- Carbo, Lipid & Proteins PreLab
You may want to install the Chime plug in. The Chime plug-in allows you to view molecules in 3 dimension. Download the plug-in, follow the instructions, and away you go. The right mouse button is very important in manipulating the Chime 3-D structures, play with it to see the molecules in different ways! Viewing the molecules in 3-D is NOT required for this PreLab

Proteins

You have heard before that the four types of biological macromolecules are all polymers. Carbohydrates are sugar polymers. We built lipids from fatty acids, phosphate groups, and glycerol. Now we come to proteins, which are also polymeric. The subunits which make-up Proteins are Amino Acids. The amino acids are joined together by a dehydration synthesis reaction to form chains, which are hundreds of amino acids long; called proteins.

Proteins function as enzymes or as structural units in cells. They do most of the "work" in a cell. Almost all of the exciting stuff; metabolism, memory, hormone action, and movement involves proteins.

amino acidAmino acids are aptly named. See which functional groups you recognize as part of this amino acid. You will also notice there is an R as part of this molecule. There is no element with the abbreviation, R. This letter is used as a sort of chemical variable, like X in math. At this position (the R-group) in an amino acid, different functional groups can be present. There are twenty different types of amino acids found in proteins. Each has a different R-group.

As we just said.... there are twenty different types of amino acids found in proteins: The eight essential amino acids are shown in bold in the table below. Essential amino acids must be acquired in the diet; whereas nonessential amino acids can be synthesized by the body. Complete dietary proteins contain both the essential and nonessential amino acids. Incomplete proteins are missing one or more amino acids. As you eat them, proteins are digested and degraded by enzymes in the stomach. This process takes the proteins you consume and coverts them into the component amino acids by breaking the covalent bonds which connect the subunits of the proteins. The amino acids are then "reused" to make new, different proteins

The links below will show the structure of each amino acid in 3-D, but you must have the CHIME plug-in installed. Viewing the molecules in 3-D is NOT required for this PreLab.

alanine cysteine histidine methionine threonine
arginine glutamic acid isoleucine phenyalanine tryptophan
asparagine glutamine leucine proline tyrosine
aspartic acid glycine lysine serine valine

The 20 types of amino acids differ only at the R position.


Biuret test for Protein

Questions: Answer the questions below, then submit them along with your name and Lab instructor.

1. Glucose in the urine, glycosuria, can be an indicator of Diabetes. Which test would you use to test suspect urine for the presence of sugars?

Benedict's
IKI
Biuret
Sudan IV

2. In the presence of monosaccharides IKI will turn what color?

Blue/Black
Orange/Red
Yellow
It won't change

3. In the Lipid test experiment, which sample was the positive control?

Oil
Water
Food 1
Food 3
Food 5

4. During the Biuret test for proteins, there was a tube labeled P, what do you think P stands for? What was in the tube labelled P?

5. Benedict's solution is a test for the presence of reducing sugars. Which of the following is NOT a reducing sugar?

Starch
Maltose
Glucose
Lactose

6. Carbohydrates are particularly important in biological systems as...?

A. Enzymes
B. Sources of energy
C. Structural components of cells
D. A & B
E. B & C
F. A & C

7. Which macromolecule has the most calories per gram; Carbohydrates or Lipids? How can you tell by look at the molecule?

8. The eight essential amino acids are called essential because...?

You must learn them to pass Biology.
They are found in proteins more often than the non-essential amino acids.
They form the "essence" of proteins.
Their presence inhibits bacterial growth.
Humans must be acquire them in their diet, because we can not synthesize them.

9. A student has just been found poisoned at DUC. In his teeth you find a small piece of food which looks like either a small piece of cooked potato or apple. The piece of food could been from the poisoned meal and we want to know which he ate. Which of the below Bio 121 Lab 2 tests could be used to distinguish between an Apple (loaded with Fructose) and a potato (loaded with Starch)?

Biuret
IKI
Carbonyl
Sudan IV

Name: (*teaching moment) When submitting electronic forms, especially those for credit, be sure to use your actual first and last name; not just your first name and not your "nickname". The name you submit should match that on your course registration, and therefore the gradebook. Thanks.
Section:

Submit your answers to obtain a printable receipt. Be sure to select your section from the drop-down box.