SC.912.L.18.1: Describe the basic molecular structures and primary functions of the four major categories of biological macromolecules.
Element 14 on the periodic table of elements is better known as Carbon. You may be familiar with carbon in some of its more common forms like; diamonds, carbon dioxide, and graphite (pencil lead). All life on Earth is partially made up from large amounts of carbon, from the molecules that make up your skin, hair, muscles, organs to the very building blocks of your DNA. For this reason life on Earth is also referred to as “Carbon Based Life”. Carbon is capable of playing such a pivotal role in biology because of its ability to form chemical bonds with up to 4 different atoms at a time.
Because of carbon’s capacity to make so many different chemical bonds it can act as the central atom to form trillions of different chemicals. Because of the versatile nature of carbon it serves as the central element in many of the key molecules that support all life on Earth. These key molecules can be organized in the four biomolecules or macromolecules.
4 Biomolecules
Carbohydrates
Carbohydrates, more commonly known as carbs consist of carbon, hydrogen, and oxygen atoms. Energy is stored in the chemical bonds that hold the atoms of the carbohydrate together. When we consume carbohydrates our bodies are digesting the carbs, breaking apart the atoms to release the energy trapped within. Many of the foods we consume contain large amounts of carbohydrates. Virtually every culture on Earth has some staple foods and dishes that are rich in carbohydrates.
Carbohydrates are the body’s primary source of energy and the macromolecule that the body will rely on first for a quick source of energy. The smallest unit of a carbohydrate is a monomer known as a monosaccharide. If two monosaccharides are linked together they form a disaccharide. Many many monosaccharides are connected they form a chain called a polysaccharide.
Lipids
Lipids are also known as “fats”. Lipids are very important for maintaining a healthy body. Lipids have two monomers, glycerol and fatty acid tails. Lipids are our body’s backup energy source once we run out of carbohydrates (sugar) in our bloodstream. Once our blood sugar has sufficiently become depleted our body will burn our fat reserves to keep us functioning, this is where the concept of “burning fat” comes into play. Burning our fat reserves causes us to “lose weight”. Lipids consist of carbon, hydrogen, and oxygen atoms, making them similar to carbohydrates.
Lipids/fat reserves provide insulation. Insulation is the ability to trap or retain body heat. This is why cute baby seals become very big and covered by blubber (layers of fat tissue). This function of lipids is very important for animals who are adapted to survive in cold conditions.
Lipids are also involved in the formation of cellular membranes. In order to grow and maintain healthy cells, our bodies require a sufficient supply of the appropriate lipids. This is of extreme importance when a human fetus is growing brain tissue prior to birth, for this reason many prenatal vitamin supplements contain a large amount of lipids!
Proteins
Proteins are an essential macromolecule that is used to construct our tissues and organs. Without sufficient protein we cannot grow, heal, or function properly. Protein monomers are called amino acids. Proteins consist of the elements carbon, hydrogen, oxygen and nitrogen. Proteins are also involved in the formation of antibodies by our immune systems. The body also uses proteins to form important enzymes.
Foods that are rich in proteins are often meats and animal products. Proteins can also be found in sufficient quantities in some plant products like; tofu, chickpeas, and mung beans. The excess protein taken in by the body is used to create additional hair, if a person becomes deficient in protein their hair can become broken and compromised.
Nucleic Acids
Nucleic acids are the genetic instructions that tell our cells how to function. DNA or DeoxyRibo Nucleic Acid is like the chemical programming for our cells just like how 0s and 1s are the programming for computers. Nucleic Acids consist of the elements carbon, hydrogen, oxygen, nitrogen, and phosphorous. The monomers of nucleic acids are known as nucleotides.
Enzymes
Enzymes are usually large complexes created by combining multiple proteins together. Enzymes are special because they help allow chemical reactions in our bodies to occur much more easily. They do this by acting as catalyst and therefore speed up chemical reactions.
[image of enzymes]
Enzymes speed up chemical reactions by decreasing the amount of energy needed for that reaction to proceed to completion. If you imagine that a chemical reaction is like a boulder that must be pushed up and over a hill an enzyme would actually decrease the size of this hill. If the hill is smaller then the boulder can more easily be pushed!
[insert picture of boulder energy of activiation]
The energy that is required to get over the hill or compete the reaction is known as “the energy of activation” or “activation energy“. This concept is often displayed on a graph called a reaction chart, lines are often used to indicate the activation energy without the enzyme vs with the enzyme.
[enzyme activity chart]
Insulin is a very important enzyme that allows the entry of sugar (carbohydrates) into our cells. Without the appropriate levels of the insulin sugar will remain in the bloodstream causing damage to organs and tissues. Lactase is an enzyme that is responsible for breaking down “Lactose“, the sugar found in milk products. Some people are unable to tolerate lactose and are called “lactose intolerant” because they cannot digest these milk sugars. A protease is an enzyme that helps to digest and break down proteins when they reach our stomach. The suffix “-ase” is often associated with enzymes, so keep an eye out for this when you encounter new scientific terms.
[image of insulin, lactaid]
Enzymes have very specific functions, and those functions are determined by their unique three-dimensional structures. Enzymes and all proteins can change shape if they are placed in environmental conditions that are extremely different than the one they were designed for. If a stomach enzyme that is designed to work in a pH of 1-2 travels to your small intestine which has a pH of 6-7.4 the enzyme will change shape and lose its ability to function. This changing of shape and loss of function is called “Denaturing“. Changes in; temperature, pH, and salinity some examples of what can cause protein/enzyme denaturation to occur. Humans have been denaturing the proteins of microbes to preserve foods for thousands of years by smoking, salting, and cooking foods.
[insert image of protein denaturation]
