Biological Macromolecules: An Overview

• Biological macromolecules are large, organic molecules including carbohydrates, lipids, proteins, and nucleic acids.
• Most macromolecules are organic compounds and their chemical properties are determined by functional groups.
• Biomolecules have a variety of functions, including energy storage and protection.
• Expected learning outcomes: distinguish between carbohydrates, proteins, lipids, and nucleic acids; summarize the general characteristics of each biomolecule; and relate the structures of the biomolecules with their properties.

Terms and Definitions

• Monosaccharide: the simplest form of carbohydrates.
• Monomer: a molecule that can react with other molecules to form very large molecules or polymers.
• Peptide: a short chain of amino acid monomers linked by peptide bonds.
• Hormones: special chemical messengers created in the endocrine gland.
• Amino acids: organic compounds that combine to form proteins.
• Enzymes: proteins that accelerate biochemical reactions.
• Nucleotide: composed of a nitrogen-containing base, a five-carbon sugar, and a phosphate group.
• Phospholipids: contain glycerol, two fatty acids, and a phosphate group.

Carbohydrates

• The term carbohydrate can be broken down as carbon and hydrate; another term is saccharide.
• Carbohydrates are either simple (monosaccharides, disaccharides) or complex (polysaccharides).
• Carbohydrates are the primary energy source for the human body, converting into glucose for ready use.
• Excess consumption of carbohydrates is converted to glycogen and stored in the liver and muscles.
• Glycogen is a slow-releasing carbohydrate.
• Composed of carbon, hydrogen, and oxygen.
• The monomer of carbohydrates is saccharides.
• Examples include: rice, cereal, potatoes, fruits, and pastas.
• Function as the main energy source of the body.

Monosaccharides

• Glucose is used in dextrose and blood sugar, and is utilized by the human body.
• Galactose is found in milk and milk products.
• Fructose is found in fruits and honey.

Disaccharides

• Maltose consists of glucose + glucose, found in malt.
• Sucrose consists of glucose + fructose, found in regular table sugar, sugarcane, and sugar beet.
• Lactose consists of glucose + galactose, found in milk and milk products.

Polysaccharides

• Starch/Amylose is the storage form of glucose in plants.
• Amylopectin is a storage form of glucose in plants.
• Glycogen is the storage form of glucose in animals, stored in the liver and muscles.
• Cellulose is a structural material in plants, specifically in the cell wall of wood, and cannot be digested by humans.

Lipids or Fats

• Lipids are important nutrients, but unhealthy fats like saturated and trans fats can lead to heart disease, cancer, and obesity.
• Lipids function as material for cell membranes, insulation to maintain body temperature, aid in digestion, and as signal molecules.
• Classifications are: triglyceride, phospholipid, wax, and steroid.
• Lipids have varied structures and share the common property of being insoluble in water.
• Fat and oil are the most common examples of lipids under triglycerides.
• They are composed of glycerol and three fatty acids.
• Fat refers to solid triglyceride from animal sources (meat, milk, butter, margarine, eggs, and cheese).
• Oil refers to liquid triglycerides from plant sources (olive oil, corn oil, sunflower oil, and soybean oil).
• Animal fats contain high percentages of saturated fatty acids, while plant oils are mostly unsaturated fatty acids.
• Contain carbon, hydrogen, and oxygen.
• Soluble in oil but insoluble in water.
• Examples: fats and oils.
• Function: long-term storage of energy in the body.
• The monomer of lipids is fatty acids.

Classes of Fats

• Saturated fats have two carbons attached to each carbon (except the one at the end) and are unhealthy, like butter.
• Unsaturated fats are missing at least one hydrogen, are curly in shape, and are healthy, like oils.

Proteins

• Composed of carbon, hydrogen, oxygen, and nitrogen; sulfur and other metals are sometimes present.
• Made up of amino acids.
• The monomer of proteins is amino acids.
• Two proteins classes are saturated and unsaturated.

Examples of Proteins and their Functions

• Keratin is a structural protein found in hair, skin, and nails.
• Fibroin/Silk protein is found in silk. Silk has a smooth and soft texture, is strong, highly resistant to deformation, and a good insulating material.
• Collagen is a major insoluble fibrous protein in connective tissues (tendons, ligaments, skin, cartilage) and the cornea of the eye, making up 30% of proteins in animals.
• Enzymes catalyze chemical reactions by speeding them up, lowering the required energy, or binding substances to specific partners.
  • Lipase aids in the digestion of fats.
  • Pepsin aids in breaking down proteins into peptides (smaller units).
  • Sucrase (invertase) aids in the digestion of sugars and starches.
• Myoglobin is a polypeptide that stores oxygen in muscles, containing a heme group with iron for oxygen storage.

Nucleic Acids

• Play an essential role in the storage, transfer, and expression of genetic information.
• Discovered by Friedrich Miescher in 1868.
• Nucleic acids contain carbon, hydrogen, oxygen, nitrogen, and phosphorus.
• DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are the most common.
• DNA is a nucleic acid that carries the genetic code of organisms, known as the blueprint of life
• RNA carries the information from DNA to cellular factories for protein synthesis.
• Nucleic acids are composed of nucleotides and are also known as polynucleotides.
• They have 3 parts: a nitrogenous base, a five-carbon carbohydrate or sugar, and a phosphate group.
• Contain carbon, hydrogen, oxygen, nitrogen, and phosphorus.
• The monomer is nucleotide.
• Examples: DNA and RNA.
• Function: genetic materials, DNA, and RNA.
• DNA is the blueprint of life as it contains instructions on how to make proteins in the body.

Structures of Biomolecules

• Mnemonic device is CHO CHONP.
  • C stands for Carbon.
  • H stands for Hydrogen.
  • O stands for Oxygen.
  • N stands for Nitrogen.
  • P stands for Phosphorus.