Name ________________________ Biology 165 Lab Activity Sheet 2 Macromolecules: Carbohydrates and Lipids The Structure of Carbohydrates (sugars) and Lipids (fats) 1. Using the octet rule, fill in the following table with the number of covalent bonds each atom can make in a molecular compound based on its atomic number in parentheses: CARBON (6) OXYGEN (8) HYDROGEN (1)

STUDENT ACTIVITIES: Sharing a model kit with your table, work together to examine the structures of glucose sugar and lipids (triglyceride and phospholipid). A. MODELING GLUCOSE (C6H12O6) - A MONOSACCHARIDE: Using the color codes below, build a model of glucose. Model Color Codes:   

BLACK - Carbon RED - Oxygen WHITE- Hydrogen

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Instructor initials _________

GLUCOSE CONTINUED: 1. ANSWER THE FOLLOWING QUESTIONS: a. Observe the arrangement of carbon (C) , oxygen (O), and hydrogen (H) atoms in your glucose model. b. On your model, do all atoms appear to make their maximum number of covalent bonds? YES

NO

c. Recall how partial charges develop on water molecules. Are there any areas in the

glucose model where partial charges should develop? YES

NO

d. Glucose is a polar molecule. Label the atoms on the image above that exhibit partial positive (δ+) and/or partial negative (δ‒) charges.

B. MODELING A LIPID (TRIGLYCERIDE) MOLECULE: A triglyceride, or fat, molecule consists of three chains of carbon atoms with oxygen only on one end. Each chain is a fatty acid. The three are connected through a molecule called glycerol. Model Color Codes:   

BLACK - Carbon RED - Oxygen WHITE- Hydrogen

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Procedure: a. On the figure above, circle the three carbon atoms of the glycerol. b. Construct your model so that it contains three fatty acid chains. Instructor initials _____  

Note: the exact length of the fatty acid chains may vary among different groups’ models, there is no “absolute” fatty acid length. Each model, however, should contain three fatty acids of the same length decided by the group. Note the location of hydrogen atoms on the image and model. In figures, such as the one above, the location of hydrogen atoms is often depicted as an emptyended stem.

1. ANSWER THE FOLLOWING QUESTIONS: a. Consider how partial charges develop on water molecules – are there any areas in the fat molecule where partial charges should develop? YES

NO

b. How does this affect the behavior of oils in water? c. Draw a box around the areas on the figure where oxygen atoms form double covalent bonds. Find these on the model. c. Draw an arrow on the figure to indicate where a double covalent bond occurs between carbon atoms. d. Compare the fatty acids with no carbon double covalent bonds to the fatty acid with the double covalent bond. How are the shapes of the fatty acid molecules different?

e. How many hydrogens are attached to each of the carbons in a double bond? _______ f. How many hydrogens are attached to each of the carbons elsewhere in the chain? _______ g. Triglycerides with fatty acid chains that have no double bonds between carbons are referred to as saturated fats. The presence of double bonds between carbons causes the triglyceride to be an unsaturated fat. 1. On the triglyceride figure above, circle and label the fatty acids that are saturated and unsaturated. 3

C. MODELING A PHOSPHOLIPID: The phospholipid is the primary molecule of all cell membranes. It is based on the triglyceride, but has a phosphate group in place of the third fatty acid. Model Color Codes: a. b. c. d. e.

BLACK - Carbon RED - Oxygen WHITE- Hydrogen PURPLE - Phosphorus BLUE - Nitrogen

Procedure: 1. To convert a triglyceride into a phospholipid, remove the third fatty acid from the glycerol molecule. 2. Attach the nitrogen/phosphorus “head” as depicted in the image. 3. Phosphorus (P) attached to four oxygen molecules (O) is known as a “phosphate group” and has the formula PO4―. The negative charge indicates an extra electron; it is on the oxygen atom lacking one of its covalent bonds. Draw a (–) symbol on this oxygen at right. Instructor initials: ______

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4. ANSWER THE FOLLOWING QUESTIONS ABOUT PHOSPHOLIPIDS: a. The phospholipid “head” is considered (circle one): POLAR NONPOLAR b. The fatty acid “tails” are the same as in a triglyceride. They are considered: POLAR NONPOLAR c. Which do you predict will interact with water molecules, the “head” or the “tails”?

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