Biomolecules [BIOLOGY]

• Carbon

  Life on earth is based on the element carbon. The most important characteristics of carbon as the basis for the chemistry of life is its capability of forming up to four valence bonds with other atoms simultaneously, and the energy needed to create or break a bond with a carbon atom is at a level appropriate enough for building large and complex molecules which are stable and reactive.
• Carbon

  Carbon atoms also bond readily with other carbon atoms through the process known as catenation, allowing the creation of long macromolecules and polymers. Per Stephen Hawking: “What we normally think of as life is based on chains of carbon atoms.”
• Carbon

  Carbon is capable of forming vast numbers of compounds than any other element, ten million described to date and maybe even more.
• To recall, the cell is the functional unit of life. The most abundant element in cells is hydrogen (H), followed by carbon (C), oxygen (O), nitrogen (N), phosphorus (P), and sulfur (S). These elements are called macronutrients. Some elements are required by some cells in very small amounts and are called micronutrients or trace elements. All of these elements are essential to the function of many biochemical reactions, and therefore, are essential to life.
• A big chunk of carbon-containing compounds has led to a distinction between organic and inorganic molecules or compounds (the latter do not contain carbon). Organic compounds in organisms are generally larger and more complex than inorganic compounds. All these groups of molecules are called biomolecules because they are part of living matter and contain carbon, which is the building block of life.
• In addition to carbon, biomolecules also contain functional groups—groups of atoms within molecules categorized by their specific chemical composition and the chemical reactions they perform, regardless of the molecule in which the group is found. Carbon chains form the skeletons of most organic molecules. Functional groups combine with the chain to form biomolecules.
• Because these biomolecules are typically large, they are also called macromolecules. Many macromolecules are formed by linking together identical, or very similar, smaller organic molecules. The smaller molecules act as building blocks and are called monomers, and the macromolecules that result from their linkage are called polymers
• Cells link monomers to form polymers by means of dehydration reaction, a reaction that removes water as two molecules are bonded together. Not only must cells make macromolecules but they must also have to break them down. Imagine how our food is able to energize us, our body is able to digest the larger food compounds into bits and chunks before they can be distributed throughout the body, providing energy.
• This digestion is called hydrolysis and is essentially a reverse to dehydration reaction, in that water helps break the bond between molecules hence why it feels easier to eat while drinking fluids. Both reactions require the help of enzymes to make and break the bonds. Enzymes are specialized macromolecules that speed up reactions in cells. In cases of people with lactose intolerance, they lack the enzymes needed to break down the sugar lactose.
• Cells and cell structures include four main groups of carbon-containing macromolecules: carbohydrates, lipids, proteins, and nucleic acids.
• Carbohydrates are the most abundant biomolecules. They are mainly composed of carbon, hydrogen, and oxygen atoms. They carry out functions such as:

  • Serve as a major source of energy
  • Facilitate cell to cell recognition
  • Provide structural support and framework
  • Serve as a component of nucleic acids
• Carbohydrates

  • Monosaccharides
  • Disaccharides
  • Oligosaccharides
  • Polysaccharides
• Monosaccharides

  • Triose
  • Pentose
  • Hexose
• Disaccharides

  • Sucrose
  • Lactose
  • Maltose
• Oligosaccharides

  • Raffnose
  • Stachyose
  • Galactooligosaccharide
• Polysaccharides

  • Starch and glycogen
  • Cellulose
  • Peptidoglycan
  • Chitin
• Monosaccharides are also called simple sugars because they are the monomers or building blocks of carbohydrates. They generally have a molecular formula that is some multiple of CH2O.
• Monosaccharides

  glucose, the sugar most important to live, is C6H12O6 (6 times the CH2O). Because molecules can be arranged, it is possible that biomolecules contain the same number of elements but have different structures, these are called isomers.
• Monosaccharides

  the sugar fructose also has the chemical formula C6H12O6 but it differs structurally from glucose. Slight changes in structure give isomers different properties, most notably how they would react with other molecules. This difference for instance is why fructose is much sweeter than glucose.
• Monosaccharides

  The carbon skeleton of glucose and fructose is six carbon atoms long but other monosaccharides may have three to seven carbons. Five-carbon sugars, pentoses, and six-carbon sugars, hexoses, are among the most common.
• Monosaccharides

  Triose is the simplest monosaccharide that contains three-carbon molecules.

  • Example: Glyceraldehyde in glyceraldehyde 3-phosphate, a molecule involved in photosynthesis.
• Monosaccharides

  Pentose contains five carbon atoms.

