All living things consist of basic units of matter called atoms.


 The atom 



















Molecules form when atoms bond with one another.


   [3-D water structure, showing that the charge distribution is lower around the hydrogen atoms]



















Inorganic molecules are often associated with nonliving things, and organic molecules are associated with living organisms.  Several classes of organic molecules have biological significance.  In this lab, you will be studying proteins, carbohydrates (monosaccharides, disaccharides, polysaccharides), and lipids (i.e., fat).


Large organic molecules form during dehydration synthesis (also called condensation synthesis)  when smaller molecules bond as water is given off. 




dehydration synthesis


















During hydrolysis, bonds are broken as water is added. 




Go to the following website and look at the short Flash animation on condensations synthesis and hydrolysis.  Note the role of the enzyme.



A fat contains one glycerol and three fatty acids. 

Go to the following website and look at the short Flash animation on the formation of a lipid.  In the explanation, note the difference between a triglyceride that is an oil and one that is solid.


Proteins and carbohydrates called polysaccharides are macromolecules because they contain a large number of subunits. 


Proteins contain a large number of amino acids (the subunit) joined together by a peptide bond. 

Go to the following website and look at the short Flash animation on the formation of proteins.  In the explanation, note what determines how the amino acid "behaves". What is responsible for catalyzing the reaction between the amino acids?


A polysaccharide such as starch contains a large number of glucose molecules joined together.


Various chemicals can be used to test for the presence of specific organic molecules.  Most often, a particular color change is looked for.  If the change is observed, the test is said to be positive because it indicates that the molecule is not present.


A control is included in each experiment for comparison.  The control goes through all the steps of the experiment, but it lacks the factor being tested.  This missing factor allows you to observe the difference between a positive result and a negative result.  If the control sample tests positive, then you know your test is invalid.




Proteins have numerous functions in cells.  Antibodies are proteins that combine with pathogens so that the pathogens are destroyed by the body.  Transport proteins combine with and move substances from place to place.  Hemoglobin transports oxygen throughout the body.  Albumin is another transport protein in our blood.  Regulatory proteins control cellular metabolism in some way.  For example, the hormone insulin regulates the amount of glucose in blood so that cells have a ready supply.  Structural proteins include keratin, found in hair, and myosin, found in muscle.  Most enzymes are proteins.  A reaction that could take days or weeks to complete can happen with an instant if the correct enzyme is present.  Amylase is an enzyme that speeds the breakdown of starch in the mouth and small intestines.


Proteins are made up of amino acids joined together.  About twenty different common amino acids are found in cells.  All amino acids have an acidic group (-COOH) and an amino group (H2N-).  They differ by the R group (remainder group) attached to the carbon atom.  The R groups have varying sizes, shapes, and chemical activities.  The R group determines the behavior of the different amino acids.


A chain of two or more amino acids is called a peptide, and the bond between the amino acids is called a peptide bond.  A polypeptide is a very long chain of amino acids.  A protein can contain one or more polypeptide chains.  Insulin contains a single chain, while hemoglobin contains four polypeptides.  A protein has a particular shape, which is important to its function.  The shape comes about because R groups of the polypeptide chain(s) can interact with one another in various ways.


A protein's form, therefore its function, can be disrupted by heat or changes in pH.  This disruption is called denaturing of the protein.  Go to the following website and watch the short Flash animation on what happens to the protein in an egg when it is fried.  Take the quiz at the end and note what your answers were.








Carbo formula CH2OA carbohydrate is an organic compound that is composed of atoms of carbon, hydrogen and oxygen in a ratio of 1 carbon atom, 2 hydrogen atoms, and 1 oxygen atom. Some carbohydrates are relatively small molecules, the most important to us is glucose which has 6 carbon atoms. These simple sugars are called monosaccharides.

The primary function of carbohydrates is for short-term energy storage (sugars are for Energy). A secondary function is intermediate-term energy storage (as in starch for plants and glycogen for animals). Other carbohydrates are involved as structural components in cells, such as cellulose which is found in the cell walls of plants.

 Two common Monosaccharides, (single sugars) Glucose and Fructose

Glucose and Fructose are sugarsHooking two monosaccharides together forms a more complex sugar, such as the union of glucose and fructose to give sucrose, or common table sugar. Compounds such as sucrose are called Disaccharides (two sugars). Both monosaccharides and disaccharides are soluble in water.

Larger, more complex carbohydrates are formed by linking shorter units together to form long or very long sugar chains called Polysaccharides. Because of their size, these are often times not soluble in water. Many biologically important compounds such as starches and cellulose are Polysaccharides. Starches are used by plants, and glycogen by animals, to store energy in their numerous carbon-hydrogen bonds, while cellulose is an important compound that adds strength and stiffness to a plant's cell wall.

Sugars are most often found in the form of a "RING". The glucose molecule in the image above and the one in the image below (Glc) are really the same molecule, just arranged differently. The corners of the "stop sign" represent Carbon atoms even thought they are not labeled with a "C" (its chemistry shorthand). To form these rings, the Carbonyl (C=0) Glucose and Galactose are isomersCarbon of the straight-chain form (above) forms a bond with the next to last Carbon in the chain, making the ring.


The image on the left shows two monosaccharides, Glucose and Galactose (Gal). Examine their structure and you will notice there is very little difference. Their molecular formulas, C6H1206, are even the same. Molecules with the same chemical formula, but different molecular structures are called Isomers.

