Macromolecules, part 1

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Objective

Students will understand why the structure of the carbon molecule allows it to form macromolecules that perform vital functions in cells. Students will compare the structure and functions of the 4 biological macromolecules.

Big Idea

The 4 macromolecules perform vital life functions.

Warm-Up

5 minutes

Warm-Up: “When astronomers search for life on other planets, what do you think they typically search for the presence of?” 

This question serves as a good way to quickly gain a sense of students’ thinking and prior knowledge about life and what is needed to sustain life.

Allow students to ponder the question for several seconds before accepting students’ ideas.  Giving students ample time to consider a question allows all learners to have adequate time to consider the question and possible responses.  After a short period of thinking time, allow 2-4 students to share their thoughts.  Make note of what students identify as evidence of life.  Expect students to identify water, or air as evidence of life.  If air is identified as evidence of life, ask students whether all life is aerobic. 

Encourage students to engage in academic discourse for 2-3 minutes before showing a very brief video clip, “Carbon- the element of life” (Discovery Channel).  After viewing the video, ask students to identify what they now know is evidence of life.  Look for students to identify that carbon is found in all things that are or once were living. Introduce the term, “organic compound”.  Compare what students know about the term “organic” as it is used in grocery packaging to what they have just learned about the term “organic”.  Expect the hear that “organic” means grown without pesticides.  Listen to their thoughts and clarify that all produce is “organic” from a scientific perspective.  Clarify that “organic” means something entirely different when it is used for food packaging.  To check for understanding, ask students if all produce is organic or not, as they have just learned from the video clip.  

Introduce New Material

20 minutes

Identify the learning targets for the lesson:

  • Explain why carbon’s structure allows it form molecules essential for life.
  • Identify the functions of the four main biomolecules.
  • Know the properties of basic macromolecules in living organisms.

Learning targets can be for just a day or can reflect a body of knowledge that is expected over a few days of instruction and practice.  Informing students of what they will be expected to know and/or do at the end of the lesson allows them to self-assess throughout the lesson and hopefully, ask questions during the instruction when they are see that they will not be able to meet the learning target by the end of the lesson(s). 

Introduce content related to the four major macromolecules, providing information to students verbally and visually, using a LCD projector.  Instruct students to add information about the four macromolecules to the graphic organizer provided for this lesson.  Encourage students to use markers and highlighters that you have provided as they complete the graphic organizer.

Emphasize that each macromolecule (or polymer) is made of a linkage of sub-units or monomers.  Identify the monomer that is the basic unit of each of the 4 macromolecules.  Use the linking toy from the hydrolysis lesson to reinforce the concept that “monomers make polymers”.  The action of cycling back to the linking toy visual model helps learners recall how the two terms are related. 

While teaching, instruct students to use the Macromolecules Grid to record what is known about each macromolecules:

  • › Elements found in the macromolecule
  • › Functions of the macromolecule
  • › Monomer of the macromolecule (Name and draw)
  • › Examples of the macromolecule

Model how to complete the grid for each macromolecule.  This allows students to compare what they’ve put on their organizers with the information that you indicate is significant and worth documenting on the organizer. Walk around the room during instruction to monitor and ensure that students are adding any information to their graphic organizers as shown on the LCD projector. The two student work graphic organizers show how students were able to create organizers with the same information but are still different in how they chose to use color on the organizers. The use of markers is a good way to engage artistic students in the learning.

During instruction, be sure to address review dehydration synthesis and hydrolysis.  Check to see if students are able to recall and recite the rhyme, “dehydration synthesis _____ polymers and hydrolysis ____ polymers.  Review the terms polymer and monomer by asking students to turn and tell a neighbor the difference between the two terms.  Allow 1-2 students to share their responses with the entire class.  Extend the understanding by asking students to consider whether macromolecules are polymers or monomers.  Emphasis the prefix, macro- and contrast it with the prefix micro-.  Listen for students to recall that poly- means many and macro- means large.  Look for students to make the connection that macromolecules are polymers because polymers are a long chain, which means they are large molecules.  

