Chemistry in Living Things

Organic Compounds: Molecules that are found in living things. Organic compounds contain carbon. Why Carbon? With an atomic number of 6, carbon has 4 valence (outer) electrons, in the 2nd energy level which holds 8 electrons. Because it needs to share 4 electrons (form 4 bonds) to be stable, it can form bonds with a wide variety of elements and form complex molecules.

4 Main Types of Organic Molecules Carbohydrates Lipids (Fats and Oils) Proteins Nucleic Acids (DNA and RNA) Many organic molecules are polymers, which means they are chains of many smaller building blocks. (poly = many) Also called macromolecules, because they are very large. (macro = large)

Types of Carbohydrates Carbohydrates are composed of Carbon, Hydrogen and Oxygen in a ratio of (about) 1:2:1 Example: Glucose is C6H12O6 Types of Carbohydrates Monosaccharides- Disaccharides- Example: Sucrose = Glucose + Fructose simple sugars (like glucose) 2 sugars linked together

Types of Carbohydrates Cont. Polysaccharides- Examples: Starch- Cellulose- Glycogen- energy storage in animals polymers of many sugars energy storage in plants structural component of plant cell walls

Lipids (Fats and Oils) Lipids are insoluble in water. Nonpolar molecules due to a large proportion of C-H bonds. Functions of lipid include: Energy Storage Insulation Protective coating Lipids contain twice as many calories per gram as carbohydrates or proteins.

Proteins Proteins are made of subunits called amino acids. There are 20 types of amino acids.

Amino Acids Each amino acid has a central carbon, with 4 different attachments: an amino group (NH2), a carboxyl group (COOH), a hydrogen and a side group (represented with an R). It is the side group(R) that differs among the 20 types of amino acids.

The 20 Amino Acids in Proteins

Protein Functions Some of the functions of proteins include: Transport proteins Example: Hemoglobin transport O2 -- Enzymes : proteins that catalyze a specific chemical reaction Example: Pepsin digest proteins Contractile proteins for movement Example: Muscle fibers Structural proteins Example: Keratin in hair

Levels of Structure in Proteins Primary structure: The order of amino acids Secondary structure: Regular folding or pleating Tertiary structure: Folded 3- dimensional shape Quaternary structure: Proteins that have more than one polypeptide chain joined together. Animation: http://www.stolaf.edu/people/giannini/flashanimat/proteins/protein%20structure.swf

The 3-dimensional shape of a protein is important for its function. Under certain conditions, a protein may become unfolded and will not be able to perform its function. This unfolding of a protein is called denaturation.

Nucleic Acids Composed of subunits called nucleotides. There are 2 Types of Nucleic Acids: DNA and RNA Stores hereditary information in the cell by the order of the bases A, C, T and G

Synthesis (Building) of Polymers: Dehydration (or Condensation) Reactions Many polymers are built by reactions called dehydration (or condensation) reactions. An OH group from one subunit is linked with a H on the other subunit, forming water. The subunits are linked covalently together.

Breaking down Polymers: Hydrolysis Reactions When sugars, proteins or lipids are broken down into their subunits, the opposite process occurs. Water is used in this process to break apart the polymer, so it is called a hydrolysis reaction. (hydro= water, lysis= to break)

When 2 amino acids are linked together by a condensation reaction, the bond is called a peptide bond.

Animation of condensation and hydrolysis reactions http://www.biotopics.co.uk/as/disaccharideformation.html http://www.tvdsb.on.ca/Westmin/science/sbioac/biochem/condense.htm http://www.biotopics.co.uk/as/aminocon.html

Explain the difference between carbohydrates and fats. Carbohydrates are made of carbon, hydrogen and oxygen in a ratio of approximately 1:2:1. Example: Ribose C5H10O5 Fat molecules are mostly hydrocarbons, with a much lower percentage of oxygen Example: Palmitic Acid CH3(CH2)14COOH Both are sources of energy (excess sugars can be converted by the body to fat)

Why do animals store most of their excess energy as fat rather than starch? Fats have 2 times as much energy per gram as carbohydrates or proteins (Twice as many calories per gram) so more energy can be stored without reducing mobility.