CHAPTER 1 TEXTBOOK

Explain why each of the following statements is false. Because of the wavelength of light, resolution of cellular structures smaller than 200nm can never be achieved

this is false because electron microscopes would be able to see structures this small

Explain why each of the following statements is false. The best way to carry out a scientific experiment is to try to prove a hypothesis by varying all the relevant conditions.

this is false because if you change all of the conditions, you will not know which condition is truly affecting the experiment.

Explain why each of the following statements is false. Fluorescence microscopy can allow us to visualize cells but cannot help identify them

this is false because it can enable us to detect specific proteins, DNA sequences and other molecules which would allow us to identify them.

Explain why each of the following statements is false. Because all DNA molecules have similar chemical composition, it is not possible to separate and characterize individual DNA molecules

this is untrue because although the molecules are similar, they are not the exact same so we can decipher between them.

Each of the statements were once though to be a biological fact but are not deemed untrue. For each, indicate why the statement was once thought to be true and why it is no longer considered a fact. Plant and animal tissues are constructed quite differently because animal tissues do not have conspicuous boundaries that divide them into cells

this is untrue because animal cells are divided by a cell membrane which is also included in plant cells.

Assume that the unaided human eye has a limit of resolution of about .25 mm and that a modern light microscope has a useful magnification of about 1000x. b. What are the approximate diameters of the smallest structure that Hooke would have been able to observe with his microscope? Would he have been able to see any of the structures in Figure 1-4? Why or why not?

~ He would not have been able to see them because all of the structures are in micrometers which cannot be seen with only 30x magnification.

Indicate the members of each pair as beloning to cytological, biochemical, or genetic strand of cell biology. Suggest one advantage to the second technique to the first. Centrifugation/ultracentrifugation

B; ultracentrifugation can separate and isolate smaller subcellular structures and macromolecules than centrifugation.

Indicate the members of each pair as beloning to cytological, biochemical, or genetic strand of cell biology. Suggest one advantage to the second technique to the first. Chromatography/electrophoresis

B; uses an electrical field to separate macromolecules based on their mobility through a semisolid gel

Indicate the members of each pair as beloning to cytological, biochemical, or genetic strand of cell biology. Suggest one advantage to the second technique to the first. Transmission electron microscopy/scanning electron microscopy

C; SEM scans the surface of a specimen and forms an image by detecting electrons that are deflected from its outer surface rather than detecting electrons that are transmitted though the specimen.

Indicate the members of each pair as beloning to cytological, biochemical, or genetic strand of cell biology. Suggest one advantage to the second technique to the first. Light microscope/electron microscope

C; the electron microscope uses a bean of electrons rather than visible light which magnifies objects much more, allowing us to see even smaller structures.

Indicate the members of each pair as beloning to cytological, biochemical, or genetic strand of cell biology. Suggest one advantage to the second technique to the first. Sequencing of a genome/bioinformatics

G; combines biology and a computer in order to make a sequence of data

Indicate the members of each pair as beloning to cytological, biochemical, or genetic strand of cell biology. Suggest one advantage to the second technique to the first. Cell cultures/model organisms

G; model organisms are easy to manipulate, and widely studied, making them useful or experimental studies.

Each of the statements were once though to be a biological fact but are not deemed untrue. For each, indicate why the statement was once thought to be true and why it is no longer considered a fact. Living organisms are not governed by the laws of chemistry and physics, as is nonliving matter, but are subject to different laws that are responsible for the formation of organic compounds

this is untrue because cells are living things so therefore are governed by chemistry and physics

Explain why each of the following statements is false. The flow of genetic information is always from DNA to RNA to protein.

this is untrue because sometimes it is just from RNA to protein and sometimes RNA must be reversed transcribed back to DNA.

