Time Required: 6 Class Periods

Cell Structure

Subject: Science

Grade: 6

Time Required: 6 Class Periods

Content TEKS and Clarifiers:
6.10 The student knows the relationship between structure and function in living systems. The student is expected to:
(A) differentiate between structure and function;
(B) determine that all organisms are composed of cells that carry on functions to sustain life
Educational Objective:
What the student must know:
All living things are made up of cells. Cells contain different parts that have specific jobs or functions, including genetic material. Plant and animal cells have many common structures, but only plant cells have chloroplasts and cell walls.
What the student must do:
Use a microscope to observe different types of cells, and complete labeled cell drawings showing the parts of cells. Compare and differentiate between animal and plant cells using aVenn diagram.Represent cells and cell parts by creating a 3-dimensional model and an analogy of cell parts and functions.
More Information:
/ For more information see the TRIAND Resources icon for this SE.
Vocabulary:
/ Cell
Cell wall
Cell membrane
Nucleus
Mitochondria
Chloroplasts
Vacuoles
Cytoplasm
NOTE: Students should be able to define vocabulary words from their learning experiences. More detailed information is found in the teacher background section.
/ For ideas on teaching vocabulary, refer to the TRIAND resources icon to select District Strategies: Verbal/Visual, Automaticity, etc.
Procedures:

ENGAGE

Ask students how many grains of sand they think might be on the beach in Galveston.
Tell students that humans are made of billions of tiny parts just as the beach is made up of many tiny grains of sand.
Write the word cell on the board.
Ask students if they recognize the word cell, and what it might mean. (Accept all responses for now.)
Pass out microscopes, microscope slides and paper thin slices of cork (The cork must be precut by the teacher prior to class.)
Tell students to make a dry slide of the cork and to look at the cork under the microscope. (Remind students to start with low power and then go to medium and high power.)
Ask students what they see. (They should see little areas that look like little rooms surrounded by thin walls – any description is okay.)
Explain to students that Robert Hooke, an English scientist, was one of the first people to see cells under a microscope. He called them cells because they looked like little rooms in a prison or a monastary. (Explain to students that rooms in a prison or a monastary are referred to as cells if they have any questions about the name.)
Ask students why they think the cells might be empty. (The cork is dead, so students are looking at the cell wall and air space.)

EXPLORE

Tell students they will be looking at some living cells under the microscope. Explain that each one is a different type of cell. (Don’t tell them what each type is until later.)
Pass out lab activity sheet and read instructions with students. Review safety rules for cutting with sharp objects and use of goggles and laboratory aprons when staining onion slides. Iodine stains clothing! Review microscope procedures, including carrying a microscope with one hand on the arm and one hand under the base.
Distribute materials to each group. Designate a central location for the onion slide preparation to allow careful monitoring of student use of scalpels and iodine stain. Equip it with slides, coverslips, cut onion slices, droppers, iodine and paper towels.
Tell students they have the materials for viewing the onion slide. Designate other areas in the room as a pick up station for the pond water and animal slides. After completing the onion slide observation and drawing, students may view the prepared animal and pond water slide. Monitor students for proper microscope use.
Remind students to draw what they observe in their journal. Students will come back to the drawings and label parts later in the lesson, so no labels are needed on the drawings at this point.
After all students are finished, ask them to describe each slide.
Explain what each of the types of cells are. (Onion – plant cell, Pond water – Protists, and prepared animal slide – animal)
Have students clean and put away all materials.

EXPLAIN

Write the following words on the board: vacuole, cell wall, cytoplasm, cell membrane, chloroplasts, mitochondrion, and nucleus.
Ask students to turn to page 142 in their Prentice Hall Science Explorer textbook.
Ask students which cell they observed was most similar to the diagram. (onion)
Explain to students page 142 shows a diagram of a plant cell and its cell parts. Explain that they are not responsible for all of the cell parts – only vacuole, cell wall, cytoplasm, cell membrane, chloroplasts, mitochondrion and the nucleus.
Ask students if the onion cell looked exactly like the plant cell in the book. Point out that the cell in the book is a diagram which shows the parts illustrated in different colors so students can easily tell them apart. Also, some parts were probably not visible under the microscope. However, they should have seen the nucleus, chloroplasts, cell wall, cytoplasm and cell membrane.
Ask students to look at the animal cell on page 143.
Ask students if any of the cells they looked at were similar to this one? (prepared animal slide)
Tell students to make a color drawing of a plant and an animal cell in their science journal, using the text as a reference. Ask students to draw and label only the parts listed on the board
After students complete their drawings, ask them what parts the plant and animal cells have in common. (vacuole, cytoplasm, cell membrane, mitochondrion and nucleus)
Tell students to look at the information under vacuole for both plant and animal cells. Ask them to use this information and the diagrams. How are vacuoles in plant cells different from those in animal cells? (plants usually have one large vacuole, some animals cells have many small vacuoles; some cells do not have as many vacuoles)
Ask students what is different about the plant and animal cells? (shape – plant cell is square, animal cell is rounded; plant cell has a cell wall for support and chloroplasts for photosynthesis)
Ask students to look at the information under “chloroplasts.”
Ask why an animal cell would not need chloroplasts. (chloroplasts are for producing food, animals do not produce their own food)
Ask students to go back into the text and find the function (job) of each of the parts of the cells. (pages 139 – 145) and write the function of each cell part next to the labels on their diagrams.
Tell student to turn back to the Explore cell drawings in their journals and label any parts they saw under the microscope.
Ask students to create a Venn diagram in their science journal comparing and contrasting plant and animal cells.

