Eukaryotic Cell Organization: Breaking the Jell-O Salad

Mold Stephanie Aamodt, LSU-Shreveport Beverly Clendening, Hofstra Univ.

Hans Landel, Edmonds Community College Doug Luckie, MSU

John Rebers, Northern Michigan University

Description of the Challenge   Our group: Cell/Developmental Biology   Target: introductory biology course, majors or non-

majors, of any size   The Misunderstanding: the eukaryotic cell is a collection

of individual and isolated parts, randomly arranged in the cell   The “Jell-O Salad” paradigm

  You will see later what we want students to think instead the “Jell-O Salad” model (what our objectives are) because we do not want to prejudice you, but we can tell you:   Emphasis on model-based reasoning, relying on analogy   Specific objectives are in our course description document

Learning Goals/Objectives After completing this unit the student will:

•  Be able to describe cellular organization and the way this organization relates to function

•  Be able to relate the organization of the cell to different functional activities

•  Be able to make reasonable assumptions about the reasons for differences between prokaryotic and eukaryotic cells

 At the end of the course, the student will: •  Be able to apply the idea that function is dependent on

organized structure to the organization of living things, including the following levels:   o Chemical/molecular   o Cellular/organelle   o Tissue/organ/system   o Organisms/ecosystems

Preliminaries  Before this class

 Preliminary introduction to macromolecules  Class discussion: Define “living things” and generate

list of requirements   Introduce cells as the “smallest unit of life”  All cells have membrane, DNA, cytoplasm

“The class part”  Run through first part of class

Summary  Car is organized

 parts   subsystems   systems  connections

 Organization is important to function  Car has processes

  simultaneous  connections

 Processes important to function  Processes and Organization are interdependent

“The FIRST part”  Describe rest of class

TRANSITION: Bring the Class to Biology

  have been examining a non-living object   let’s use what we have learned about the car to

examine a living object -- the human body

TRANSITION: Bring the Class to Biology   The procedures with the car has served as a model for what

we would like the students to do.   Car will serve as an analogy   Now use the same procedure as with the car, but with the

human body   list functions body must perform to live   list body parts   categorize body parts according to function   parts must be assembled in correct locations   certain activities must occur for body to function   may or may not include formative assessment by performing

“perturb and predict” exercises

Concept Maps  NOTE: Homework (assessment) will include

concept mapping of cell parts with respect to function

  If students have not been introduced to concept maps, a good place to introduce them is at the point when they are asked to categorize the parts of the body according to function. This will model for them what we would like them to do in the homework assignment.

Possible example concept map: plants

Example of a poor concept map   “Sentence-in-a-box”   Poor concept map   Good concept map

should show complex relationships   One part can have

multiple relationships   Use linking terms to

show how parts are related

  Focus on most important connections

FOCUS: Bring the class to the cell level

  Important transition  Have established a context for

describing and understanding the cell

Break the “Jell-O salad mold”  More than a boring parts list  Structures are not isolated; they are

interconnected  Structures are not randomly placed; they are

highly organized  The organization is not static; it is dynamic

Repeat steps 1 through 3  Ask the class to list functions cell must

perform to live, and the parts of the cell  Can the students group the parts according

to function?  Can the students organize the parts of the

cell? Make connections?

Recognize that student knowledge is limited

 Students will have some prior knowledge, but it will be simple, pat definitions.

 Allow class to explicitly identify what they don’t know or understand.

 Emphasize that what we don’t know as a class will direct the rest of the unit.

Model a dynamic view of the cell  Present an exciting mini-lecture on one cell

structure or organelle as an example for the class.   Include a video clip of a cell process such as

mitosis or transport or a cell in motion.  Describe how the structure is made of smaller

parts that fit together precisely to allow a specific, controlled process

  (Here, “model” means showing students what we expect them to do)

Encourage students to think

 The contextual framework will be reinforced by homework and assessments.

 The dynamic, highly organized view of life will be further developed in classes on cellular respiration, mitosis and most other topics, as well, as the course continues into the study of cell biology.

Assignment

1.  Complete the structure/function chart for the cell that was begun in class. The information can be found in Chapter x of your textbook.

•  this forces the students to learn the parts on their own, but within the context of function

2. Draw a concept map that shows the spatial and functional relationships among  nucleus  endoplasmic reticulum   ribosomes   mitochondria  cytosol   synthesis of macromolecules (anabolic metabolism)  breakdown of macromolecules for energy production

(catabolic metabolism) Examples of connecting phrases (is connected to, takes

place in , etc.)   this assesses their understanding of the concepts of

spatial and temporal organization

3. Label the cell compartments with their functions.

4. Predict, in detail, what would happen if   Group A

•  there was a hole in the cell membrane. •  the cell had no mitochondria. •  a mature cell lost its nucleus.

 Group B •  none of the ribosomes were attached to the endoplasmic

reticulum. •  the process of vesicle formation could not occur (the Golgi

apparatus could not form vesicles).  Pick one from Group A and one from Group B

  this assesses their understanding of the importance of spatial and temporal organization of cells

The EXCITING significance of this unit   It covers a BIG idea in Biology   It is “scalable” for use in other topics

The Big Idea   Living Things Are Organized.

  Spatially- certain parts are located in certain places

  Temporally - certain processes take place in a certain order

  Function is dependent on both spatial and temporal organization

  Interconnected   Interactions   Hierarchical (systems, subsystems, sub-

subsystems . . .)

Permeation of the “Big Idea”   you can (and we think you should) re-examine the

importance of spatial and temporal organization when the following cellular topics are discussed  Metabolism  Mitosis  Protein synthesis   Intracellular signaling   Intercellular signaling

  our assessments can be used after any of these topics, and in midterm and final exams

“Active Transport” of the “Big Idea”

 The Big Idea applies (by definition) to all levels of biology. We think it should be continually stressed.

•  Macromolecules •  Organelles •  Tissues •  Organs •  Organisms •  Communities •  Ecosystems

Scalability of Exercise  Because life is hierarchically organized,

with each level exhibiting spatial and temporal organization (i.e., because it is a Big Idea), this exercise can be used at any level.

 (it has wide applicability)

Living things are organized.

  Replace “Living Things” with . . . •  Macromolecules •  Organelles •  Tissues •  Organs •  Organisms •  Communities •  Ecosystems

Revisions?  Feedback from FIRST participants suggests

  Transition (human body) step can be left out   Car analogy has sexual bias -- women will

have a harder time relating to it •  we had discussed this and had decided to address

this by calling on women first •  also, you can use ANY object you would like as

your analogy, as long as it it sufficiently complex, has processes, and is understandable by the majority of your students (see course description document)