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Content Overview

Lives of Cells: What do they look like? What do they do? Why are cells important?

Students address these and other important questions as they investigate the structures and functions of eukaryotic cells. They begin by observing cells from different tissues under a light microscope to identify common structural features. They then distinguish one cell type from another by differences in their shape and size. They learn how cells of the same type associate to form tissues, how different kinds of tissues associate to form organs, and how organs work together to form systems. Students answer the question, “Why are cells so small?” by exploring what happens to the efficiency of cells when they increase in size, as students investigate the relationship between the surface area of a cell and its volume. Students then learn about essential cell parts and cellular organelles. Using their knowledge of cell parts, they build a three-dimensional (3-D) model of a cell and relate the structure of the cell they choose to its function in the human body. Students then go on to study cell activities and the function of enzymes in facilitating chemical reactions within cells. Students explore the physical properties of DNA by isolating it from thymus tissue. They also build a model of the DNA double helix and then simulate DNA replication. They study the genetic code stored in DNA, how information in genes is transcribed into messenger RNA, and how mRNA is then translated into protein. In the final section of the unit, students consider the health of cells and why it is important in maintaining internal balance, homeostasis, within the body. They explore DNA mutations and distinguish their potential effects when the mutations occur in somatic cells, as compared with mutations that occur in gamete cells. They study genetic diseases, and then they follow the disease process in cystic fibrosis, as an example of how genetic disorders affect the normal functions of cells. Students then learn how normal cells in the body may be transformed into cancer cells by factors both in the environment and from within the body. They compare the differences between the structure and functions of normal cells and cancer cells, and they learn how scientists predict the risks of developing certain types of cancer during a lifetime. Using their knowledge of cancer, students determine ways they can decrease their risk of developing this disease.

How Is This Unit Organized?

Section 1 introduces students to cells as the building blocks of life. Students explore the similarities and differences among cells comprising different tissues. They study how cells are organized and work together to form tissues, organs, and systems. The text and activities help students determine what happens when a cell increases in size, with a focus on the relationship between its surface area and volume.

Section 2 describes cell parts and their functions. Students investigate the composition and function of the cell membrane. Students learn about the properties of the lipid bilayer with its embedded proteins, and relate this structure to its functions as a semipermeable membrane that allows some substances to pass through it, while others are blocked. Students study the fluid movement of proteins within the bilayer. They then apply their knowledge of cell parts in building a three-dimensional model of a cell.

Section 3 explores important activities of cells including cellular respiration, diffusion, osmosis, active transport, and cell division. Students investigate the role and action of enzymes and factors that affect their functions in the cell. They simulate and compare the process of mitosis in somatic cells with the process of meiosis, which produces gamete cells.

Section 4 introduces students to DNA and the genetic code. They explore the physical properties of DNA isolated from thymus tissue and then build a paper model of the DNA double helix and use it to simulate the replication of DNA. Students study the organization of the genetic information stored in the DNA molecule and simulate the transcription of a gene into an mRNA molecule and its translation into protein at the ribosomes.

Section 5 explores the important function of cells in maintaining internal balance, or homeostasis. Students consider factors within the body and in the environment that affect the health of cells. Students compare the appearance of cells in normal and diseased tissue. They learn about mutations in the DNA molecule and their potential effects in somatic cells and in gamete cells. Cystic fibrosis is studied as an example of an inherited genetic disorder. Students explore cancer and its effects on cells. They consider how scientists predict the risk for developing certain types of cancer, and use this information to determine ways to reduce their risk of developing this disease.

Why Teach This Unit?

There are thousands of genetic disorders that affect the function of cells in the human body.

For example, cystic fibrosis is an inherited genetic disorder that affects the normal function of cells in the lungs and other organs. Although treatments are far better today and more innovative treatments are under development, most patients with cystic fibrosis do not live beyond their twenties. The Cystic Fibrosis Foundation estimates that the disease occurs in 1 in 3,300 live births in the United States. One in four deaths in the United States is due to some form of cancer (American Cancer Society, 1998).

The National Cancer Institute estimates the overall annual costs of cancer to be more than $107 billion (1998).

