Macromolecules

Key Vocabulary

Macromolecule: A macromolecule is a large and complex molecule composed of smaller subunits called monomers. Macromolecules are typically found in biological systems and are vital for various biological processes and functions.
Monomer: A monomer is a small and relatively simple molecule that can chemically bind with other monomers to form a larger, more complex molecule known as a polymer. Monomers are the building blocks of polymers.
Polymer: A polymer is a large molecule made up of repeating subunits called monomers, connected through chemical bonds.
Dehydration: refers to the process of joining monomers together to form a polymer while simultaneously releasing a water molecule as a byproduct.
Hydrolysis: the process of breaking down polymers into their constituent monomers by the addition of a water molecule.
Carbohydrate: Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen atoms. They serve as a primary source of energy for living organisms and are classified into three main types: monosaccharides (simple sugars), disaccharides (two sugar units linked together), and polysaccharides (long chains of sugar units).
Lipid: a diverse group of organic compounds that are insoluble in water but soluble in nonpolar solvents. They play essential roles in energy storage, insulation, cushioning, and as structural components of cell membranes, and include molecules such as fats, oils, phospholipids, and steroids.
Protein: large molecules composed of amino acids linked together by peptide bonds.
Enzyme: specialized proteins that act as catalysts in biological reactions, facilitating and speeding up these reactions without being consumed or permanently altered in the process.
Nucleic Acid: macromolecules that are crucial for storing, transmitting, and expressing genetic information in living organisms. They are composed of nucleotide subunits and come in two primary forms: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid)

Macromolecules

Dehydration Synthesis and Hydrolysis

There are two key processes involved in the formation and breakdown of polymers: dehydration synthesis (also known as condensation) and hydrolysis.

Dehydration synthesis is the process by which monomers are joined together to form a polymer, and a water molecule is produced as a byproduct. During this process, a hydroxyl group (-OH) from one monomer combines with a hydrogen atom (-H) from another monomer, creating a covalent bond. This bond formation releases a water molecule. This reaction undergoes repeated cycles, building a polymer chain and releasing a water molecule with each bond formation.

On the other hand, hydrolysis is the reverse process of dehydration synthesis. It involves breaking down polymers into their individual monomers by adding a water molecule. In hydrolysis, a water molecule is split into a hydroxyl group (-OH) and a hydrogen atom (-H). The hydroxyl group attaches to one monomer, while the hydrogen atom attaches to the adjacent monomer, breaking the covalent bond between them and separating the monomers.

Types of Macromolecules

There are four major types of macromolecules found in living organisms: carbohydrates, proteins, nucleic acids, and lipids. Let’s go through each type together!

Carbohydrates

Carbohydrates, often called “sugars” or “starches”, are molecules composed of carbon, hydrogen, and oxygen atoms. They serve as a primary source of energy for all living organisms. Monomers join together to form carbohydrates and have the formula C_nH_2nO_n. Typically, these monomers have 3, 4, 5, or 6 carbon atoms. These basic units when combined are called monosaccharides. Examples of monosaccharides include glucose (C₆H₁₂O₆) and fructose. When two monosaccharides join together through dehydration synthesis, they form a disaccharide (e.g., sucrose).

An oligosaccharide is a type of carbohydrate composed of a relatively small number of monosaccharide units, typically between 3 and 10 sugar molecules. It is larger than a monosaccharide but smaller than a polysaccharide. Oligosaccharides are found in various biological systems and can serve as structural components, signaling molecules, or energy sources.

Many monosaccharides linked together create polysaccharides like starch and cellulose, which are used for energy storage and structural support, respectively. Animals, including humans, store glucose (monosaccharide) in the form of long glycogen (polysaccharide) chains. Glycogen is formed through a process called glycogenesis (a dehydration synthesis). In animals, glycogen is stored in the liver and muscle tissue. Any time glucose is needed for cellular energy production, glycogen is hydrolyzed into glucose.

In plants, carbohydrates are stored primarily in the form of starch. Starch is a polysaccharide composed of glucose units and serves as an energy reserve in plants. It is stored in specialized plant structures called storage organs, such as roots, tubers, seeds, and fruits.