ELABORATE

1.Show students a picture of an apple, and then show them an apple. Use the apple as an example of a 3 dimensional object, and the picture of the apple as a 2 dimensional representation of the apple.

2.Ask students if the cells they observed were 2 or 3 dimensional.

3.Explain to students that cells are 3 dimensional. They are not flat. They just appear flat when viewed under a microscope because they are so small.

4.Explain to students they will make a model of what a cell might really look like if it were larger.

5.Provide students with materials such as small ziplock bags, Karo syrup, small boxes, marbles,beads, yarn, pipe cleaners and other readily available materials for organelles.

6.Assign half of the lab groups to create a plant cell and half to create an animal cell.

7.Guide the students with cell membrane (baggie), cell wall (box) and cytoplasm (syrup.) The rest of the parts should be up to the students.

8.After students are finished with their cell models, ask them to label each part and construct a key to show what each material represents. Ask students to explain how the cell models are different from the cells they observed under the microscope. Explain to students that these are MODELS of cells but that models can often be used to help us study things that are too small to see. Display the cell models.

EVALUATE

Ask students to describe the function or job of the nucleus. (The nucleus acts as the “brain” of the cell and provides instructions for the cell to follow.)
Ask students if they can think of examples of other people or objects that provide important instructions to follow. (President, parents, principal, computer are possible answers)
Go over the function (job) of each of the parts with students. (Cell wall provides shape, and protects and supports the cell; Cell membrane controls what goes into and comes out of the cell; Mitochondrion produce the energy for the cell; Chloroplasts are used to produce food; Vacuoles store food, water and waste products; Cytoplasm contains all the parts of the cell – keeps everything in its place)
Ask students to think of something or someone who might have a job that is similar to the cell parts.
Have students work in partners to create a collage to show the functions (jobs) of each of the cell parts. (ex: cell wall gives shape, protects and supports the cell – bricks around a building; cell membrane controls what goes into and comes out of the cell – border between countries; mitochondrion produce the energy for the cell – a power plant, electricity, food; chloroplasts are used to produce food – stove, chef, McDonald’s; vacuoles store food and water <also waste products> - refrigerator, septic system; cytoplasm contains all the parts of the cell and keeps everything in place –building, classroom ) Make sure each picture is labeled with the cell part.
As an extension, you may have students write why they used a particular picture to represent each cell part function (job).
Have students share their collages, explaining why they chose the pictures to represent each cell part. Use the rubric to evaluate the student’s data sheet for the cell structure investigation.

Building A Model : Cell

Use the following rubric to evaluate the student’s cell model.

Lab Report : Cell StructureStudent Name: ______

CATEGORY / 4 / 3 / 2 / 1
Participation / Used time well in lab and focused attention on the experiment. / Used time pretty well. Stayed focused on the experiment most of the time. / Did the lab but did not appear very interested. Focus was lost on several occasions. / Participation was minimal OR student was hostile about participating.
Drawings/Diagrams / Clear, accurate diagrams are included and make the experiment easier to understand. / Diagrams are included - neat. / Diagrams are included. / Needed diagrams are missing.
Summary / Summary accurately describes the skills learned, the information learned. / Summary accurately describes the information learned / Summary describes the information learned. / No summary is written.

Use the following rubric to evaluate the student’s cell model.

