STUDY GUIDE
Atoms and Molecules for Nutrition (5 pts Extra Credit)
Atoms:
In simple terms, an atom is the smallest chemical building block with a unique identity. That is to say, atoms are different from each other - an atom of carbon is different from an atom of nitrogen. It's made of a nucleus, which is positively charged, and electrons, which are negatively charged.
Opposite charges attract each other and like charges repel (push away), so the nucleus and electrons are attracted to each other. This attraction is critical for chemistry!
Practice Question 1:
Suppose two atoms are next to each other. How would you expect the electrons of one atom to interact with the nucleus of the other? How would you expect the electrons of one atom to interact with the electrons of the other?
Elements:
Differences in the nucleus of an atom can give it different properties.
Which type of atom, or element, an atom is depends on its nucleus. We organize all the possible elements in a periodic table. The shortened version of an element's name shown on the periodic table is its chemical symbol. For example,
Oxygen has the chemical symbol O.
Practice Question 2:
Find a periodic table of elements on the Internet and answer the following questions: a) What is the chemical symbol of phosphorus? b) Which element has the chemical symbol C?

STUDY GUIDE
Atoms and Molecules for Nutrition (5 pts Extra Credit)
Molecules:
Molecules are combinations of atoms that have been stuck together. We write a molecule's formula, a kind of recipe for the molecule, by listing the chemical symbols of the atoms involved, as well as the count of each kind of atom as a subscript (small number to the right of the symbol). If no subscript is given, you can assume that there is only 1 atom of that element. For example, H
2
O = 2 hydrogen atoms and 1 oxygen atom.
Practice Question 3:
Which elements are present in glucose, C
6
H
12
O element are present in one molecule of glucose?
6
? How many atoms of each
Chemical Bonds:
When electrons are shared between two atoms, a force is created that holds molecules together. This attraction is called a bond, and is what holds together, say, the hydrogens and oxygen in a single molecule of H
2
O.
Electrons are generally shared in pairs. For example, if a hydrogen atom is stuck to an oxygen atom, each one shares one electron, making a total of two electrons shared in the O--H bond.
When a single pair of electrons is shared, we say that a single bond has been formed. Sharing two pairs of electrons produces a double bond, and sharing three pairs makes a triple bond. Whether an atom can make single, double, or triple bonds depends on its electrons! For example, oxygen can form 2 bonds, sharing one electron in each bond; it can make two single bonds or one double bond. Carbon can make up to 4 bonds to other atoms, making it useful as a skeleton for biological molecules.
Practice Question 4:
Find an example of a molecule that contains at least one double bond in your text. Name it below, and draw its molecular structure. Then find an example of a molecule that contains only single bonds, and name it as well; you don't need to draw that one.

STUDY GUIDE
Atoms and Molecules for Nutrition (5 pts Extra Credit)
Fatty Acids:
Fatty acids consist of an acidic "head" with the formula COOH, and a long tail of carbon and hydrogen. The long tail is responsible for the inability of oil and water to mix well. Saturated fatty acids have no double bonds between the carbon atoms in the tail. Unsaturated fatty acids have at least one double bond in the tail. Polyunsaturated fatty acids have more than one double bond in the tail.
Omega-3 and omega-6 fatty acids are special kinds of fatty acids where a double bond is 3 or 6 carbons away from the tail, respectively, and are part of cell membranes. While the body can make these acids to some degree, it is helpful to get a moderate amount of them in the diet.
Practice Question 5:
Draw an example of an omega-3 fatty acid below, using the diagram in your book as a guide. Label the omega-3 double bond, as well as the second double bond, and name a food where you might find this fatty acid.