Due to research on cells, the knowledge generated, and its application in the treatment, 4 out of 10 new cancer patients are expected to be alive 5 years after diagnosis (American Cancer Society, 1998).

Students can apply their knowledge of the structure and functions of cells and factors that affect the health of cells to issues of how to reduce their risks of developing certain types of cancer (by not smoking, eating a low-fat diet, and reducing exposure to toxic chemicals in the environment and to all types of air pollution).

Unit Activities and Key Ideas
Section Key Ideas Activity

1. Building Blocks of Life

What are cells?

  • Cells are the basic unit of life, each with a specific purpose.
  • Cells, tissues, organs, and systems work together to form the structures and perform the functions of the human body.
  • Cells are small, thus maintaining a vast surface area per unit volume to enhance cell efficiency.

Mini Activity: Using a Microscope to See Cells

Mini Activity: Relative Size of a Cell

Mini Activity: Imagine a One-celled Human

Activity 1-1: Why Are Cells Small?

Mini Activity: How Changes in Surface Area and Volume Affect Cells with Different Shapes

2. Cell Parts and Their Functions

What is the structure of cells?

  • Cell parts and organelles are responsible for the specific functions of eukaryotic cells.
  • The cell membrane is composed of a bilayer of lipids and proteins arranged in an orderly manner.
  • The substances that go into or out of a cell are determined by the structure of the cell membrane.

Mini Activity: A Drawing or Model of a Cell Membrane

Mini Activity: Soap Bubbles

Mini Activity: What Does Each Part of a Cell Do?

Activity 2-1: Making a Cell Model

3. Cell Activities

What are some cell functions?

  • The life of a cell depends on the activities that take place within it and also on the environment surrounding it.
  • Enzymes help chemical reactions take place inside the cell. They help build products, make copies of molecules, and carry out cell functions efficiently.
  • The selectively permeable cell membrane allows water to pass through it, but not large molecules dissolved in water.
  • Passive and active transport are the processes by which substances move in and out of the cell.
  • Cellular respiration requires oxygen and produces ATP, the energy needed for the cell to do its work.
  • Cell division is one of the important events of the cell cycle.

Activity 3-1: Catalysts and Enzymes in Your Life

Mini Activity: Transport of Nutrients: Exploring Diffusion

Activity 3-2: Cell Division-Double or Nothing

Mini Activity: Mitosis in Action

Enrichment 3-1: Exploring Osmosis

4. DNA and the Genetic Code

How important is DNA in the functioning of a cell?

  • The genetic information contained in cells is stored in DNA molecules and copied accurately so that each daughter cell receives the same information.
  • The genetic code is represented by sequences of triplet nucleotides in the DNA molecules.
  • Different cell types in your body use or express different portions of your DNA called genes. Genes code for the production of specific proteins in the cell.
  • The transcription of mRNA and its translation at the ribosomes are the processes involved in making proteins.

Activity 4-1: Removing DNA from Thymus Cells

Activity 4-2: Building and Using a DNA Model

Mini Activity: Coding

Mini Activity: Building a Protein Model

Enrichment 4-1: Making Protein

5. The Health of Cells

In what ways does your general health depend on the health of your cells?

  • Cells have important functions in maintaining homeostasis, or internal balance, within the body. Factors that affect the functions of cells come from within the body and from the external environment.
  • A permanent change in the DNA of a cell is called a mutation.
  • Cancer cells are different from normal cells in how they recognize other cell types, reproduce, move, and respond to chemical signals.
  • Individuals can lower their risk of developing certain kinds of cancer by limiting their exposure to specific cancer-causing agents and making wise lifestyle choices.
Activity 5-1: Cells Gone Awry

Teacher's Guide Overview

This Lives of Cells unit is built around a variety of student activities. Text material can be used to introduce, reinforce, and extend the concepts developed in the activities. The activities are the foundation of this unit, so the unit's success depends on students' involvement in the activities. Embedded activities are interrelated, since the concepts developed in one may be applied in another.

Section Planning

For each section, you'll find extensive advance planning for the student activities and the section topic. Key ideas, section objectives, background information, suggestions for introducing activities, and the materials needed for each activity are listed on the Section Planning page. Review this information ahead of time to ensure that materials for each activity are available when you need them.