Making A Model of a Cell

Student Name: ______
CATEGORY / 4 / 3 / 2 / 1
Construction -Materials / Appropriate materials were selected and creatively modified in ways that made them even better. / Appropriate materials were selected and there was an attempt at creative modification to make them even better. / Appropriate materials were selected. / Inappropriate materials were selected to construct the cell.
Construction - Care Taken / Great care taken in construction process so that the cell is neat, attractive and follows plans accurately. / Construction was careful and accurate for the most part, but 1-2 details could have been refined for a more attractive cell. / Construction accurately followed the plans, but 3-4 details could have been refined for a more attractive cell. / Construction appears careless or haphazard. Many details need refinement for a strong or attractive cell.

Use the following rubric to evaluate the student’s cell analogy.

Making A Collage : Cell Analogy
Student Name: ______
CATEGORY / 4 / 3 / 2 / 1
Time and Effort / Class time was used wisely. Much time and effort went into the planning and design of the collage. / Class time was used wisely. Student could have put in a little more time and effort / Class time was not always used wisely. / Class time was not used wisely.
Creativity / Several of the graphics or objects used in the collage reflect an exceptional degree of student creativity. / One or two of the graphics or objects used in the collage reflect student creativity. / Ideas were typical rather than creative. / The student did not make any effort.
Materials Details/Advanced Preparation:

ENGAGE

White board or chalkboard (T)

White board markers or chalk (T)

Microscopes (L)

Microscope slides - 1 (L)

Cork – if you do not want to give the students a scalpel or razor you need to cut these; cut a very thin slice (L)

Razor or scalpel – number depends on whether teacher or students cut cork (T)

Science journal (I)

Pen or pencil (I)

EXPLORE

Student activity sheet (I)

Microscope (L)

Razor or scalpel – refer to above directions (T or L)

Onion (T)

Iodine (L)

Dropper (L)

3 microscope slides (L)

3 coverslips (L)

apron (I) – or if short supply can be used by student staining slide

goggles (I)

paper towels (L)

tweezers (L)

liver or animal cell slides (commercially prepared) (L)

Container with pond water – try to get pond water several days in advance (T)

Dropper – place in pond water (T)

EXPLAIN

Whiteboard or chalkboard (T)

Markers or chalk (T)

Textbook (I)

Science journal (I)

Pencil (I)

Map pencils or colors (I)

ELABORATE

Picture of an apple (T)

Apple (T)

Small boxes (check boxes or any other small box) (L)

Small ziplock bags (L)

Karo syrup (L)

Beads (L)

Marbles (L)

Yarn (L)

Any other materials you deem appropriate (L)

Textbook (I)

EVALUATE

Textbook (I)

Old magazines (I)

Markers (I)

Glue (I)

Large construction paper (I)

Rubrics - attached

Teacher Background Information:

All living things are made of cells. Some organisms or living things consist of one cell. Other organisms, such as humans, are made of many different types of cells. Protists, bacteria and some fungi are one-celled organisms. A pond water sample will most likely contain many examples of protists.

One of the first people to observe a “cell” under the microscope was Robert Hooke. He saw the same things that students will observe when looking at cork under the microscope. Hooke observed thinly sliced piece of cork with his compound microscope, and called the tiny, rectangular areas “cells” because they looked like little rooms.

Cells are made up of tiny parts called organelles. Both animal and plant have a nucleus, cell membrane, cytoplasm, and mitochondria. The nucleus is the control center of the cell and contains the cell’s genetic material. The cell membrane separates the cell from the outside world. It allows water and food to enter the cell and waste products to leave the cell. The area between the cell membrane and the cell contains a material called cytoplasm. Both animal and plant cells also contain vacuoles. However, a plant cell vacuole is extremely large. Most of the water in a plant cell is stored in the vacuole. Plants wilt when the central vacuoles of their cells shrink because of lack of water. Animal cells contain many smaller vacuoles to store food, water and waste products. The mitochondria are rod shaped organelles known as the “powerhouses” of the cell – meaning they produce most of the energy the plant needs to carry out its functions. Cells that need a lot of energy (muscle cells) have many mitochondria. Vacuoles, chloroplasts and mitochondria are all located in the cytoplasm.

Plant and animal cells have many parts in common, but they are also different in several ways. Plant cells have a cell wall. The cell wall gives the plant cell its shape. It also protects and supports the plant cell. Plants also contain large green chloroplasts. Chloroplasts capture light energy from the sun to produce food by photosynthesis. Animal cells do not contain chloroplasts.

Targeted TEKS:

6.1 The student conducts field and laboratory investigations using safe, environmentally appropriate, and ethical practices. The student is expected to:

(A) demonstrate safe practices during field and laboratory investigations

(B) make wise choices in the use and conservation of resources and the disposal or recycling of materials.

6.2 The student uses scientific inquiry methods during field and laboratory investigations. The student is expected to

(B) collect data by observing and measuring