Each of the statements were once though to be a biological fact but are not deemed untrue. For each, indicate why the statement was once thought to be true and why it is no longer considered a fact. Genes are most likely consistent of proteins because the only other likely candidate, DNA, is a relatively uninteresting molecule consisting of only four kinds of monomers (nucleotides) arranged in a relatively repetitive sequence.

this is untrue because there are an infinite number of sequences that can make up DNA/genes

Each of the statements were once though to be a biological fact but are not deemed untrue. For each, indicate why the statement was once thought to be true and why it is no longer considered a fact. The fermentation of sugar to alcohol can take place only if living yeast cells are present.

this is untrue because yeast cells die during fermentation

The genetic material of the E-coli cell is the problem above consists of a circular DNA molecule with a strand diameter of 2 nanometers and a total length of 1.36 mm. to be accommodated in a cell that is only a few micrometers long, this DNA molecule is tightly coiled and folded into a nucleoid that occupies a small portion of the cell's internal volume. Approximating the DNA molecule as a very thin cylinder, calculate the smallest possible volume the DNA molecule could fit into, and express is as a percentage of the internal volume of the bacterial cell that would calculate in the first problem.

~ 0.27%

E-coli is a cylindrical shape, with a diameter of about 1 micrometer and a length of about 2 micrometers. A human liver cell is roughly spherical and has a diameter of about 20 micrometers. A columnar palisade cell has a diameter of about 20 micrometers and a length of about 35 micrometers c. Approximately how many liver cells would fit inside a palisade cell?

~ About 2.6 of them

E-coli is a cylindrical shape, with a diameter of about 1 micrometer and a length of about 2 micrometers. A human liver cell is roughly spherical and has a diameter of about 20 micrometers. A columnar palisade cell has a diameter of about 20 micrometers and a length of about 35 micrometers b. Approximately how many bacterial cells would fit in the internal volume of a human liver cell?

~ About 2667 of them

E-coli is a cylindrical shape, with a diameter of about 1 micrometer and a length of about 2 micrometers. A human liver cell is roughly spherical and has a diameter of about 20 micrometers. A columnar palisade cell has a diameter of about 20 micrometers and a length of about 35 micrometers a. Calculate the approximate volume of each of these three cell types in cubic micrometers (V=pr2h for a cylinder and V=4pr3/3 for a sphere)

~ E-coli = 1.57 cubic micrometers, liver cell = 4189 cubic micrometers, palisade cell = 10996 cubic micrometers

Assume that the unaided human eye has a limit of resolution of about .25 mm and that a modern light microscope has a useful magnification of about 1000x. a. Define limit of resolution of Hooke's microscope? What about van Leeuwenhoek's microscope?

~ H = 30x and vL = 300x

All cells and many subcellular structure are surrounded by membrane. Assuming a typical membrane to be about 8 nanometers wide, how many such membranes would have to be aligned side by side before the structure could be seen with a light microscope? How many with an electron microscope?

~ You would have to stack 25 of them to see it in a light microscope and only one for an electron microscope

Ribosomes are the cell structures in which the process of protein synthesis takes place. A human ribosome is roughly spherical structure with a diameter of about 30 nanometers. How many ribosomes would fit in the internal volume of the human liver cell described in the problem above if the entire volume of the cell were filled with ribosomes?

~ about 300000001 ribosomes would fit

Assume that the unaided human eye has a limit of resolution of about .25 mm and that a modern light microscope has a useful magnification of about 1000x. c. What are the approximate dimensions of the smallest structure that van Leeuwenhoek would have been able to observe with his microscope? Would he have been able to observe and of the structures with his microscope?

~ his microscope could see around 1 micrometer, so he would have been able to see the plant cell and the animal cell, their nuclei, chloroplasts, and their mitochondria. He would have been able to see a bacterium as well.

Assume that the unaided human eye has a limit of resolution of about .25 mm and that a modern light microscope has a useful magnification of about 1000x. d. What are the approximate dimensions of the smallest structure that the contemporary cell biologist should be able to observe with a modern light microscope?

~ they would be able to see a bacterium

Assume that the unaided human eye has a limit of resolution of about .25 mm and that a modern light microscope has a useful magnification of about 1000x. e. Consider the eight structures shown in the figure. Which of these structures would both hooke and van leeuwenhowk have been able to see in their microscopes? Which, if any that either hooke nor van L could see?

~ they would both be able to see the whole cells, but only van L would be able to see any of the organelles