LEQ: How do biological molecules store information? Reading 32.1, 2.3 Activator: foundations In your group, discuss how a building is built. Where does a contractor start, what materials will he/she need, etc. Key terms – monomer, polymer, carbohydrate,

Carbon atoms have unique bonding properties Covalently bond with up to four other atoms: Straight chains Branches Rings Carbon is the central atom of biological chemistry. This atom is uniquely suited to form up to four single covalent bonds. These bonds are stable, share electrons equally with many different elements, and are long-lasting. Its versatility in forming different arrangements is also unrivaled in biological chemistry. Carbon can easily bond with itself to form straight chains, branching patterns, and even ring structures that add surface area and occupy space in biological molecules. This arrangement in molecular structure will suit a unique biological function .

Monomers individual subunits (various types) Biomolecules that consist of monomers have the potential to store information. Based on sequence Monomers individual subunits (various types) Polymers are made of many monomers. Biomolecules are molecules that are made or consumed by biological organisms. Certain molecules have the potential to store information; meaning that because the molecule is assembled by ordering subunits together in acharacteristic fashion, a meaning can be associated with it. This idea is easy to understand , if you consider how a word is constructed. A word consists of different letters put together in characteristic sequence. Change the sequence of the letters changes the meaning and appearance of the word. The letters in the biological alphabet are called monomers and the assemblage of this alphabet is called a polymer. Each biomolecule that is also a polymer has its own unique chemical language. We’ll consider the monomeric alphabet of carbohydrates next.

Carbohydrates have roles in energy storage and cellular structure: Polymer: polysaccharide Monomer: monosaccharide Carbohydrates are biomolecules that have roles in energy storage and forming cellular structures such as cell walls in some organisms such as plants and fungi. Each monomer is called a monosaccharide and a common carbohydrate monomer, glucose is shown above. Note all that oxygen, this molecule is very polar and will readily dissolve in water (hydrophilic).

Sources of carbon for building new molecules Polymer (starch) Starch is a polymer of glucose monomers that often has a branched structure. Sources of carbon for building new molecules Polymer (cellulose) Cellulose is a polymer of glucose monomers that has a straight, rigid structure Polysaccharides are often highly redundant, consisting of the same monomers of glucose covalently bonded together. A molecule such as starch is high redundant and information-poor (the equivalent of saying the letter “A” over and over again). Nonetheless, a close comparison between starch and cellulose (below) will give up some important details. Starch has unique covalent bonds arranged in a pattern that allow long chains of glucose to form and also bond to adjacent chains of glucose (above, top). Cellulose is different in that each glucose is bonded to the adjacent glucose in a way different from starch causing the chain to orient itself differently in space. Despite the fact that both molecules are made using the same repetitive building block, their unique functions are due to not what they are made of, but how that monomer is arranged. So, it’s kind of a boring language to learn (sorry glycobiologists), but it demonstrates the possibility of encoding information – all that is needed is for differences between monomers. Two other biomolecules have a much larger “alphabet” and encode biological information. More tomorrow. Highly redundant structure – “information poor”

Summary: Explain the relationship between a polymer and monomer: Use an example, analogy or metaphor that is “informational”

Proteins are large molecules made of amino acids. Twenty (two) different amino acids are used to build proteins in organisms. Amino acids have unique properties based on R groups: left: general amino acid structure Serine (below) is polar (hydrophilic)

Polypeptides consist amino acids linked by peptide bonds.

Polypeptides differ in number and order of amino acids. A protein is made of at least one polypeptide Amino acids interact to give a protein its shape. hydrogen bond Hemoglobin Incorrect amino acids change a protein’s structure and function.

Nucleic acids are biomolecules consisting of monomers called nucleotides.

Nucleotides have three parts: A phosphate group nitrogen-containing molecule, called a base deoxyribose (sugar)

Polynucleotides have unique sequences of bases Capable of hydrogen bonding with other polynucleotides

Questions: two-minute talks Explain how polymers are a source of information for cells: how do cells store this information? Create an analogy to describe the relationship between polymers and words/alphabet.

Lipids are nonpolar macromolecules that include fats, oils, and cholesterol. Not a polymer, but have “parts” Many contain fatty acids bonded to glycerol (sugar):

Saturated fat Fats and oils have different types of fatty acids. Unsaturated fats can be liquid at room temp Saturated fats are solid at room temp Saturated fat double bond causes bending

Cholesterol is a steroid; used to make hormones and cell membranes

Phospholipids have polar “heads” and nonpolar “tails” Hydrophilic head Phosphate Glycerol Fatty acids Hydrophobic tails Hydrophilic head Hydrophobic tails (a) Structural formula (b) Space-filling model (c) Phospholipid symbol

Summary: Biomolecule Monomer or basic components Polymer or types Function(s) Looks like: Carbohydrate Nucleic acid Protein Lipid

Summary: What are the four main classes of macromolecules? Which include polymers? What is the relationship between a polymer and monomer? Explain how both nucleic acids and proteins are polymers. Be sure to describe the monomers that make up the polymers. How are carbohydrates and lipids similar? How are they different? Explain how the bonding properties of carbon atoms result in the large variety of carbon-based molecules in living things.