  • Examples: ribose and deoxyribose found in RNA and DNA.
• Monosaccharides

  Hexose has six carbon atoms in the molecule.

  • Examples: glucose, galactose, and fructose
• Monosaccharides

  Sugars are often drawn as if their carbon skeletons are linear but in aqueous solutions, most five- and six-carbon sugars form rings.
• Earlier, we mentioned an enzyme that breaks down the sugar lactose. That enzyme is called lactase. Note that most names for sugars end in -ose and for enzymes, end in -ase.
• Monosaccharides, particularly glucose, are the main fuel for cellular work. Energy is released when bonds are broken and glucose, due to its simple structure, provides an immediate energy source to cells. Cells also make use of their carbon skeleton as material for making other kinds of organic molecules.
• Disaccharide

  When two monosaccharide monomers are linked by means of a dehydration reaction, a disaccharide is formed. Sucrose is the most common disaccharide and it is made by joining glucose with fructose. Transported in the plant sap, sucrose provides energy and raw materials to all parts of the plant. We can extract sucrose from the stems of sugarcane or roots of sugar beets to use as table sugar
• Disaccharides are formed by linking two monosaccharides together.

  • Sucrose is also known as table sugar which is a combination of glucose and fructose.
  • Lactose is composed of glucose and galactose and is mostly found in milk; also known as milk sugar.
  • Maltose or malt sugar is formed when two units of glucose are combined.
• Polysaccharides

  Polysaccharides are macromolecules, polymers of hundreds to thousands of monosaccharides linked by dehydration reactions. They may function as storage molecules or as structural compounds. Starch is a storage polysaccharide in plants consisting of chains of glucose. These glucose monomers may coil into a helical shape and may be unbranched or branched. Starch granules serve as carbohydrate reserves from which plant cells can withdraw glucose.
• Polysaccharides

  Humans and most other animals have enzymes that can hydrolyze starch to glucose. Potatoes and grains are major sources of starch in the human diet. Animals store glucose as a polysaccharide called glycogen. In the body, glycogen is stored as granules in the liver or our muscle cells. The glycogen is hydrolyzed to release glucose when it is needed.
• Polysaccharides

  Another polysaccharide is a major component of the tough walls that enclose plant cells, cellulose. It is the most abundant organic compound on Earth, and the way its monomers are arranged allows it to form cable-like microfibrils. These microfibrils, combined with other polymers, produce strong support for trees and the structures we build with lumber.
• Polysaccharides

  As we do not have enzymes that can break the glucose bonds in cellulose, it is not a nutrient for us but it still contributes to our digestive health as “fiber”. Fresh fruits, vegetables, and whole grains are rich in fiber. Insects and crustaceans build their exoskeletons, the hard enclosing case of the animal, with the polysaccharide chitin. Chitin also makes up the cell walls of fungi.
• Oligosaccharides are three to ten units of monosaccharides linked together. It came from the Greek word oligo, which means “few.”
• Lipids

  • Fatty acids
  • Phospholipids
  • Waxes
  • Steroids
• Fatty acids

  • saturated
  • unsaturated
• Steroids

  • Cholesterol
  • LDL
  • HDL
• Lipids

  Similar to carbohydrates, lipids also contain hydrogen, carbon, and oxygen. However, unlike carbohydrates, lipids are water-insoluble and are structurally diverse. They can be classified as fatty acids, waxes, steroids, and phospholipids. Lipids serve the following functions:

  • Serve as energy storage
  • Give thermal insulation
  • Component of cell membranes
  • Act as a signaling molecule
  • Facilitate absorption of fat-soluble vitamins
• Lipids

  They are thus hydrophobic and you can see their chemical behavior when you mix oil with water or how some fat floats in a broth. Lipids differ from other biomolecules in that they are neither huge macromolecules nor are they polymers built from similar monomers.
• Fatty acids

  Fat is a large lipid made from two types of smaller molecules: glycerol and fatty acids. Glycerol consists of three carbons, each having a hydroxyl group (-OH). A fatty acid consists of a carboxyl group (-COOH) and a hydrocarbon chain. The hydrocarbon chain is the reason fats are hydrophobic. In a way, you can consider the glycerol as the head and because the hydrocarbon chain is lengthy, it can be referred to as the tail.
• Fatty acids

  A fatty acid whose hydrocarbon chain has one or more double bonds is called an unsaturated fatty acid. These double bonds cause kinks (or bends) in the carbon chain. If a fatty acid lacks this double bond, all its hydrocarbon chain contains the maximum number of hydrogens attached per carbon atom (hence it is “saturated” with hydrogens) and is called a saturated fatty acid.