1. Chapter 4 A Tour of the Cell
BIO 101
Chapter 4 A Tour of the Cell

2. Robert Hooke the originator of the word 'cell' 1665

3. As microscopes improved so did our understanding of the cell.

4. 4.1 Microscopes reveal the world of the cell
A variety of microscopes have been developed for a clearer view of cells and cellular structure. They differ in
______________
Light microscope (LM)
Student Misconceptions and Concerns
1. Students typically cannot distinguish between the concepts of resolution and magnification. However, pixels and resolution of digital images can help clarify the distinction. Consider printing the same image at high and low resolution and enlarging the same image at two different levels of resolution. Teaching Tip 2 below suggests another related exercise.
2. Students can easily feel overwhelmed by the large numbers of structures and related functions in this chapter. For such students, Module 4.22 might be the best place to start when approaching this chapter. Students might best comprehend the content in Chapter 4 by reviewing the categories of organelles and related functions in Table 4.22 and referring to it regularly as the chapter is studied and/or discussed.
Teaching Tips
1. Challenge students to identify other examples of technology that have extended our senses. Chemical probes can identify what we cannot taste, listening devices detect what we do not normally hear, night vision and ultraviolet (UV) cameras see or magnify wavelengths beyond our vision, etc. Students can be assigned the task of preparing a short report on one of these technologies.
2. Here is a chance to demonstrate resolving power in the classroom. Use a marker and your classroom marker board to make several pairs of dots separated by shorter and shorter distances. Start out with two dots clearly separated apart—perhaps by 4–5 cm—and end with a pair of dots that touch. Label them a, b, c, etc. Ask your students to indicate the letters of the pairs of points that they can distinguish as separate; this is the definition of resolution for their eyes (they need not state their answers publicly, to avoid embarrassment).
3. Most biology laboratories have two types of microscopes for student use: a dissection (or stereo-) microscope, and a compound light microscope using microscope slides. The way these scopes function parallels the workings of electron microscopes. Dissection microscopes are like an SEM—both rely upon a beam reflected off a surface. As you explain this to your class, hold up an object, identify a light source in the room, and explain that our eyes see most images when our eyes detect light that has reflected off the surface of an object. Compound light microscopes are like TEMs, in which a beam is transmitted through a thin sheet of material. If you have an overhead or other strong light source, hold up a piece of paper between your eye and the light source. You will see the internal detail of the paper as light is transmitted through the paper to your eye the same way a compound light microscope or TEM works!
© 2012 Pearson Education, Inc. 4

5. 4.1 Microscopes reveal the world of the cell
Electron microscope (EM)
2 types
Student Misconceptions and Concerns
1. Students typically cannot distinguish between the concepts of resolution and magnification. However, pixels and resolution of digital images can help clarify the distinction. Consider printing the same image at high and low resolution and enlarging the same image at two different levels of resolution. Teaching Tip 2 below suggests another related exercise.
2. Students can easily feel overwhelmed by the large numbers of structures and related functions in this chapter. For such students, Module 4.22 might be the best place to start when approaching this chapter. Students might best comprehend the content in Chapter 4 by reviewing the categories of organelles and related functions in Table 4.22 and referring to it regularly as the chapter is studied and/or discussed.
Teaching Tips
1. Challenge students to identify other examples of technology that have extended our senses. Chemical probes can identify what we cannot taste, listening devices detect what we do not normally hear, night vision and ultraviolet (UV) cameras see or magnify wavelengths beyond our vision, etc. Students can be assigned the task of preparing a short report on one of these technologies.
2. Here is a chance to demonstrate resolving power in the classroom. Use a marker and your classroom marker board to make several pairs of dots separated by shorter and shorter distances. Start out with two dots clearly separated apart—perhaps by 4–5 cm—and end with a pair of dots that touch. Label them a, b, c, etc. Ask your students to indicate the letters of the pairs of points that they can distinguish as separate; this is the definition of resolution for their eyes (they need not state their answers publicly, to avoid embarrassment).
3. Most biology laboratories have two types of microscopes for student use: a dissection (or stereo-) microscope, and a compound light microscope using microscope slides. The way these scopes function parallels the workings of electron microscopes. Dissection microscopes are like an SEM—both rely upon a beam reflected off a surface. As you explain this to your class, hold up an object, identify a light source in the room, and explain that our eyes see most images when our eyes detect light that has reflected off the surface of an object. Compound light microscopes are like TEMs, in which a beam is transmitted through a thin sheet of material. If you have an overhead or other strong light source, hold up a piece of paper between your eye and the light source. You will see the internal detail of the paper as light is transmitted through the paper to your eye the same way a compound light microscope or TEM works!
© 2012 Pearson Education, Inc. 5

6. 4.1 Microscopes reveal the world of the cell
Using light microscopes, scientists studied
microorganisms,
animal and plant cells, and
some structures within cells.
In the 1800s, these studies led to cell theory
_____________________
______________________
Student Misconceptions and Concerns
1. Students typically cannot distinguish between the concepts of resolution and magnification. However, pixels and resolution of digital images can help clarify the distinction. Consider printing the same image at high and low resolution and enlarging the same image at two different levels of resolution. Teaching Tip 2 below suggests another related exercise.
2. Students can easily feel overwhelmed by the large numbers of structures and related functions in this chapter. For such students, Module 4.22 might be the best place to start when approaching this chapter. Students might best comprehend the content in Chapter 4 by reviewing the categories of organelles and related functions in Table 4.22 and referring to it regularly as the chapter is studied and/or discussed.
Teaching Tips
1. Challenge students to identify other examples of technology that have extended our senses. Chemical probes can identify what we cannot taste, listening devices detect what we do not normally hear, night vision and ultraviolet (UV) cameras see or magnify wavelengths beyond our vision, etc. Students can be assigned the task of preparing a short report on one of these technologies.
2. Here is a chance to demonstrate resolving power in the classroom. Use a marker and your classroom marker board to make several pairs of dots separated by shorter and shorter distances. Start out with two dots clearly separated apart—perhaps by 4–5 cm—and end with a pair of dots that touch. Label them a, b, c, etc. Ask your students to indicate the letters of the pairs of points that they can distinguish as separate; this is the definition of resolution for their eyes (they need not state their answers publicly, to avoid embarrassment).
3. Most biology laboratories have two types of microscopes for student use: a dissection (or stereo-) microscope, and a compound light microscope using microscope slides. The way these scopes function parallels the workings of electron microscopes. Dissection microscopes are like an SEM—both rely upon a beam reflected off a surface. As you explain this to your class, hold up an object, identify a light source in the room, and explain that our eyes see most images when our eyes detect light that has reflected off the surface of an object. Compound light microscopes are like TEMs, in which a beam is transmitted through a thin sheet of material. If you have an overhead or other strong light source, hold up a piece of paper between your eye and the light source. You will see the internal detail of the paper as light is transmitted through the paper to your eye the same way a compound light microscope or TEM works!
© 2012 Pearson Education, Inc. 6

