaced with U (uracil). Since the bases are complementary, DNA can be translated into RNA. For example, if one side of a DNA strand goes ACGTTAC, its RNA equivalent would be UGCAAUG. A process that utilizes this advantage is gene expression, which I mentioned earlier - the process of protein synthesis. DNA is first transcribed into RNA. The RNA then goes to a protein synthesis organelle (ribosome) and is translated into a protein.