Guided Practice

10 minutes

Inform students that they will complete a “gizmo” today that will allow them to identify the nutrients in macromolecules, using the Explore Learning technology.  Gizmos are computer simulations that help students see science in action.

Issue the computers so that students have them before you model use of the site for the lesson.  Instruct them to log in and access the main site. 

Note: Explore Learning is an inquiry-based learning system using online simulations.  My school district subscribed to the service a couple of years ago and I have found the lessons to be highly effective in helping my students grasp science concepts.  Sign up for a free trial if you are interested in accessing the resources and student exploration worksheet associated with this lesson. 

Walk around to monitor that all students are on task, able to access the site and log in with their individual user names.  Identify 2-4 students who are skilled computer users and utilize them as a resource to assist other students who are not.  Once it is determined that all students have accessed the site, model how to access the lesson and navigate the gizmo. Instruct students to watch and perform each action that you take, using the computers they have at their desks.

Decide beforehand if you will provide copies of the worksheet or if students will complete and submit electronic worksheets.  Some students work best with hard copies so make the determination in advance of who will need a hard copy and have copies available for those students. If you decide that students can complete the assignment online, model how to download a “word” copy, type their answers onto the worksheet and submit the assignment electronically.

Point out the vocabulary that is associated with the lesson and answer the “Prior Knowledge Question” as a class, taking responses from 1-3 students to develop an answer for the class. This allows you to hear students’ reasoning, as a formative assessment and it allows everyone to start at the same point once you release them to work independently. If students struggle with the question, spiral back and reinforce key concepts before proceeding.

Model 1-2 of the gizmo warm-up activities for the class.  The gizmo warm-up is intended to help students learn how to navigate the controls for the lesson that follows.  As you complete each action, instruct students to use their computers to perform the same action. Release students to complete the warm-up activity as you walk around to ensure that everyone is able to navigate the controls for the lesson.

Independent Practice

25 minutes

Instruct students to work independently or in groups on the computers to complete assigned parts of the Identifying Nutrients gizmo from Explore Learning and the assessment that follows the simulation. Depending on the time, students may not be able to complete all parts of the gizmo so it's important to preview the gizmo to determine which parts are the desired sections for completion.

Instruct students to drop the completed gizmo in Edmodo when they complete the assignment or instruct students to complete a hard copy that you provide.  Based on students’ particular learning needs and abilities, determine which students will submit electronically and which will not.

Note: Edmodo is a great teacher website that allows teachers to load assignments, send reminders and schedule important dates for students and their parent/guardian to access outside of class. Students join a class that is set up by the teacher and are then able to submit assignments directly to the site.  Edmodo also allows students to take quizzes and engage in topic-based chats, as well.

Submission of this assignment electronically serves two purposes.   First, utilizing Edmodo helps students learn how to attach and send files electronically.  By submitting assignments through Edmodo, students learn how to upload files (a skill they will need as they advance in their high school classes). Second, electronic submission of assignments saves a lot of paper and reduces the amount of time needed to make copies of a multi-page document.

Alternatives to electronic submission include, instructing students to send the completed assignment to a designated email address.  If computers are not available in the school setting, instruct students to access a computer outside of class (a local library) to complete the assignment.  A lack of computers in the school setting should not be a deterrent to students’ use of technology.  Encourage students to utilize available resources in the community (libraries) to enhance their technological skills and abilities.

After the completed assignments are received, look for students’ students’ ability to reason and draw correct conclusions.

Close

5 minutes

Engage students in a closing discussion question, “Which macromolecule was not found in the identifying nutrient investigation?”  Look for students to identify that nucleic acids were not a part of the investigation.  Once that it established that nucleic acids are the missing macromolecule, ask students to explain why they are not a part of the investigation.  Look for students to correctly identify that nucleic acids are not found in food but only in DNA and RNA.  Engaging in dialogue with students is a great way to reinforce learning and gain a sense of how much students actually know about a concept.