7. Same magnification, different type microscope

8. 4.2 The small size of cells relates to the need to exchange materials across the plasma membrane
Cell size must
be large enough to house DNA, proteins, and structures needed to survive and reproduce, but
remain small enough to allow for a surface-to-volume ratio that will allow adequate exchange with the environment.
Student Misconceptions and Concerns
1. Students often think of the function of cell membranes as mainly containment, like that of a plastic bag. Consider relating the functions of membranes to our human skin. (For example, both membranes and our skin detect stimuli, engage in gas exchange, and serve as sites of excretion and absorption.)
2. Students can easily feel overwhelmed by the large numbers of structures and related functions in this chapter. For such students, Module 4.22 might be the best place to start when approaching this chapter. Students might best comprehend the content in Chapter 4 by reviewing the categories of organelles and related functions in Table 4.22 and referring to it regularly as the chapter is studied and/or discussed.
Teaching Tips
1. Even in college, students still struggle with the metric system. When discussing the scale of life, consider bringing a meter stick to class. The ratio of a meter to a millimeter is the same as the ratio of a millimeter to a micron: 1,000 to 1.
2. Here is another way to explain surface-to-volume ratios. Have your class consider this situation. You purchase a set of eight coffee mugs, each in its own cubic box, for a wedding present. You can wrap the eight boxes together as one large cube, or wrap each of the eight boxes separately. Either way, you will be wrapping the same volume. However, wrapping the mugs separately requires much more paper. This is because the surface-to-volume ratio is greater for smaller objects.
3. The hydrophobic and hydrophilic ends of a phospholipid molecule create a lipid bilayer. The hydrophobic edges of the layer will naturally seal to other such edges, eventually wrapping a sheet into a sphere that can enclose water (a simple cell). Furthermore, because of these hydrophobic properties, lipid bilayers are also self-healing. That the properties of phospholipids emerge from their organization is worth emphasizing to students.
4. You might wish to share a very simple analogy that works very well for some students. A cell membrane is a little like a peanut butter and jelly sandwich with jellybeans poked into it. The bread represents the hydrophilic portions of the bilayer (and bread does indeed quickly absorb water). The peanut butter and jelly represent the hydrophobic regions (and peanut butter, containing plenty of oil, is generally hydrophobic). The jellybeans stuck into the sandwich represent proteins variously embedded partially into or completely through the membrane. Transport proteins would be like the jellybeans that poke completely through the sandwich. Analogies are rarely perfect. Challenge your students to critique this analogy by finding exceptions. (For example, this analogy does not include a model of the carbohydrates on the cell surface.) 8

9. CELL OR PLASMA MEMBRANES
hydrophilic head (phosphate)
hydrophobic
tail (lipid)
phospholipid
bilayers
lipid bilayer
surround cell &
many organelles
cytoplasm
extracellular
fluid

10. Organization of Cell Membrane

11. Hydrophobic region of a protein
Outside cell
Hydrophilic heads
Hydrophobic region of a protein
Hydrophobic tails
Hydrophilic region of a protein
Phospholipid
Figure 4.2B A plasma membrane: a phospholipid bilayer with associated proteins
Inside cell
Channel protein
Proteins 11

12. Types of Cells http://www.cellsalive.com/howbig.htm
Cells are divided into 2 major types:
Prokaryotes and Eukaryotes
Animal Plant

13. Draw and Label Generalized Plant Cell Generalized Animal Cell
Prokaryotic Cell

14. 4.3 Prokaryotic cells are structurally simpler than eukaryotic cells
Bacteria and archaea are prokaryotic cells.
All other forms of life are composed of eukaryotic cells.
Prokaryotic and eukaryotic (ALL) cells have
___________________________
Eukaryotic cells have a membrane-bound nucleus and
other organelles.
Prokaryotes have a nucleoid and no true organelles.
Student Misconceptions and Concerns
Students can easily feel overwhelmed by the large numbers of structures and related functions in this chapter. For such students, Module 4.22 might be the best place to start when approaching this chapter. Students might best comprehend the content in Chapter 4 by reviewing the categories of organelles and related functions in Table 4.22 and referring to it regularly as the chapter is studied and/or discussed.
Teaching Tips
1. A visual comparison of prokaryotic and eukaryotic cells, such as that found in Figure 1.3, can be very helpful when discussing the key differences between these cell types. These cells are strikingly different in size and composition. Providing students with a visual reference point rather than simply listing these traits will help them better retain this information.
2. Students might wrongly conclude that prokaryotes are typically one-tenth the volume of eukaryotic cells. A difference in diameter of a factor of ten translates into a much greater difference in volume. If students recall enough geometry, you may want to challenge them to calculate the difference in the volume of two cells with diameters that differ by a factor of ten (the answer is about 1,000).
3. Germs—here is a term that we learn early in our lives but that is rarely well defined. Students may appreciate a biological explanation. The general use of germs is a reference to anything that causes disease. This may be a good time to sort the major disease-causing agents into three categories: (1) bacteria (prokaryotes), (2) viruses (not yet addressed), and (3) single-celled and multicellular eukaryotes (athlete’s foot is a fungal infection; malaria is caused by a unicellular eukaryote).
4. Module 4.3 mentions how antibiotics can specifically target prokaryotic but not eukaryotic cells, providing a good segue into discussion of the evolution of antibiotic resistance. Teaching tips and ideas for related lessons can be found at
© 2012 Pearson Education, Inc. 14

