Texting On the Celly

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Objective

The students will be able to describe the function of a cell as a whole and ways parts of cells contribute to the function.

Big Idea

Students investigate structure/function relationships as they test different plant and animal organs for carbohydrates, lipids, proteins, and sugars!

Introduction and Connection to the NGSS and Common Core

In this lesson, students learn about the molecules that are produced in cells and their uses for cells.  Students test for carbohydrates, proteins, and lipids in various plant and animal organs and then analyze their data in order to determine the relationship between the organs and the molecules that are most prevalent in them.

This lesson specifically connects to the following NGSS and Common Core Standards:

MS-LS1-2 Develop and use a model to describe the function of a cell as a whole and ways parts of cells contribute to the function.

MS-LS1-7  Develop a model to describe how food is rearranged through chemical reactions forming new molecules that support growth and/or release energy as this matter moves through an organism.

CCSS.ELA-LITERACY.WHST.6-8.10  Write routinely over extended time frames (time for reflection and revision) and shorter time frames (a single sitting or a day or two) for a range of discipline-specific tasks, purposes, and audiences.

CCSS.ELA-LITERACY.RST.6-8.3  Follow precisely a multistep procedure when carrying out experiments, taking measurements, or performing technical tasks.

Science and Engineering Practices:

Designing and Carrying Out Investigations:  Collect data to produce data to serve as the basis for evidence to answer scientific questions.

Analyze and Interpret Data:  Analyze and interpret data to provide evidence for phenomena. 

Crosscutting Concepts:

Patterns: Observed patterns in nature guide organization and classification and prompt questions about relationships and causes underlying them.

Systems and System Models: A system is an organized group of related objects or components; models can be used for understanding and predicting the behavior of systems.

Connecting to the Essential Question: What are you supposed to learn today?

5 minutes

Begin class by asking, "What are you going to learn today?"  Students should respond by referring to the Essential Question, "How do cells contribute to the function of living organisms?".  This EQ can be referenced both on my front board as well as on their Cells Unit Plan.

Have students get out their Cells Unit Plan.  Explain that their focus of this particular lesson is Skill 3 (I can create a model that shows the relationship between cell structure and function) and Skill 4 (I can identify important materials and processes that are required for cells to function). Have students read the skill and self-assess where they stand in their level of mastery in this skill.  Students rank themselves on a scale of 1 to 4 (4 being mastery). 

As the unit moves forward, I have the students continually self-assess on each skill.  In my class, this will be the students second self-assessment, so they change their scores if they feel that their learning has improved.  Check out the student's unit plan below to see how students update their mastery level with each lesson.

Mini Lesson: Compounds in Cells

25 minutes

I say, "Throughout science, there are concepts that can be applied to every situation.  We have called these "crosscutting concepts".  One of the crosscutting concepts that we have discussed is "Energy and Matter"."  

On the projector, I put up the NGSS unwrapped version of the "Energy and Matter" crosscutting concept:

Energy and Matter: Flows, Cycles, and Conservation: Tracking energy and matter flows, into, out of, and within systems helps one understand their system’s behavior.

  • Matter is conserved because atoms are conserved in physical and chemical processes.
  • Within a natural or designed system, the transfer of energy drives the motion and/or cycling of matter.
  • Energy may take different forms (e.g. energy in fields, thermal energy, energy of motion).
  • The transfer of energy can be tracked as energy flows through a designed or natural system. 

As a class, we break down what the meaning of this concept is and form an idea of what we would be looking for if we were trying to connect to it during a lab or reading.  I explain that as we have gone through units on matter, chemistry, and energy, it is important to apply these concepts across units and find connections in our cells units.  

Next, I read Cell Chemistry aloud to the class.  After every sentence I pause and provide students with time to highlight/circle any word or concept that helps them connect to a the crosscutting concept "Energy and Matter".  (Just so you are aware, I wrote this text and it is definitely written in "my voice".  In addition, it is written from the perspective that the students have covered the chemistry and matter units.)

Reading aloud during this mini lesson is something that I made a deliberate decision to do. As Anne Guignon states as she writes for Education World,  "Reading aloud to children helps them develop and improve literacy skills -- reading, writing, speaking, and listening.....And since children listen on a higher level than they read, listening to other readers stimulates growth and understanding of vocabulary and language patterns."  As middle school teachers it is important to realize that reading aloud is not only for elementary teachers.  All students benefit from hearing adults fluently read scientific text aloud!

After completing the reading, students get into groups of three to four.  The students go around, each sharing a connection to the CCC.  Each student is required to share at least two connections they made to the "Energy and Matter" crosscutting concept (there are a lot to be made in this reading!).  

Texting "Molecules" on the Celly Lab

45 minutes

In this lab, students will test various food types for carbohydrates (sugar and starch), lipids, and proteins.  After testing and collecting data, students analyze the data to determine how the function of the food in the living organism ties to its composition (structure)

Prior to the lab, I prepare put all of the food types that will be tested for carbohydrates, lipids, and proteins in beakers.  I use about 300 mL of each for 4 classes.  I place labeled eyedroppers in each beaker.  I keep all of the beakers together at a central station that students will return to fill their test tubes at with each test.  The food types include:

  • water
  • fish (I use a small package of cheap, thin salmon.  You don't need a lot!!)**
  • apple juice
  • spinach**
  • potato (I only use a half of a potato for four classes)**
  • egg whites

**To prepare the fish, potato, and spinach, cut them up into pieces and add them to a blender with water to liquefy them.  I had an old blender donated to my classroom and I use that every year.  I know you are probably grimacing at the idea of liquefying fish, but it is well worth it for the benefit of this lab.