Support for Embedded Activities

Embedded activities are those activities contained or “embedded” in the student edition. Procedures for each embedded activity are contained in the student edition. In the Teacher's Guide, you'll find activity planning information, activity assessment, and student reproducible pages for each embedded activity.

Enrichment Activities

Enrichment activities are activities found in the Teacher's Guide only. These activities are designed to extend and enrich students' learning experiences. Complete Enrichment activities, including Teacher Activity Notes and student procedures and reproducible pages, are located at the end of each appropriate section of the Teacher's Guide.

GroupWork Activities

Learning science is a process that is both individual and social. Students in science classrooms often need to interact with their peers to develop a knowledge of scientific concepts and ideas, just as researchers, engineers, mathematicians, and physicians work in teams to answer questions and solve problems. The GroupWork activities of the HumBio Curriculum for the Middle Grades have been developed to foster a collaborative environment for groups of students. Students plan experiments, collect and review data, ask questions and offer solutions, use data to explain and justify their arguments, discuss ideas and negotiate conflicting interpretations, summarize and present findings, and explore the societal implications of the scientific enterprise. In short, GroupWork activities provide an environment in which students are “doing science” as a team.

For more information, refer to “Using GroupWork Activities” on TE page 85. The specific GroupWork activities for this unit can be found on TE pages 88-115.

Projects

The research and action projects in HumBio are varied and provide students with time to explore a particular topic in depth. With Projects, students have the opportunity to take a position based on knowledge gained through research, debate an issue, and devise a plan of action. In this way, students can apply what they are learning to larger issues in the world around them.

Projects for this unit include

  • Research Questions
  • Cell Models

Assessment Overview

Within each section of the unit there are suggestions for assessment that can be used individually or in combination to develop a complete assessment package. The list below describes the variety of assessment tools provided.

Apply Your Knowledge questions appear throughout each section. They can be used as homework assignments and as ways to initiate a class discussion. These questions are designed to assess

  • communication skills
  • depth of thought and preparation
  • problem-solving skills
  • ability to apply concepts to related or big ideas
  • how well students relate their new knowledge to their different problems

What Do You Think?

These questions appear in each section. They provide students with opportunities to think and write about the concepts they are learning in a larger context. You can use these questions to assess

  • writing skills
  • problem-solving abilities
  • creativity and depth of thought
  • the ability to analyze and summarize

Journal Writing prompts are suggested throughout the unit. These prompts provide opportunities for students to write critically and creatively about concepts and issues. The writing products can be used to assess

  • writing skills
  • depth of thought
  • the ability to explain and expand and on concepts and issues

Review Questions

Review Questions are located at the end of each section. These questions can be used for written responses or as the basis for class discussion. These questions are designed to assess content knowledge and whether students can explain the concepts explored in the section.

Activity-Based Assessment

Inquiry-based student-centered activities are the foundation of the Human Biology program. The unit is rich with relevant and exciting activities that introduce, support, or reinforce concepts students are exploring. Within the Teacher's Guide, you'll find extensive teacher information, including assessment strategies, for each type of activity:

  • Embedded Activities
  • Enrichment Activities
  • Mini Activities
  • GroupWork
  • Projects

Building a Protein Model Collect 50 pop beads or linker cubes. If possible, select pop beads having 20 different colors to represent the 20 different amino acids. Use any combination of colored pop beads to make a chain of 50 beads. Check with your classmates to see if anyone else has the same sequence of colored beads. What does this tell you about the number of possible proteins that can be made from 20 different amino acids?

You can use students' products to assess their progress. These products include models, simulations, observations and reports of laboratory investigations, role plays, written responses to questions and written observations, student-designed explorations and procedures, poster presentations, and classroom presentations.