15. 4.3 Prokaryotic cells are structurally simpler than eukaryotic cells
The DNA of prokaryotic cells is coiled into a region called the nucleoid, but no membrane surrounds the DNA.
Student Misconceptions and Concerns
Students can easily feel overwhelmed by the large numbers of structures and related functions in this chapter. For such students, Module 4.22 might be the best place to start when approaching this chapter. Students might best comprehend the content in Chapter 4 by reviewing the categories of organelles and related functions in Table 4.22 and referring to it regularly as the chapter is studied and/or discussed.
Teaching Tips
1. A visual comparison of prokaryotic and eukaryotic cells, such as that found in Figure 1.3, can be very helpful when discussing the key differences between these cell types. These cells are strikingly different in size and composition. Providing students with a visual reference point rather than simply listing these traits will help them better retain this information.
2. Students might wrongly conclude that prokaryotes are typically one-tenth the volume of eukaryotic cells. A difference in diameter of a factor of ten translates into a much greater difference in volume. If students recall enough geometry, you may want to challenge them to calculate the difference in the volume of two cells with diameters that differ by a factor of ten (the answer is about 1,000).
3. Germs—here is a term that we learn early in our lives but that is rarely well defined. Students may appreciate a biological explanation. The general use of germs is a reference to anything that causes disease. This may be a good time to sort the major disease-causing agents into three categories: (1) bacteria (prokaryotes), (2) viruses (not yet addressed), and (3) single-celled and multicellular eukaryotes (athlete’s foot is a fungal infection; malaria is caused by a unicellular eukaryote).
4. Module 4.3 mentions how antibiotics can specifically target prokaryotic but not eukaryotic cells, providing a good segue into discussion of the evolution of antibiotic resistance. Teaching tips and ideas for related lessons can be found at
© 2012 Pearson Education, Inc. 15

16. 4.4 Eukaryotic cells are partitioned into functional compartments
The structures and organelles of eukaryotic cells perform four basic functions.
The nucleus and ribosomes are involved in the ________________ of the cell.
The endoplasmic reticulum, Golgi apparatus, lysosomes, vacuoles, and peroxisomes are involved in the _________________, _______________, __________________ .
Mitochondria in all cells and chloroplasts in plant cells are involved in _____________ processing.
Structural _______________ , , and _______________________between cells are functions of the cytoskeleton, plasma membrane, and cell wall.
Student Misconceptions and Concerns
Students can easily feel overwhelmed by the large numbers of structures and related functions in this chapter. For such students, Module 4.22 might be the best place to start when approaching this chapter. Students might best comprehend the content in Chapter 4 by reviewing the categories of organelles and related functions in Table 4.22 and referring to it regularly as the chapter is studied and/or discussed.
Teaching Tips
Some instructors have found that challenging students to come up with analogies for the many eukaryotic organelles is a highly effective teaching method. Students may wish to construct one inclusive analogy between a society or factory and a cell or construct separate analogies for each organelle. As with any analogy, it is important to list the similarities and exceptions.
© 2012 Pearson Education, Inc. 16

17. 4.4 Eukaryotic cells are partitioned into functional compartments
Almost all of the organelles and other structures of animals cells are present in plant cells.
A few exceptions exist:
PLANT CELLS
ANIMAL CELLS
Student Misconceptions and Concerns
Students can easily feel overwhelmed by the large numbers of structures and related functions in this chapter. For such students, Module 4.22 might be the best place to start when approaching this chapter. Students might best comprehend the content in Chapter 4 by reviewing the categories of organelles and related functions in Table 4.22 and referring to it regularly as the chapter is studied and/or discussed.
Teaching Tips
Some instructors have found that challenging students to come up with analogies for the many eukaryotic organelles is a highly effective teaching method. Students may wish to construct one inclusive analogy between a society or factory and a cell or construct separate analogies for each organelle. As with any analogy, it is important to list the similarities and exceptions.
© 2012 Pearson Education, Inc. 17

18. Smooth endoplasmic reticulum Rough endoplasmic reticulum NUCLEUS:
Figure 4.4A
Smooth endoplasmic reticulum
Rough endoplasmic reticulum
NUCLEUS:
Nuclear envelope
Chromatin
Nucleolus
NOT IN MOST PLANT CELLS:
Centriole
Lysosome
Peroxisome
Figure 4.4A An animal cell
Ribosomes
Golgi apparatus
CYTOSKELETON:
Microtubule
Mitochondrion
Intermediate filament
Microfilament
Plasma membrane 18

19. Rough endoplasmic reticulum NUCLEUS: Nuclear envelope Chromatin
Figure 4.4B
Rough endoplasmic reticulum
NUCLEUS:
Nuclear envelope
Chromatin
Ribosomes
Nucleolus
Smooth endoplasmic reticulum
Golgi apparatus
NOT IN ANIMAL CELLS:
CYTOSKELETON:
Microtubule
Central vacuole
Intermediate filament
Chloroplast
Cell wall
Microfilament
Plasmodesma
Figure 4.4B A plant cell
Mitochondrion
Peroxisome
Plasma membrane
Cell wall of adjacent cell 19