Carbohydrates exist in various shapes and sizes! Carbohydrates can exist in linear or branched forms. In linear carbohydrates, the monosaccharide units are arranged in a straight chain. A common linear monosaccharide is cellulose, which forms the structural component of plant cell walls.

Branching occurs when additional monosaccharide units are attached to the main chain, creating side branches. This branching can be regular or irregular. For instance, glycogen and amylopectin are highly branched carbohydrates found in animals and plants, respectively.

Lipids

Lipids are a diverse group of molecules that include fats, oils, waxes, and steroids. They are all hydrophobic, meaning they do not dissolve in water. Lipids serve as long-term energy storage, insulation, and protection for organs. They are made up of fatty acids and glycerol. Fatty acids are long chains of carbon atoms with hydrogen atoms attached.

Lipids can be saturated (containing only single bonds between carbon atoms) or unsaturated (containing one or more double bonds between carbon atoms).

lipids found in living organisms.

Lipids play vital roles in energy storage, insulation, cushioning, and the structure and function of cell membranes. Understanding the different types of lipids and their functions helps us appreciate their importance in maintaining the health and functioning of living organisms.

Proteins

Proteins are essential for the structure, function, and regulation of cells and tissues in our bodies. They are made up of long amino acid monomer chains. Amino acids are made of a centrally located carbon, an amine group, a carboxylic acid, and a side group. There are 20 different amino acids. Each amino acid has different properties due to its side group. These varying side groups give each protein its various properties and structures. The link between amino acids is a covalent bond called a “peptide bond”. Proteins have a specific three-dimensional shape that determines their function. They can act as enzymes, antibodies, transport molecules, and perform many other vital roles in the body.

Proteins can have different shapes and functions. For example, globular proteins are typically soluble in water (hydrophilic) and perform functions such as enzyme catalysis, transport, and signaling. An example is hemoglobin, a globular protein that carries oxygen in red blood cells. Fibrous proteins have long, fiber-like shapes. They are often involved in providing structural support and strength. Collagen, found in connective tissues like skin and tendons, is a fibrous protein that helps maintain the structural integrity of these tissues.

Enzymes are remarkable proteins that play a crucial role in biochemical reactions. Enzymes lower the activation energy required for a chemical reaction to occur, making the reaction faster and more efficient. They are highly specific, acting on specific substrates (molecules they act upon) like puzzle pieces fitting together. This specificity allows enzymes to carry out specific tasks in the body. Enzymes are not consumed or altered during the reaction; they can be used repeatedly, making them essential for various biological processes.

Nucleic acids

Nucleic acids are composed of smaller units called nucleotides. Each nucleotide consists of a sugar molecule, a phosphate group, and a nitrogenous base. Nucleic acids are polymers made of nucleotides that contain carbon, hydrogen, oxygen, nitrogen, and phosphorus. Nucleic acids are responsible for storing and transmitting genetic information. The two main types of nucleic acids are DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).

DNA is a double-stranded helix that stores genetic information and carries the instructions for building and maintaining an organism, while RNA is involved in protein synthesis. The sequence of nucleotides in DNA and RNA determines the genetic code and the traits of an organism. DNA contains nucleotides made up of a deoxyribose sugar, one of four nitrogenous bases (adenine, guanine, thymine, and cytosine), and a phosphate group. Genes are made up of DNA. In humans, genes can contain a few hundred DNA bases to more than a million vases. Genes are located on chromosomes. As you may recall, chromosomes are located in the nucleus of a cell. Genes provide signals directing actions.

RNA consists of a single strand of nucleotides. The structure of RNA is similar to DNA, except it contains a ribose sugar molecule. Additionally, RNA has the same nitrogenous bases as DNA, except it contains uracil instead of thymine. There are three main types of RNA: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).

mRNA carries the genetic instructions from DNA to the protein-making machinery in the cell. tRNA brings amino acids to the ribosomes during protein synthesis. rRNA is a crucial component of ribosomes, the cellular machinery where proteins are assembled.

RNA functions as a messenger, translator, and builder in the cell. It helps in the synthesis of proteins, which are essential for various cellular processes. RNA also plays a role in regulating gene expression and controlling cell functions. It acts as a crucial link between DNA and proteins, facilitating the transfer and execution of genetic information.