PORTFOLIO ASSESSMENT

You may want to have each student develop a portfolio for the unit. Portfolio assessment is an excellent way to assess the student as he or she progresses through the unit. Although there are many opportunities to select a variety of students' products, the following list shows one possible assessment portfolio for this unit:

  • Written responses to three What Do You Think? questions
  • An analysis of the student's two favorite Activities and how those activities helped the student learn an important concept
  • Written responses to one Apply Your Knowledge question from each section
  • Reports from three laboratory investigations such as

Activity 3-1: Catalysts and Enzymes in Your Life

Activity 4-1: Removing DNA from Thymus Cells

Activity 5-1: Cells Gone Awry

  • Two examples of constructing a model from the following:

Activity 2-1: Making a Cell Model

Activity 4-2: Building and Using a DNA Model

  • Two examples of calculations from the following:

Activity 1-1: Why Are Cells Small?

Mini Activity: How Changes in Surface Area and Volume Affect Cells with Different Shapes

Getting Started

Keep Students Interested. Encourage students to read the text: It is the story line that ties all of the content together. Every effort has been made to make the text interesting to students and appropriate to their reading level. Text material can be used to introduce, reinforce, and extend the concepts addressed within the activities.

The success of the unit depends on the completion of at least the Embedded activities. And keep in mind that some activities are related since the data obtained in one may be used in another.

Plan Ahead. The unit is activity-based, and you can select the activities that will best meet your class' needs. The activities are listed in the Unit Matrix on page xiv and in the Activity Index on page 122. Mini Activities are shorter and can be done with minimal teacher input; they are located in the margin of the student edition. The Embedded activities in the student text are investigations that require some planning and setup time; these are the essential activities within the unit. Other investigations called Enrichment activities are located at the end of each section in the Teacher's Guide. Enrichment activities expand student knowledge of the concepts explored in the given section.

A variety of projects were designed to extend the content of the unit. These include ongoing class projects, school projects, and/or community projects. Projects are located at the end of the Teacher's Guide, beginning on page 116.

Customize the Unit. Each section of this unit builds upon knowledge gained in the previous sections. Teaching timelines are provided on TE pages xxii-xxiii. The first timeline on TE page xxii demonstrates how to complete this unit within a threeweek schedule. The timeline on TE page xxiii demonstrates how to complete this unit within a five-week schedule. Both of these timelines highlight the essential activities. If your class has time to study the unit over a longer period of time, many additional activities are available.

Allow Time for Projects. Consider having students start projects at the beginning of the unit and then prepare those projects for presentation as a culminating event.

Use Current Events. Ask students to bring in newspaper and magazine articles that relate to what they are studying each week. Relating the unit content to current events helps students see that what they are doing in class is, in fact, relevant to their lives outside of school. Students can use current events to make group scrapbooks, bulletin boards, and posters or to develop class presentations.

Make a “Question Box” Available. Have students write down questions they have about what they are investigating and put them in the box. At appropriate times select questions and read them to the class to generate discussion. These questions can also be used to initiate class research projects.

Use a Variety of Resources. We encourage you and your students to use a wide variety of sources for information. The activities provide rich opportunities for students to explore a variety of concepts. The more students incorporate information from resources outside the classroom, the richer their learning experiences will be. Use computer services for gathering student and teacher information, for networking with students in different schools and with community resources, and for contacting experts in the field under study. A list of resources can be found on page 119 of this Teacher's Guide.

Make Career Connections. Encourage students to investigate careers related to the content of the unit. Invite scientists, physicians, and technologists working in the field to come to your classroom to discuss career opportunities, their research, and specific topics of interest.

Plan for Field Trips. Field trips to local hospitals, industrial sites, or universities need, of course, to be arranged well in advance. Contact the public affairs offices of these institutions for assistance.

Address Health Concerns. Be aware of any special health problems your students may have. Some students may have health conditions that would make it uncomfortable for them to participate in certain activities, such as those that require exercise or that relate directly to their particular health problems. For students unable to participate fully in these activities you may wish to create an alternative assignment or have them use data from another group. If the class is appropriately prepared, the affected students may want to share information about their special circumstances with the class in order to increase empathy and knowledge of all students.

Connect with Other HumBio Units. The units covering human physiological systems, cell biology, and genetics are related. There are many opportunities to make connections among the concepts taught in these units. Similarly, the three units covering the biological, behavioral, and social aspects of adolescent development can be taught in sequence.