20. 4.5 The nucleus is the cell’s genetic control center
contains most of the cell’s DNA and
controls the cell’s activities by directing protein synthesis by making messenger RNA (mRNA).
DNA and associated proteins form structures called chromosomes.
Student Misconceptions and Concerns
1. Students often enter college with misunderstandings about the interrelationship between DNA, a chromosome, and a replicated chromosome often photographed just prior to mitosis or meiosis. Consider specifically distinguishing between these important cellular components early in your discussions of the nucleus.
2. Conceptually, some students seem to benefit from the well-developed cell-factory analogy developed in the text. The use of this analogy in lecture might help to anchor these relationships. As mentioned before, challenge students to find exceptions in the analogy, an exercise that promotes critical thinking.
Teaching Tips
1. Not all human cells have 46 chromosomes per human cell. Some of your more knowledgeable students may like to guess the exceptions. These include gametes, some of the cells that produce gametes, and adult red blood cells in mammals.
2. If you wish to continue the text’s factory analogy, nuclear pores might be said to function most like the door to the boss’s office. Through these doors, directions to the rest of the factory, including ribosomal components, are transmitted.
3. Noting the main flow of genetic information on the board as DNA to RNA to protein will provide a useful reference for students when explaining these processes. As a review, have students note where new molecules of DNA, rRNA, mRNA, ribosomes, and proteins are produced in a cell.
4. If you want to challenge your students further, ask them to consider the adaptive advantage of using mRNA to direct the production of proteins instead of using DNA directly. One advantage is that DNA is better protected in the nucleus and that mRNA, exposed to more damaging cross-reactions in the cytosol, is the temporary working copy of the genetic material. In some ways, this is like making a working photocopy of an important document, keeping the original copy safely stored away (perhaps like the U.S. Constitution).
5. Consider challenging your students to explain how we can have four main types of organic molecules functioning in specific roles in our cells, yet DNA and RNA only specifically dictate the generation of proteins (and more copies of DNA and RNA). How is the production of specific types of carbohydrates and lipids in cells controlled? (Answer: primarily by the specific properties of enzymes.) 20

21. THE NUCLEUS nuclear envelope double membranes w/ pores chromosomes
nucleolus
chromosomes
threadlike; look
grainy, ;unwound DNA (chromatin)
membrane facing cytoplasm
pore
membrane facing
inside of nucleus

22. 4.5 The nucleus is the cell’s genetic control center
The nuclear envelope
is a double membrane and
has pores that allow material to flow in and out of the nucleus.
The nuclear envelope is attached to a network of cellular membranes called the endoplasmic reticulum.
Student Misconceptions and Concerns
1. Students often enter college with misunderstandings about the interrelationship between DNA, a chromosome, and a replicated chromosome often photographed just prior to mitosis or meiosis. Consider specifically distinguishing between these important cellular components early in your discussions of the nucleus.
2. Conceptually, some students seem to benefit from the well-developed cell-factory analogy developed in the text. The use of this analogy in lecture might help to anchor these relationships. As mentioned before, challenge students to find exceptions in the analogy, an exercise that promotes critical thinking.
Teaching Tips
1. Not all human cells have 46 chromosomes per human cell. Some of your more knowledgeable students may like to guess the exceptions. These include gametes, some of the cells that produce gametes, and adult red blood cells in mammals.
2. If you wish to continue the text’s factory analogy, nuclear pores might be said to function most like the door to the boss’s office. Through these doors, directions to the rest of the factory, including ribosomal components, are transmitted.
3. Noting the main flow of genetic information on the board as DNA to RNA to protein will provide a useful reference for students when explaining these processes. As a review, have students note where new molecules of DNA, rRNA, mRNA, ribosomes, and proteins are produced in a cell.
4. If you want to challenge your students further, ask them to consider the adaptive advantage of using mRNA to direct the production of proteins instead of using DNA directly. One advantage is that DNA is better protected in the nucleus and that mRNA, exposed to more damaging cross-reactions in the cytosol, is the temporary working copy of the genetic material. In some ways, this is like making a working photocopy of an important document, keeping the original copy safely stored away (perhaps like the U.S. Constitution).
5. Consider challenging your students to explain how we can have four main types of organic molecules functioning in specific roles in our cells, yet DNA and RNA only specifically dictate the generation of proteins (and more copies of DNA and RNA). How is the production of specific types of carbohydrates and lipids in cells controlled? (Answer: primarily by the specific properties of enzymes.) 22

23. NUCLEOLUS (Nucleoli) Found within the nucleus
Produces ribosomes (rRNA)

24. 4.6 Ribosomes make proteins for use in the cell and export
Ribosomes are involved in the cell’s protein synthesis.
Ribosomes are synthesized from rRNA produced in the nucleolus.
Cells that must synthesize large amounts of protein have a large number of ribosomes.
Some ribosomes are free ribosomes; others are bound.
Student Misconceptions and Concerns
Conceptually, some students seem to benefit from the well-developed cell-factory analogy developed in the text. The use of this analogy in lecture might help to anchor these relationships. As mentioned before, challenge students to find exceptions in the analogy, an exercise that promotes critical thinking.
Teaching Tips
1. If you wish to continue the text’s factory analogy, nuclear pores might be said to function most like the door to the boss’s office. Through these doors, directions to the rest of the factory, including ribosomal components, are transmitted.
2. Noting the main flow of genetic information on the board as DNA to RNA to protein will provide a useful reference for students when explaining these processes. As a review, have students note where new molecules of DNA, rRNA, mRNA, ribosomes, and proteins are produced in a cell.
3. If you want to challenge your students further, ask them to consider the adaptive advantage of using mRNA to direct the production of proteins instead of using DNA directly. One advantage is that DNA is better protected in the nucleus and that mRNA, exposed to more damaging cross-reactions in the cytosol, is the temporary working copy of the genetic material. In some ways, this is like making a working photocopy of an important document, keeping the original copy safely stored away (perhaps like the U.S. Constitution).
4. Consider challenging your students to explain how we can have four main types of organic molecules functioning in specific roles in our cells, yet DNA and RNA only specifically dictate the generation of proteins (and more copies of DNA and RNA). How is the production of specific types of carbohydrates and lipids in cells controlled? (Answer: primarily by the specific properties of enzymes.)
© 2012 Pearson Education, Inc. 24