The sugar subunits can be linked by the reaction, dehydration synthesis, to form larger molecules. The disaccharide, Sucrose, is formed from two monosaccharides, Glucose and Fructose.

Sucrose is a DisaccharideThe disaccharide Lactose is a dimer (two subunits) of Glucose and Galactose, the disaccharide Maltose is a dimer of Glucose. Galactose is a sugar found in milk.  Fructose sweetens the taste of fruit.


Large polymers of sugars are called Carbohydrates. Carbohydrates can be 100's of sugars long and either straight or branched. The term Complex Carbohydrate, or sometimes even just Carbohydrate refers to long chains of sugars. Three common types of complex carbo's we will examine are: Starch, Cellulose, and Glycogen. All three are composed only of Glucose. They differ only in the bonding arrangements between the Glucose subunits. Not all complex carbs are composed of glucose alone, many have highly unusual sugars in their chains.

Starch, Cellulose, and Glycogen are polysaccharidesStarch is a long (100's) polymer of Glucose molecules, where all the sugars are oriented in the same direction. Starch is one of the primary sources of calories for humans.

Cellulose is a long (100's) polymer of Glucose molecules. However the orientation of the sugars is a little different. In Cellulose, every other sugar molecule is "upside-down". This small difference in structure makes a big difference in the way we use this molecule.

Glycogen is another Glucose polymer. Glycogen is a stored energy source, found in the Liver and muscles of Humans. Glycogen is different from both Starch and Cellulose in that the Glucose chain is branched or "forked".









Each type of lipid has a slightly different structure, but they all possess a large number of C - H bonds which makes them a primarily non-polar group of molecules. All the C-H bonds also makes them very Energy-rich

There are three different functions for lipids in our bodies:
  • Energy storage
  • Forming the membranes around our cells.
  • Hormones and vitamins

On function for Lipids is that of Energy storage. Lipids contain a lot of calories in a small space. Since Lipids are generally insoluble in polar substances such as water, they are stored in special ways in you body's cells. Lipids can also function as structural components in the cell. Phospholipids are the major building blocks of cell membranes. Lipids are also used as hormones that play roles in regulating our Physiology (metabolism). Most lipids are composed of some sort of fatty acid arrangement. The fatty acids are composed of methylene (or Methyl) groups, and are not water soluble.  They are soluble in a solvent such as alcohol.

Fatty Acids: The lipid building blocks: Saturated Fatty AcidThe common building block for most of the different types of lipids is the fatty acid. Fatty acids are composed of a chain of methylene groups with a Carboxyl functional group at one end.

Saturated and unsaturated fatty acids form different types of lipids.

The methyl chain is the fatty part, the Carboxyl, the acid. The fatty acid chains are usually between 10 and 20 Carbon atoms long. The fatty "tail" is non-polar (Hydrophobic) while the Carboxyl "head" is a little polar (Hydrophillic).

Fatty acids can be saturated (meaning they have as many hydrogens bonded to their carbons as possible) or unsaturated (with one or more double bonds connecting their carbons, hence fewer hydrogens). A fat is a solid at room temperature, while an oil is a liquid under the same conditions. unsaturated Fatty AcidThe fatty acids in oils are mostly unsaturated, while those in fats are mostly saturated.

Compare the fatty acid on the left to the one above. A double bond connects the two, red Carbon atoms. Since Carbon forms four bonds, these Carbon atoms are only bonded to one Hydrogen each. This is not as many as the fatty acid above, so this fatty acid is called unsaturated. (monounsaturated).

The double bond also gives unsaturated fatty acids a bend in the methylene chain. This bend affects the chemical characteristics of unsaturated fatty acids. The straighter, saturated Fatty Acids all line-up very close together and stick to each other. These interactions make them less fluid and more solid (more like Fat). The bent unsaturated Fatty Acids can't get as close together, so they don't stick as much. They are more fluid (more like Oil).

Triglycerides: Energy Storage, Three fatty acids bonded to Glycerol. TriglycerideTriglycerides are Energy-storage molecules. They are formed by connecting three fatty acids (shown in black) to the red part of the molecule on the left, Glycerol. As you can imagine, the three fatty acids together, contain a lot of Energy (aka Calories). Fat has a lot of calories.

The flabby stuff most of us have on certain parts of our bodies is cells filled with triglycerides. In trigylcerides, a fatty acid is joined to each of the three Carbons of Glycerol by Dehydration Synthesis to form a molecule which stores a lot of calories in a small space.





Emulsification of lipids


Some molecules are polar, meaning that they have charged groups or atoms, and some are non-polar, meaning that they have no charged groups or atoms.  A water molecule is polar, and therefore, water is a good solvent for other polar molecules.  When the charged ends of water molecules interact with the charged groups of polar molecules, these polar molecules disperse in water.


Water is not a good solvent for nonpolar molecules like fats.  A fat has no polar groups to interact with water molecules.  An emulsifier, however, can cause a fat to disperse in water.  An emulsifier contains molecules with both polar and nonpolar ends.  When the nonpolar ends interact with the fat and the polar ends interact with the water molecules, the fat disperses in water, and an emulsion results.


Bile salts (emulsifiers found in bile produced by the liver) are used in the digestive tract.