Glucose's Love Letter

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Students will use the RAFT writing style to demonstrate their understanding of condensation or hydrolysis.

Big Idea

RAFTS are a great way to get students writing about science in a creative way.


5 minutes

Warm-Up:  Ask students to select the best answer to this selected response question:

Carbohydrates and lipids have many carbon-hydrogen bonds; therefore, they both

A. Store energy in these bonds

B. Are easily dissolved in water

C. Dissolve only in vinegar

D. Exist only in cells of plants            

This is a good formative assessment question that allows students to synthesize what they've learned about macromolecules in order to answer the question correctly. Ask, “How many of you chose A as the correct answer?” then look around the room to see how many students raise their hands.  Continue this process for answer choices B-D in order to gain a sense of the pervasiveness of misconceptions and errors in thinking among the students. 

Once this is done, ask a student who chose “A” as the answer to explain why A was chosen.  Listen to the response and ask if anyone wants to add more information to what was said.  Again, go through this same process for answers B-D.  Once done, affirm that A is the correct answer.  For responses B-D, explain why each response is incorrect and correct any misconceptions that were heard when students were explaining why they selected B-D as the correct answer.

Content Review

15 minutes

To further activate students’ thinking about the content from the previous lesson, engage students in a jeopardy biochemistry review game.  Select students from the attendance roster to make sure that each student has an opportunity to participate in the game.  Lessen the stress by allowing students to use their notes and send out a “lifeline” to another student for assistance, if needed.  Emphasize that the intent of this review is to allow you to assess how well students understand the content and provide reinforcement of the content, as needed.  Provide explicit behavior expectations for students to follow while the game is played:

  • Everyone participates. No opt-out.
  • It's okay if you don't know the answer.  Don't become frustrated.  Use your notes or seek help from a friend.
  • Encourage one another.

The review of content benefits students because it helps prepare them to work independently during the independent portion of the lesson.

Guided Practice

10 minutes

Ask students how many of them have ever written a love letter or break up letter.  Recall memories of grade school letters written in the typical “Do you love me. Circle yes or no.” Inform students that the assignment consists of using a RAFT to write a love letter to demonstrate their understanding of condensation, hydrolysis and the properties of carbohydrates.

RAFT stands for Role, Audience, Format, and Topic.

Display the RAFT description. Distribute hard copies, as well so that students are able to reference the task as they work.  Explain each part of the RAFT assignment:


You will assume the role of a monomer of glucose.


The audience is a common carbohydrate, either a monomer or polymer (see choices below). 


In learning about dehydration synthesis and hydrolysis, you now know how polymers are formed or broken. Create Glucose’s “love letter” that either is a “hook up” letter with a monomer or a “break up letter” with a polymer. The format you will use is a letter format.  Assume or pretend that glucose is communicating with the audience, as it explains its decision to fall in love and pursue a relationship with a monomer or break up with a polymer.  What is glucose thinking?  How does it feel? How can you describe these things?  What characteristics about the polymer or monomer make glucose attracted or want to break it off? When you assume the first person role of glucose, you will be using words to describe how you would feel when writing a love letter or break-up letter.


Dehydration Synthesis or Hydrolysis

The Writing Task:  Write a love letter or break up letter in which you assume the role of  glucose.  You must decide what you think glucose would feel or think, and then describe it in detail.  Use specific references to characteristics of glucose(simple sugar)  and the polymer or monomer it is either trying to bond with or break with.  You should mention biological concepts including at least one from each of the group of following subjects: (1) hydrolysis or dehydration synthesis, (2) covalent or ionic bonding, (3) water, (4) carbohydrates, (5) polymers, (6) monomers, (7) hydrogen or hydroxide ions. You must also specifically mention at least one polymer by name.  Your response should be at least one 5-7 sentence paragraph written in standard form. 

Model writing 1-2 sentences of a love letter to give students a sense of how to approach the assignment.  “Think aloud” as you model so that students will be able to hear your thinking. 

“Think Aloud” Script example:

“From my research I know that dextrose is a starch, which means it is a complex sugar. How can I associate what I know about dextrose with a break-up letter?  My break up letter can start with, “Dear Dextrose, You are too complex and your starchy ways are getting on my nerves. I want to break up.  Let me check to see if I have used the properties of dextrose to explain why I want to break up.  Yes, I have.”

Independent Practice

25 minutes

Help students grow in their confidence to work independently on this assignment.  Walk around the room and affirm or redirect their ideas as they work.  Expect that some students will struggle with this assignment because it requires them to take a scientific concept and apply it in a non-scientific way.  Encourage students who are struggling to think about what they know about one of the carbohydrates and consider if those characteristics are appealing or not.  Guide students to think about what they would want in a relationship and apply it to the RAFT.

Expect the frustration that some will have and be available to assist them as they work through the thought process that is necessary to write a RAFT.  Remind students that the notes are available as a resource.

The student work samples show that students really had fun with this activity.  They really embraced the idea of writing a letter from the first person perspective of glucose.  Their letters show that students understand the concepts of hydrolysis, condensation and the properties of many carbohydrates.

Student 1 writes about cellulose and how its properties lead to a decision to break -up.  The letter also mentions  a new relationship with sucrose because of its property of feeling energized.  Student work 2 speaks to the properties of sucrose and its detrimental affect on people as the reason for a break-up.  Student work 3 also uses the properties of cellulose as a reason for break-up, citing cellulose for always "keeping a wall between us".  Student work 4 writes about lactose and his inability to no longer tolerate lactose's characteristics.  All four work samples show that students were able to take the scientific concept and apply it to a non-science task.  This type of application indicates mastery of the concepts.

Students enjoy this assignment and are eager to share their letters with the class. Interestingly, most students chose to write a break up letter instead of a make-up letter. I guess it speaks to the nature of most high school relationships.


5 minutes

Allow students to share their work with the class.  Listen for the accuracy of the information in the letters and point specific points out to the class.  The clips of students sharing their work shows that some were more able to use the content specific vocabulary than others.  This is an engaging activity that all students enjoy.