25. Colorized TEM showing ER and ribosomes
Figure 4.6
Ribosomes ER
Cytoplasm
Endoplasmic reticulum (ER)
Free ribosomes
Bound ribosomes
Figure 4.6 The locations and structure of ribosomes
Colorized TEM showing ER and ribosomes
mRNA
Diagram of a ribosome
Protein 25

26. 4.7 Many cell organelles are connected through the endomembrane system
Many of the membranes within a eukaryotic cell are part of the endomembrane system.
Some of these membranes are physically connected and some are related by the transfer of membrane segments by tiny vesicles (sacs made of membrane).
Many of these organelles work together in the
synthesis,
storage, and
export of molecules.
Student Misconceptions and Concerns
1. Students can have trouble relating many cell organelles to their diverse functions. They may not realize that Modules 4.7–4.12 introduce the primary organelles in the general order that they function in the production and release of secretory proteins. Products and information generally move from the central nucleus to the rough ER, through the more peripherally located Golgi apparatus and the secretory vesicles, and finally to the outer plasma membrane. Emphasizing the flow from center to periphery in this process can help students to remember the function of individual organelles as they recall the steps of the sequence.
2. Conceptually, some students seem to benefit from the well-developed cell-factory analogy developed in the text. The use of this analogy in lecture might help to anchor these relationships. As mentioned before, challenge students to find exceptions in the analogy, an exercise that promotes critical thinking.
Teaching Tips
Point out to your students that the endoplasmic reticulum is continuous with the outer nuclear membrane. This explains why the ER is usually found close to the nucleus.
© 2012 Pearson Education, Inc. 26

27. 4.7 The endomembrane system
The endomembrane system includes
the nuclear envelope,
endoplasmic reticulum (ER),
Golgi apparatus,
lysosomes,
vacuoles, and
the plasma membrane.
Student Misconceptions and Concerns
1. Students can have trouble relating many cell organelles to their diverse functions. They may not realize that Modules 4.7–4.12 introduce the primary organelles in the general order that they function in the production and release of secretory proteins. Products and information generally move from the central nucleus to the rough ER, through the more peripherally located Golgi apparatus and the secretory vesicles, and finally to the outer plasma membrane. Emphasizing the flow from center to periphery in this process can help students to remember the function of individual organelles as they recall the steps of the sequence.
2. Conceptually, some students seem to benefit from the well-developed cell-factory analogy developed in the text. The use of this analogy in lecture might help to anchor these relationships. As mentioned before, challenge students to find exceptions in the analogy, an exercise that promotes critical thinking.
Teaching Tips
Point out to your students that the endoplasmic reticulum is continuous with the outer nuclear membrane. This explains why the ER is usually found close to the nucleus.
© 2012 Pearson Education, Inc. 27

28. 4.8 The endoplasmic reticulum is a biosynthetic factory
There are two kinds of endoplasmic reticulum—smooth and rough.
Smooth ER
Rough ER
Student Misconceptions and Concerns
1. Students can have trouble relating many cell organelles to their diverse functions. They may not realize that Modules 4.7–4.12 introduce the primary organelles in the general order that they function in the production and release of secretory proteins. Products and information generally move from the central nucleus to the rough ER, through the more peripherally located Golgi apparatus and the secretory vesicles, and finally to the outer plasma membrane. Emphasizing the flow from center to periphery in this process can help students to remember the function of individual organelles as they recall the steps of the sequence.
2. Conceptually, some students seem to benefit from the well-developed cell-factory analogy developed in the text. The use of this analogy in lecture might help to anchor these relationships. As mentioned before, challenge students to find exceptions in the analogy, an exercise that promotes critical thinking.
Teaching Tips
Students often learn that a human body can build up a tolerance to a drug. Here, in Module 4.8, students learn about one of the specific mechanisms of this response. Liver cells exposed to certain toxins or drugs increase the amount of smooth ER, which functions in the processing of these chemicals. Thus, there is a structural and functional explanation to the development of drug tolerance. 28

29. 4.8 The endoplasmic reticulum is a biosynthetic factory
Rough ER makes _____________________
Student Misconceptions and Concerns
1. Students can have trouble relating many cell organelles to their diverse functions. They may not realize that Modules 4.7–4.12 introduce the primary organelles in the general order that they function in the production and release of secretory proteins. Products and information generally move from the central nucleus to the rough ER, through the more peripherally located Golgi apparatus and the secretory vesicles, and finally to the outer plasma membrane. Emphasizing the flow from center to periphery in this process can help students to remember the function of individual organelles as they recall the steps of the sequence.
2. Conceptually, some students seem to benefit from the well-developed cell-factory analogy developed in the text. The use of this analogy in lecture might help to anchor these relationships. As mentioned before, challenge students to find exceptions in the analogy, an exercise that promotes critical thinking.
Teaching Tips
Students often learn that a human body can build up a tolerance to a drug. Here, in Module 4.8, students learn about one of the specific mechanisms of this response. Liver cells exposed to certain toxins or drugs increase the amount of smooth ER, which functions in the processing of these chemicals. Thus, there is a structural and functional explanation to the development of drug tolerance. 29

