Part I
1. In your everyday life, you have probably noticed that certain instruments are ideal for certain situations. For example, you would use a spoon rather than a fork to eat soup because a spoon is shaped for scooping, while soup would slip between the tines of a fork. The use of ideal instruments also applies in science. In what situation(s) would the use of a light microscope be ideal, and why?
2. In what situation(s) would the use of a scanning electron microscope be ideal, and why?
3. In what situation(s) would a transmission electron microscope be ideal, and why?
4. What are the advantages and disadvantages of each of these types of microscopes?
Show Selected Answers
1. A light microscope would be ideal when viewing a small living organism, especially when the cell has been stained to reveal details.
2. A scanning electron microscope would be ideal when you want to view the minute details of a cell’s surface, because its beam of electrons moves back and forth over the surface to convey the image.
3. A transmission electron microscope would be ideal for viewing the cell’s internal structures, because many of the internal structures have membranes that are not visible by the light microscope.
4. The advantages of light microscopes are that they are easily obtained, and the light beam does not kill the cells. However, typical light microscopes are somewhat limited in the amount of detail they can reveal. Electron microscopes are ideal because you can view intricate details, but they are bulky and costly, and preparation for the microscopic examination kills the specimen.
Part II
1. Antibiotics are medicines that are used to fight bacterial infections. These medicines kill prokaryotic cells without harming human cells. What part or parts of the bacterial cell do you think antibiotics target? Why?
2. Explain why not all microbes are harmful:
Show Selected Answers
1. The cell wall would be targeted by antibiotics as well as the bacteria’s ability to replicate. This would inhibit the bacteria’s ability to reproduce, and it would compromise its defense mechanisms.
2. Some microbes are beneficial. For instance, E. coli bacteria populate the human gut and help break down fiber in the diet. Some foods such as yogurt are formed by bacteria.
Part III
1. You already know that ribosomes are abundant in red blood cells. In what other cells of the body would you find them in great abundance? Why?
2. What are the structural and functional similarities and differences between mitochondria and chloroplasts?
3. List the organelles of an eukaryotic cell and describe their functions:
Show Selected Answers
1. Ribosomes are abundant in muscle cells as well because muscle cells are constructed of the proteins made by the ribosomes.
2. Both are similar in that they are enveloped in a double membrane, both have an intermembrane space, and both make ATP. Both mitochondria and chloroplasts have DNA, and mitochondria have inner folds called cristae and a matrix, while chloroplasts have chlorophyll and accessory pigments in the thylakoids that form stacks (grana) and a stroma.
Part IV
1. In the context of cell biology, what do we mean by form follows function? What are at least two examples of this concept?
2. In your opinion, is the nuclear membrane part of the endomembrane system? Why or why not? Defend your answer:
Show Selected Answers
1. “Form follows function” refers to the idea that the function of a body part dictates the form of that body part. As an example, compare your arm to a bat’s wing. While the bones of the two correspond, the parts serve different functions in each organism and their forms have adapted to follow that function.
2. Since the external surface of the nuclear membrane is continuous with the rough endoplasmic reticulum, which is part of the endomembrane system, then it is correct to say that it is part of the system.
Part V
1. What are the similarities and differences between the structures of centrioles and flagella?
2. How do cilia and flagella differ?
Show Selected Answers
1. Centrioles and flagella are alike in that they are made up of microtubules. In centrioles, two rings of nine microtubule “triplets” are arranged at right angles to one another. This arrangement does not occur in flagella.
2. Cilia and flagella are alike in that they are made up of microtubules. Cilia are short, hair-like structures that exist in large numbers and usually cover the entire surface of the plasma membrane. Flagella, in contrast, are long, hair-like structures; when flagella are present, a cell has just one or two.
