Activity 5.4 - Explaining How Cows Grow: Biosynthesis (40 min)

Target Student Performance

Students explain how matter moves and changes and how energy changes during biosynthesis in a cow’s cells (connecting macroscopic observations with atomic-molecular models and using the principles of conservation of matter and energy).

Note: This lesson should be taught, regardless of it you taught only Activity 5.1 or both Activity 5.1 and 5.2. However, the language you use and the responses you should expect from your students will be different. Students who did 5.2, molecular modeling, should use the terms “polymers” and “monomers” in their explanations of digestion and biosynthesis, including the names of specific polymers (e.g., proteins, fats and carbohydrates) and monomers (e.g., amino acids, fatty acids, glycerol). Students only did 5.1 should use the terms "large organic molecules" and "small organic molecules" rather than polymers and monomers and use the names of specific large organic molecules (e.g., proteins, fats and carbohydrates) only. Throughout the PPT, you will find both sets of vocabulary.

Resources You Provide

Resources Provided

Recurring Resources


Print one copy of the 5.4 Explanations Tool for Cow Biosynthesis, and the 5.4 How do Animals Grow? Reading (if you choose to use it) for each student. If you are using it, print one copy of the Big Idea Probe: What Happens to the Fat? for each student. Prepare a computer and a projector to display the PPT. Print and hang the Digestion and Biosynthesis 11 x 17 Posters and Metabolic Pathways 11 x 17 Poster. In this activity, your students will need to use the Three Questions Explanation Checklist on the back of the Three Questions Handout. Be sure to have this available to students, and see the notes in the Modifications at the end of the Activity for ideas about how to use it.


1. Use the instructional model to show students where they are in the course of the unit.

  • You may want students to first complete the front side of the Explanations Tool with the graphic organizer and check it together as a class to confirm that the arrows and responses to the prompts are correct. Then, students can use the corrected graphic organizer as a tool to construct their written explanation.
  • After students complete the Animals Matter Tracing Tool, post in the classroom so students can refer back to it
  • Encourage students to explain verbally as well as writing on the Matter Tracing tool
  • Refer to the word wall for questions on Biosynthesis related vocabulary
  • Provide sentence stems to help students answer questions on Big Idea Probe: What Happens to the Fat?

The Three Questions Explanation Checklist on the back of the Three Questions Handout can be used to scaffold students’ explanations in many ways.

  • Students refer to the checklist as they are constructing their explanations.
  • Students use the checklist as they are sharing and revising their explanations with a partner.
  • Students use the checklist to critique and revise their final explanations.
  • Students use the checklist to critique the example explanations for each unit.
  • Students use the checklist to create and/or evaluate a whole-class consensus explanation.

We recommend using this checklist with a gradual release. As students improve in their ability to write their own explanations, they may rely on the checklist less.

Extending the Learning