30. 4.9 The Golgi apparatus finishes, sorts, and ships cell products
Student Misconceptions and Concerns
1. Students can have trouble relating many cell organelles to their diverse functions. They may not realize that Modules 4.7–4.12 introduce the primary organelles in the general order that they function in the production and release of secretory proteins. Products and information generally move from the central nucleus to the rough ER, through the more peripherally located Golgi apparatus and the secretory vesicles, and finally to the outer plasma membrane. Emphasizing the flow from center to periphery in this process can help students to remember the function of individual organelles as they recall the steps of the sequence.
2. Conceptually, some students seem to benefit from the well-developed cell-factory analogy developed in the text. The use of this analogy in lecture might help to anchor these relationships. As mentioned before, challenge students to find exceptions in the analogy, an exercise that promotes critical thinking.
Teaching Tips
1. If you continue the factory analogy, the addition of a molecular tag by the Golgi apparatus is like adding address labels in the shipping department of a factory.
2. Some people think that the Golgi apparatus looks like a stack of pita bread. 30

31. 4.10 Lysosomes are digestive compartments within a cell
A lysosome is a membranous sac containing digestive enzymes.
The enzymes and membrane are produced by the ER and transferred to the Golgi apparatus for processing.
The membrane serves to safely isolate these potent enzymes from the rest of the cell.
Student Misconceptions and Concerns
1. Students can have trouble relating many cell organelles to their diverse functions. They may not realize that Modules 4.7–4.12 introduce the primary organelles in the general order that they function in the production and release of secretory proteins. Products and information generally move from the central nucleus to the rough ER, through the more peripherally located Golgi apparatus and the secretory vesicles, and finally to the outer plasma membrane. Emphasizing the flow from center to periphery in this process can help students to remember the function of individual organelles as they recall the steps of the sequence.
2. Conceptually, some students seem to benefit from the well-developed cell-factory analogy developed in the text. The use of this analogy in lecture might help to anchor these relationships. As mentioned before, challenge students to find exceptions in the analogy, an exercise that promotes critical thinking.
Teaching Tips
1. If you continue the factory analogy, the addition of a molecular tag by the Golgi apparatus is like adding address labels in the shipping department of a factory.
2. Some people think that the Golgi apparatus looks like a stack of pita bread.
© 2012 Pearson Education, Inc. 31

32. 4.10 Lysosomes are digestive compartments within a cell
Lysosomes help digest food particles engulfed by a cell.
A food vacuole binds with a lysosome.
The enzymes in the lysosome digest the food.
The nutrients are then released into the cell.
Lysosomes also help remove or recycle damaged parts of a cell.
Student Misconceptions and Concerns
1. Students can have trouble relating many cell organelles to their diverse functions. They may not realize that Modules 4.7–4.12 introduce the primary organelles in the general order that they function in the production and release of secretory proteins. Products and information generally move from the central nucleus to the rough ER, through the more peripherally located Golgi apparatus and the secretory vesicles, and finally to the outer plasma membrane. Emphasizing the flow from center to periphery in this process can help students to remember the function of individual organelles as they recall the steps of the sequence.
2. Conceptually, some students seem to benefit from the well-developed cell-factory analogy developed in the text. The use of this analogy in lecture might help to anchor these relationships. As mentioned before, challenge students to find exceptions in the analogy, an exercise that promotes critical thinking.
Teaching Tips
As noted in Module 4.10, lysosomes help to recycle damaged cell components. Challenge your students to explain why this is adaptive. Recycling, whether in human society or in our cells, can be an efficient way to reuse materials. The recycled components, which enter the lysosomes in a highly organized form, would require a much greater investment to produce from “scratch.” 32

33. 4.11 Vacuoles function in the general maintenance of the cell
Vacuoles are large vesicles that have a variety of functions.
Some protists have contractile vacuoles that help to eliminate water from the protist.
In plants, vacuoles may
have digestive functions,
contain pigments, or
contain poisons that protect the plant.
Student Misconceptions and Concerns
1. Students can have trouble relating many cell organelles to their diverse functions. They may not realize that Modules 4.7–4.12 introduce the primary organelles in the general order that they function in the production and release of secretory proteins. Products and information generally move from the central nucleus to the rough ER, through the more peripherally located Golgi apparatus and the secretory vesicles, and finally to the outer plasma membrane. Emphasizing the flow from center to periphery in this process can help students to remember the function of individual organelles as they recall the steps of the sequence.
2. Conceptually, some students seem to benefit from the well-developed cell-factory analogy developed in the text. The use of this analogy in lecture might help to anchor these relationships. As mentioned before, challenge students to find exceptions in the analogy, an exercise that promotes critical thinking.
Teaching Tips
Challenge your students to identify animal cell organelles other than mitochondria and chloroplasts that are not involved in the synthesis of proteins. (Lysosomes, vacuoles, and peroxisomes are also not involved in protein synthesis).
© 2012 Pearson Education, Inc. 33

34. Central vacuole Chloroplast Nucleus
Figure 4.11B Central vacuole in a plant cell
Nucleus 34

35. CENTRIOLES A pair of cylinder shaped organelles
Composed of nine tubes, each with three tubules
Involved in cellular division
ONLY in animal cells!

36. 4.13 Mitochondria harvest chemical energy from food
Mitochondria are organelles that carry out cellular respiration in nearly all eukaryotic cells.
Cellular respiration converts the _______ energy in foods to _________ energy in ATP (adenosine triphosphate).
Student Misconceptions and Concerns
Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night.
Teaching Tips
1. ATP functions in cells much like money functions in modern societies. Each holds value that can be generated in one place and spent in another. This analogy has been very helpful for many students.
2. Mitochondria and chloroplasts are each wrapped by multiple membranes. In both organelles, the innermost membranes are the sites of greatest molecular activity and the outer membranes have fewer significant functions. This makes sense when we consider that the outer membranes correspond to the plasma membrane of the eukaryotic cells that originally wrapped the free-living prokaryotes during endocytosis. Biology makes sense in light of evolution.
© 2012 Pearson Education, Inc. 36