Connect with Other Disciplines. The interdisciplinary web provided is a guide for planning if your school uses an interdisciplinary team approach. The Social Studies web classifies the unit's activities and projects by related discipline-language arts, math, social studies, physical education, health/nutrition, and visual/performing arts, and science. For interdisciplinary planning, schedule meetings with your team early. You are encouraged to tap the talents and interests of your team members as well as of your unique school and community resources in developing other suitable activities for this unit.

Connect with the Home. Give special attention to the unit activities as a means of involving family and community members. Also, encourage your students to take selected Apply Your Knowledge questions and Mini Activities home for further exploration.

Teaching Timelines

You can use these timelines as a place to start in designing your own timelines, or you can use them as they are laid out. If you're planning your own timeline, consider the inclusion of the Embedded activities first. The “Embedded activities” are included in the student edition. The Enrichment activities, GroupWork activities, and Projects can then be included, depending on your time restrictions. The timelines are guides that can vary if some activities are done at home or in other classes in addition to science.

Given your time constraints, it may not be possible to do all the activities shown on these timelines. If you need to remove activities, be careful not to remove any activities critical to the content of the unit. You may want to divide the activities among interdisciplinary members of your teaching team.

Page references in this chart refer to the student edition, except when Enrichments are suggested. The page references for Enrichments refer to this Teacher's Guide.

Option 1: Three Week Timeline
Monday Tuesday Wednesday Thursday Friday
Week 1

Introduce the unit

Introduce Section 1

Assign Mini Activity: Relative Size of a Cell

Complete Mini Activity: Using a Microscope to See Cells

Assign Mini Activity: Imagine a One-called Human

Complete Activity 1-1: Why Are Cells Small?

Mini Activity: How changes in Surface Area and Volume Affect Cells with Different Shapes

Review and Summarize Section 1

Introduce Section 2

Complete Mini Activity: Soap Bubbles

Complete Mini Activity: A Drawing or Model of a Cell Membrane

Complete Mini Activity: What Does Each Part of a Cell Do?
Week 2

Assign Activity 2-1: Making a Cell Model (for a home project)

Summarize and Review Section 2

Introduce Section 3

Complete Activity 3-1: Catalysts and Enzymes in Your Life

Complete Mini Activity: Transport of Nutrients: Exploring Diffusion Complete Activity 3-2: Cell Division-Double or Nothing

Complete Mini Activity: Mitosis in Action

Review and Summarize Section 3

Week 3

Introduce Section 4

Complete Activity 4-1: Removing DNA from Thymus Cells

Introduce and begin Activity 4-2: Building and Using a DNA Model

Finish as homework

Discuss and explain protein synthesis: transcription and translation

Assign Mini Activity: Coding (for homework)

Assign Mini Activity: Building a Protein Model (for homework)

Introduce Section 5

Complete Activity 5-1: Cells Gone Awry

Unit Review

Unit Assessment the following week

Option 2: Five Week Timeline
Monday Tuesday Wednesday Thursday Friday
Week 1

Introduce the unit

Introduce Section 1

Assign Mini Activity: Relative Size of a Cell

Complete Mini Activity: Using a Microscope to See Cells

Assign Mini Activity: Imagine a One-celled Human

Introduce Activity 1-1: Why Are Cells Small?

Complete Activity 1-1

Mini Activity: How Changes in Surface Area and Volume Affect Cells with Different Shapes

Review Section 1

Introduce Section 2

Complete Mini Activity: Soap Bubbles

Complete Mini Activity: A Drawing or Model of a Cell Membrane

Week 2 Complete Mini Activity: What Does Each Part of a Cell Do? Begin Activity 2-1: Making a Cell Model, if it is being done in class

Continue work on Activity 2-1-due in one week

Review Section 2

Quiz: on Sections 1 and 2

Introduce Section 3

Complete Activity 3-1: Catalysts and Enzymes in Your Life

Week 3 Complete Mini Activity: Transport of Nutrients: Exploring Diffusion Complete Enrichment 3-1: Exploring Osmosis Complete Activity 3-2: Cell Division-Double or Nothing

