Decomposers Activity 2.2 Directions

Divide the students into pairs, and give each pair the materials that they will need to complete the activity.

• Put posters you intend to use on the wall

Show Slide 3 of 2.2 Molecules Cells Are Made of PPT and point to the copy of the Molecule 11 x 17 Poster on your classroom wall. Ask students to examine the key features of this poster:

• Atoms are represented by differently colored circles. In the Carbon TIME units: carbon is black, oxygen is blue, nitrogen is red, and hydrogen is white.
• Bonds that connect carbon to carbon and carbon to hydrogen bonds are colored yellow. This color represents the chemical energy stored in these bonds. Other types of bonds are not yellow because they do not contain as much stored chemical energy.
• When two or more atoms bond together, this creates a molecule.

Show Slide 4 of the PPT:

• Review some things we know in the left column
• Review unanswered questions in the right column
• This activity focuses on the question in red: “What kinds of molecules are cells made of?”

Have students follow on 2.2 Reading Nutrition Labels Handout as you present Slides 5-18 in the PPT. Each slide points toward parts of the nutrition labels that are also presented on the handout:

• Slide 5 points out that (unlike nutrition labels on most foods) these labels use a standard serving size of 100g.
• Slides 6 and 7 focus on carbohydrates, including how to calculate the amount of starch (total carbohydrate – sugar – fiber)
• Slides 8 and 9 focus on fats, including the atoms in fat molecules (CHO)
• Slides 10 and 11 focus on proteins, including the atoms in protein molecules (CHON)
• Slide 12 points out that all the organic molecules in cells are made primarily of 4 kinds of atoms: CHON. (If you wish to discuss other atoms in organic molecules such as P and S, you could do so later with Slides 21 and 22.)
• Slides 13 and 14 point to cholesterol, vitamins, and minerals: molecules found in cells but always less than 1% of cell mass.
• Slides 15 and 16 focus on how to calculate the amount of water in cells by subtracting the total mass of organic matter from 100g.
• Slides 17 and 18 connect information about calories on food labels with what students have already studied about chemical energy in organic molecules in the Systems and Scale unit. Note that high-energy C-C and C-H bonds are yellow on the illustrations of molecules.

Tell students that now that they have zoomed into food, you will visit the three types of organic molecules more closely. Post three different posters on the wall in your classroom and invite students to examine the difference between them:

• In the Digestion and Biosynthesis of Carbohydrates 11 x 17 Poster , encourage students to notice that large carbohydrates molecules are built of smaller glucose molecules during biosynthesis, and the reverse for digestion.
• In the Digestion and Biosynthesis of Fat 11 x 17 Poster, encourage students to notice that large fat molecules are built of smaller fatty acids and glycerol molecules during biosynthesis, and the reverse for digestion.
• In the Digestion and Biosynthesis of Protein 11 x 17 Poster, encourage students to notice that large protein molecules are built of smaller amino acids during biosynthesis, and the reverse for digestion.

Now that students are somewhat familiar with the molecules in food, have them explore the makeup of other foods. Divide students into pairs to complete 2.2 Food Labels Worksheet.

• Show Slide 19 on the PPT.
• Have pairs of students work together to complete the first row of the worksheet for “beef.”
• Show Slide 20. Check to make sure that all pairs successfully completed the first row.
• Discuss the last question on the worksheet: How are plant and animal cells different? Students should note that plant cells tend to have more carbohydrates and water and less fat and protein than animal cells (with seeds such as peanuts being the exception).

Use Slides 21 and 22 and the Metabolic Pathways Poster to point out that the “whole story” of cell structure and function is much more complicated than they can study in this class:

• Slide 21 points out that large organic molecules—carbohydrates, fats, and proteins—are actually much larger than the molecules illustrated on the slides (too large for illustrations that would show all the atoms).
• Slide 22 points out that there are many more small organic molecules than the ones we have discussed, and that cells have many ways to change one kind of small organic molecule into another.
• Show students the Metabolic Pathways Poster and invite them to look at it more closely when they have time. The poster is still “incomplete” in that it shows only pathways involving small organic molecules. When they study cellular processes such a cellular respiration and photosynthesis, students may enjoy locating them on the poster.

Show slide 25 of the 2.2 Molecules Cells Are Made of PPT.

• Conclusions: What molecules make up food?
• Predictions: How do you think decomposers get molecules for their cells?
• On a sheet of paper or a sticky note, have students individually answer the exit ticket questions. Depending on time, you may have students answer both questions, assign students to answer a particular question, or let students choose one question to answer. Collect and review the answers.
• The conclusions question will provide you with information about what your students are taking away from the activity. Student answers to the conclusions question can be used on the Driving Questions Board (if you are using one). The predictions question allows students to begin thinking about the next activity and allows you to assess their current ideas as you prepare for the next activity. Student answers to the predictions question can be used as a lead into the next activity.