37. 4.13 Mitochondria harvest chemical energy from food
Mitochondria have two internal compartments.
The intermembrane space is the narrow region between the inner and outer membranes.
The mitochondrial matrix contains
the mitochondrial DNA,
ribosomes, and
many enzymes that catalyze some of the reactions of cellular respiration.
Student Misconceptions and Concerns
Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night.
Teaching Tips
1. ATP functions in cells much like money functions in modern societies. Each holds value that can be generated in one place and spent in another. This analogy has been very helpful for many students.
2. Mitochondria and chloroplasts are each wrapped by multiple membranes. In both organelles, the innermost membranes are the sites of greatest molecular activity and the outer membranes have fewer significant functions. This makes sense when we consider that the outer membranes correspond to the plasma membrane of the eukaryotic cells that originally wrapped the free-living prokaryotes during endocytosis. Biology makes sense in light of evolution. 37

38. 4.14 Chloroplasts convert solar energy to chemical energy
Chloroplasts are the photosynthesizing organelles of all photosynthesizing eukaryotes.
Photosynthesis is the conversion of _____ energy from the sun to the _________ energy of sugar molecules.
Student Misconceptions and Concerns
Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night.
Teaching Tips
Mitochondria and chloroplasts are each wrapped by multiple membranes. In both organelles, the innermost membranes are the sites of greatest molecular activity and the outer membranes have fewer significant functions. This makes sense when we consider that the outer membranes correspond to the plasma membrane of the eukaryotic cells that originally wrapped the free-living prokaryotes during endocytosis. Biology makes sense in light of evolution. 38

39. 4.14 Chloroplasts convert solar energy to chemical energy
Chloroplasts are partitioned into compartments.
Between the outer and inner membrane is a thin intermembrane space.
Inside the inner membrane is
a thick fluid called ____________ that contains the chloroplast DNA, ribosomes, and many enzymes and
a network of interconnected sacs called ________________.
In some regions, thylakoids are stacked like poker chips. Each stack is called a ______________,where green chlorophyll molecules trap solar energy.
Student Misconceptions and Concerns
Students often mistakenly think that chloroplasts are a substitute for mitochondria in plant cells. They might think that cells either have mitochondria or they have chloroplasts. You might challenge this thinking by asking how plant cells generate ATP at night.
Teaching Tips
Mitochondria and chloroplasts are each wrapped by multiple membranes. In both organelles, the innermost membranes are the sites of greatest molecular activity and the outer membranes have fewer significant functions. This makes sense when we consider that the outer membranes correspond to the plasma membrane of the eukaryotic cells that originally wrapped the free-living prokaryotes during endocytosis. Biology makes sense in light of evolution.
© 2012 Pearson Education, Inc. 39

40. 4.16 The cell’s internal skeleton helps organize its structure and activities
Cells contain a network of protein fibers, called the _________________________, which functions in structural support and motility.
Cilia and flagella are made of microtubules (one type of fiber making up the cytoskeleton)
While some protists have flagella and cilia that are important in locomotion, some cells of multicellular organisms have them for different reasons.
Cells that sweep mucus out of our lungs have cilia.
Animal sperm are flagellated.
Student Misconceptions and Concerns
Students often regard the fluid of the cytoplasm as little more than cell broth, a watery fluid that suspends the organelles. The diverse functions of thin, thick, and intermediate filaments are rarely appreciated before college. Module 4.16 describes the dynamic and diverse functions of the cytoskeleton.
Teaching Tips
Analogies between the infrastructure of human buildings and the cytoskeleton are limited by the dynamic nature of the cytoskeleton. Few human structures have a structural framework that is routinely constructed, deconstructed, and then reconstructed in a new configuration on a regular basis. (Tents are often constructed, deconstructed, and then reconstructed repeatedly, but typically rely upon the same basic design.) Thus, caution is especially warranted when using such analogies.
© 2012 Pearson Education, Inc. 40

41. Cilia
Figure 4.17A Cilia on cell lining the respiratory tract 41

42. 4.17 Cilia and flagella move when microtubules bend
Both flagella and cilia are made of microtubules wrapped in an extension of the plasma membrane.
A ring of nine microtubule doublets surrounds a central pair of microtubules. This arrangement is
called the pattern and
anchored in a basal body with nine microtubule triplets arranged in a ring.
Student Misconceptions and Concerns
Students often think that the cilia on the cells lining our trachea function like a comb, removing debris from the air. Except in cases of disease or damage, these respiratory cilia are covered by mucus. Cilia do not reach the air to comb it free of debris. Instead, these cilia sweep dirty mucus up our respiratory tracts to be expelled or swallowed.
Teaching Tips
Students might enjoy this brief class activity. Have everyone in the class clear their throats at the same time. Wait a few seconds. Have them notice that after clearing, they swallowed. The mucus that trapped debris is swept up the trachea by cilia. When we clear our throats, this dirty mucus is disposed of down our esophagus and among the strong acids of our stomach!
© 2012 Pearson Education, Inc. 42

43. Outer microtubule doublet
Figure 4.17C
Outer microtubule doublet
Central microtubules
Radial spoke
Dynein proteins
Figure 4.17C Structure of a eukaryotic flagellum or cilium
Plasma membrane 43

44. 4.19 The extracellular matrix of animal cells functions in support and regulation
Animal cells synthesize and secrete an elaborate extracellular matrix (ECM) that
helps hold cells together in tissues and
protects and supports the plasma membrane.
Outside cell
Student Misconceptions and Concerns
The structure and functions of the extracellular matrix (ECM) are closely associated with the cells that it contacts. Students might suspect that like roots from a tree, cells are anchored to the matrix indefinitely. However, some cells can detach from the ECM and migrate great distances, often following molecular trails (such as fibronectin and laminin) that direct them along the journey.
Teaching Tips
The extracellular matrix forms a significant structural component of many connective tissues, including cartilage and bone. Many of the properties of cartilage and bone are directly related to the large quantities of material sandwiched between the bone (osteocyte) and cartilage (chondrocyte) cells.
Glycoprotein complex
Collagen fibers
Integrin (membrane proteins)
Inside cell 44