Complete Mini Activity: Mitosis in Action

Review Section 3

Cell models due

Section 3 Quiz

Week 4

Introduce Section 4

Complete Activity 4-1: Removing DNA from Thymus Cells

Introduce and begin Activity 4-2: Building and Using a DNA Model Complete Activity 4-2. Discuss and explain protein synthesis, transcription, translation. Assign Mini Activity: Coding Assign Mini Activity: Building a Protein Model
Week 5 Complete Enrichment 4-1: Making Protein

Review and Assess Section 4

Introduce Section 5

Complete Activity 5-1: Cells Gone Awry Unit Wrap-up/Review Unit Unit Assessment

Safety for Teachers

  • Always perform an experiment or demonstration on your own before allowing students to perform the activity. Look for possible hazards. Alert students to possible dangers. Safety instructions should be given each time an experiment is begun.
  • Wear glasses and not contact lenses. Make sure you and your students wear safety goggles in the lab when performing any experiments.
  • Do not tolerate horseplay or practical jokes of any kind.
  • Do not allow students to perform any unauthorized experiments.
  • Never use mouth suction in filling pipettes with chemical reagents.
  • Never “force” glass tubing into rubber stoppers.
  • Use equipment that is heat resistant.
  • Set good safety examples when conducting demonstrations and experiments.
  • Turn off all hot plates and open burners when they are not in use and when leaving the lab.
  • When students are working with open flames, remind them to tie back long hair and to be aware of loose clothing in order to avoid contact with flames.
  • Make sure you and your students know the location of and how to use fire extinguishers, eyewash fountains, safety showers, fire blankets, and first-aid kits.
  • Students and student aides should be fully aware of potential hazards and know how to deal with accidents. Establish and educate students on first-aid procedures.
  • Teach students the safety precautions regarding the use of electricity in everyday situations. Make sure students understand that the human body is a conductor of electricity. Never handle electrical equipment with wet hands or when standing in damp areas. Never overload electrical circuits. Use 3-prong service outlets.
  • Make sure that electrical equipment is properly grounded. A ground-fault circuit breaker is desirable for all laboratory AC circuits. A master switch to cut off electricity to all stations is desirable for all laboratory AC circuits.
  • Make sure you and your students are familiar with how to leave the lab safely in an emergency. Be sure you know a safe exit route in the event of a fire or an explosion.

For Student Safety

Safety in the Classroom

  • Wear safety goggles in the lab when performing any experiments. Tie back long hair and tuck in loose clothing while performing experiments, especially when working near or with an open flame.
  • Never eat or drink anything while working in the science classroom. Only lab manuals, notebooks, and writing instruments should be in the work area.
  • Do not taste any chemicals for any reason, including identification.
  • Carefully dispose of waste materials as instructed by your teacher. Wash your hands thoroughly.
  • Do not use cracked, chipped, or deeply scratched glassware, and never handle broken glass with your bare hands.
  • Lubricate glass tubing and thermometers with water or glycerin before inserting them into a rubber stopper. Do not apply farce when inserting or removing a stopper from glassware while using a twisting motion.
  • Allow hot glass to cool before touching it. Hot glass shows no visible signs of its temperature and can cause painful burns. Do not allow the open end of a heated test tube to be pointed toward another person.
  • Do not use reflected sunlight for illuminating microscopes. Reflected sunlight can damage your eyes.
  • Tell your teacher if you have any medical problems that may affect your safety in doing lab work. These problems may include allergies, asthma, sensitivity to certain chemicals, epilepsy, or any heart condition.
  • Report all accidents and problems to your teacher immediately.

HANDLING DISSECTING INSTRUMENTS and PRESERVED SPECIMENS

  • Preserved specimens showing signs of decay should not be used for lab observation or dissection. Alert your teacher to any problem with the specimen.
  • Dissecting instruments, such as scissors and scalpels, are sharp. Use a cutting motion directed away from yourself and your lab partner.
  • Be sure the specimen is pinned down firmly in a dissecting tray before starting a dissection.
  • In most cases, very little force is necessary for making incisions. Excess force can damage delicate, preserved tissues.
  • Do not touch your eyes while handling preserved specimens. First, wash your hands thoroughly with warm water and soap. Also wash your hands thoroughly with warm water and soap when you are finished with the dissection.

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6 , 7 , 8

Date Created:

Feb 23, 2012

Last Modified:

Apr 29, 2014
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