I set up one station for each group.  This station should include:

  • Set of small test tubes
  • Iodine in Dropper/Dispenser
  • Biuret in Dropper/Dispenser
  • Benedict's Solution in Dropper/Dispenser
  • One small square piece of newspaper
  • Bunsen burner
  • Matches
  • Goggles
  • Heat resistant gloves
  • Test tube holder
  • Test tube brush/clamp

 

Have the students follow the procedure.  Emphasize to follow the directions carefully for safety!

Test for Lipids:  Step 5 is in bold to emphasize this to your students.  Adding the substances to the test tube takes the longest amount of time in this lab.  By saving the "food" in their test tube after the lipid test, they can eliminate having to refill and clean their tubes.

 Procedure:

  1. Put about one eyedropper full of each food in its labeled test tube using an eye dropper.
  2. Put 1 drop of each food onto a piece of newspaper.
  3. Compare the translucence (picture a piece of greasy pizza on a paper) of each food substance on the newspaper.  
  4. In your data chart on your lab sheet, record the amount of translucence.  The items with the most translucence should be ranked a 4 (having a lot of lipids) and the items with no translucence (no lipids) should be ranked 0.
  5. Do not clean out your test tubes!  Use your test tubes to complete the procedure for the test for sugar.

 

The Sugar Test:  Please note that the items in bold are safety precautions.  It is important to follow through with these!

Procedure:

  1. You should have a test tube with each food type left over from the test for lipids. 
  2. Add one eyedropper full of Benedict’s solution to each test tube.
  3. Put on heat resistant gloves.
  4. Using a test tube holder, hold each of the test tubes over a Bunsen Burner. YOU MUST HOLD THE TUBE ABOVE THE RING SO THAT THE FLAME IS NOT DIRECTLY TOUCHING THE TEST TUBE.
  5. If the liquid begins to bubble or boil, remove it from the flame IMMEDIATELY.  
  6. If the food type contains sugar, it will turn colors based on the scale below.
  7. After your test tube has turned color, place it in your test tube rack to cool.  DO NOT TOUCH HOT TEST TUBES WITH YOUR HANDS!  ONLY HANDLE WITH THE TEST TUBE HOLDER!
  8. Observe the results in your test tube and fill in the chart for sugar on your lab sheet.  Your test tubes will be hot and will need to cool down before you clean them out.  See the table below for the color chart:

Check out how this test works:

Completed Test Tube Rack:

Test for Protein:

  1. Put about one eyedropper full of each food in its labeled test tube using an eye dropper.
  2. Add one eyedropper full of Biuret solution to each test tube.  If the item contains protein, it will turn a pinkish purple.  Any test tube that turns purple, record a + in your data table.  Any test tube that does not turn colors, enter a – in your data table.
  3. Empty each test tube in the sink and wash each test tube.

Test for Carbohydrates (Starch):

  1. Put about one eyedropper full of each food in its labeled test tube using an eye dropper.
  2. Add 3 drops of Lugol’s solution (iodine) to each test tube.
  3. If the food type contains carbohydrates, it will turn a blueish-black color.
  4. Observe the results in your test tube and fill in the chart for starch on your lab sheet.  For any food that tests positive for starch, write a + in the data table.  For any that do not test positive, write a - in the data table.
  5. Empty each test tube in the sink and wash each test tube.
  6. Clean up your materials.

 After compiling all of their data, have students complete the lab questions.

Closure

15 minutes

To close, discuss the lab questions as a class.  Below are some pieces of student work that can give you some insight into what the students discuss for each question:

Discussion Question #1:  Identify which food types were the highest for each type of molecule.

Students find that potatoes are the highest in starch, apple juice is the highest in sugar, fish and eggs are the highest in proteins, and egg whites are the highest in lipids.

Discussion Question #2:  Did water contain any of the molecules you tested today?  Why did we choose to test water?

 

Discussion Question #3:  Analyze the data for sugars and starches.  Why did the food types that test high in these molecules?

Students should recognize that carbohydrates are used as immediate and stored energy in cells.  Students discuss how the apple is the fruit of the plant and as the fruit is used in reproduction (seeds), it would need lots of energy.  Also, they explain that potatoes are roots and are food storage organs.  They explain that because they are underground they do not go through photosynthesis so they need to store food as starch.  In addition, they explain that spinach would have sugars as it is a leaf that goes through photosynthesis, producing sugar.  

Discussion Question #3:  Analyze the data for lipids.  Why did the food types that test high in these molecules?

Students explain that the egg grows a new "chicken".  They connect to the idea that lipids are stored energy to the idea that growing a baby would require a lot of energy.

Discussion Question #4:  Analyze the data for protein.  Why did the food types that test high in these molecules?

 

.

Students note that fish had the most protein.  They recognize that fish is a muscle and that proteins are used to growth, strength, and repair (all things that muscles would need).

Discussion Question #5:  We didn't test for nucleic acids in this lab, but they are a common molecule found in cells.  What are nucleic acids?  What is their function in a cell?

Students explain that nucleic acids are found in DNA and that DNA serves as the genetic information in cells.