45. 4.20 Three types of cell junctions are found in animal tissues
Adjacent cells communicate, interact, and adhere through specialized junctions between them.
Tight junctions
Anchoring junctions
Gap junctions
Teaching Tips
Tight junctions form a seal that prevents the movement of fluids past the region of the junction. Functionally, this is similar to the lengthy zipper-like seal at the top of common plastic food storage bags. 45

46. 4.21 Cell walls enclose and support plant cells
A plant cell, but not an animal cell, has a rigid cell wall that
protects and provides skeletal support that helps keep the plant upright against gravity and
is primarily composed of cellulose.
Plant cells have cell junctions called plasmodesmata that serve in communication between cells.
Teaching Tips
1. Consider challenging your students to suggest analogies to the structure and function of plasmodesmata (perhaps air ducts between offices in a building). Consider discussing the advantages of interconnected cytoplasms.
2. The text in Module 4.21 compares the fibers-in-a-matrix construction of a plant cell wall to fiberglass. Students familiar with highway construction or the pouring of concrete might also be familiar with the frequent use of reinforcing bar (rebar) to similarly reinforce concrete.
© 2012 Pearson Education, Inc. 46

47. Plant cell walls Vacuole Plasmodesmata Primary cell wall
Figure 4.21
Plant cell walls
Vacuole
Plasmodesmata
Primary cell wall
Secondary cell wall
Figure 4.21 Plant cell walls and plasmodesmata
Plasma membrane
Cytoplasm 47

48. 4.22 Review: Eukaryotic cell structures can be grouped on the basis of four basic functions
Eukaryotic cell structures can be grouped on the basis of four functions:
genetic control,
manufacturing, distribution, and breakdown,
energy processing, and
structural support, movement, and communication between cells.
Teaching Tips
1. The chapter ends noting the three fundamental features of all organisms. Challenge students to explain if viruses are organisms according to this definition.
2. Some students might benefit by creating a concept map integrating the information in Table Such a map would note the components of a cell interconnected by lines and relationships between these cellular components. Such techniques may also be beneficial in later chapters, depending upon the learning style of particular students.
© 2012 Pearson Education, Inc. 48

49. Table 4.22
Table 4.22 Eukaryotic Cell Structures and Functions 49

50. 4.15 EVOLUTION CONNECTION: Mitochondria and chloroplasts evolved by endosymbiosis
Mitochondria and chloroplasts have
DNA and
ribosomes.
The structure of this DNA and these ribosomes is very similar to that found in prokaryotic cells.
The endosymbiont theory proposes that mitochondria and chloroplasts were formerly small prokaryotes and they began living within larger cells.
Student Misconceptions and Concerns
The evidence that mitochondria and chloroplasts evolved from free-living prokaryotes is further supported by the small size of these organelles, similar to the size of a prokaryote. Mitochondria and chloroplasts are therefore helpful in comparing the general size of eukaryotic and prokaryotic cells. You might think of these organelles as built-in comparisons.
Teaching Tips
1. Mitochondria and chloroplasts are not cellular structures that are synthesized in a cell like ribosomes and lysosomes. Instead, mitochondria only come from other mitochondria and chloroplasts only come from other chloroplasts. This is further evidence of the independent evolution of these organelles from free-living ancestral forms.
2. Mitochondria and chloroplasts are each wrapped by multiple membranes. In both organelles, the innermost membranes are the sites of greatest molecular activity and the outer membranes have fewer significant functions. This makes sense when we consider that the outer membranes correspond to the plasma membrane of the eukaryotic cells that originally wrapped the free-living prokaryotes during endocytosis. Biology makes sense in light of evolution.
© 201 Pearson Education, Inc. 50

51. Endoplasmic reticulum
Figure 4.15
Mitochondrion
Nucleus
Endoplasmic reticulum
Engulfing of photosynthetic prokaryote
Some cells
Engulfing of oxygen- using prokaryote
Chloroplast
Host cell
Figure 4.15 Endosymbiotic origin of mitochondria and chloroplasts
Mitochondrion
Host cell 51

52. Endosymbiosis

53. You should now be able to
Distinguish between the 3 types of microscopes.
State the two parts of cell theory.
Distinguish between the structures of prokaryotic and eukaryotic cells.
Explain how cell size is limited and why surface area to volume ratio is important.
Describe the structure and functions of cell membranes.
© 2012 Pearson Education, Inc. 53

54. You should now be able to
Compare the structures of plant and animal cells. Note the function of each cell part. Be able to label a diagram.
Compare the structures and functions of chloroplasts and mitochondria.
Describe the evidence that suggests that mitochondria and chloroplasts evolved by endosymbiosis.
Describe the structure and function of cilia and flagella.
© 2012 Pearson Education, Inc. 54

55. You should now be able to
Compare the structures and functions of tight junctions, anchoring junctions, and gap junctions.
Relate the structures of plant cell walls and plasmodesmata to their functions.
Describe the four functional categories of organelles in eukaryotic cells.
© 2012 Pearson Education, Inc. 55

57. Internet Sites http://www.phschool.com/science/biology_place/
(select Biocoach; Cell structures and function)

58. What type of cell? Label Also Identify: cytoplasm, ribosomes (gold)
Figure 4.UN02
What type of cell?
Label
(gold)
(red)
Also Identify: cytoplasm,
ribosomes
(blue)
Figure 4.UN02 Reviewing the Concepts, 4.3 58

59. Name organelles…. 1 2 8 3 7 6 4 5

60. a. l. b. c. k. j. i. h. d. g. e. f. Figure 4.UN03
Figure 4.UN03 Connecting the Concepts, question 1 h. d. g. e. f. 60