The Literature of Plant Species

Problem Set 1 Solutions:
Chapters 1
1 Cell sizes: E. coli is a cylindrical bacteria with 1 M wide and 2 M long. Liver cells are approximately spherical with a diameter of 20 M. Plant palisade cells are cylinders 20 M wide and 35 M long.
A) Calculate the volumes of each cells?
A) Since E.Coli is cylindrical
Volume of a cylinder = r2h, where r is half of bacterial width/diameter = 1M/2 = 0.5M and h is the length of the bacteria = *(0.5)22 = 1.57 M3
B) Since liver cells are spherical
Volume of a sphere = 4/3r3 (Radius of liver cell = 20 M/2 = 10 M) 4/3*4187 M3
C) Volume of cylindrical palisade cells = r2h = *(10)235 = 10990 M3
B) How many E Coli will fit inside the human liver cells?
# of E. Coli that can fit in liver cells = Volume of Liver Cells/Volume of E Coli = 4187 M3/1.57 M3 = 2666 E. Coli
C) How many liver cells will fit inside the palisade cells?
# of liver cells that can fit in palisade cells = Volume of Palisade Cells/Volume of Liver Cells = 10990 M3/ 4187 M3 = 2 Liver Cells

2) . If a typical membrane is 8 nm wide, how many such membranes would have to be aligned up to see in a light microscope? How many with an electron microscope?
i) Resolution/resolving power of light microscope = 0.2 nM = 200 nM
# Membranes need to be aligned to be seen by light microscope = 200 nM/8 nM = 25 membranes ii) Resolution/resolving power of electron microscope = 2 nM
Therefore, a single membrane will be visible 3) Human ribosomes are roughly spherical and have a diameter of 30 nm.
How many ribosomes would fit in a human liver cell (from problem 1)?
Volume of ribosome (spherical) = 4/3r3 , R
Radius of a ribosome = 30 nm/2 = 15 nM or 0.015 nM
= 4/3*1.413x10-5 nM3
# of ribosomes that can fit in a liver cells = volume of liver cells (from 1.2)/volume of ribosomes = 4187 nM3 / 1.413x10-5 nM3 = 2.96x108 ribosomes 4) E coli DNA is 2 nm wide by 1.36 mm long. What percentage of the cell is filled with DNA? (from problem 1.2a)
Volume of E.Coli DNA (=volume of a cylinder) = r2h
Radius of E coli DNA = 2/2 nm =(2/2)/1000 M = 0.001 M
Length of E Coli DNA = 1.36 mm = 1.36*1000 M = 1360 M
Therefore, volume of DNA = *(0.001)21360 = 4.27x10-3 M3
% of E.Coli filled with DNA = (Volume of E.Coli DNA/Volume of E.Coli)*100 = (4.27x10-3 nM3/1.57 M3)*100 = 0.27% of the cell 5) Facts of Life
In each of the following, indicate why the statement was considered once TRUE and it is no longer considered a FACT. Plant and animal tissues are considered different because animal tissues do not have conspicuous boundaries that divide the cell
Initially thought to be true because animal cells do not have cell walls, which made it difficult for early investigators to identify individual cells using the crude microscope available during that time. Schwann (1839) shown that this was incorrect for cartilage cells, which have well defined boundaries of collagen fibers, and later extended to all animal cells.
B. Living organisms are not governed by the laws of chemistry and physics, but are subject to a “vital force” that is responsible for the formation of organic compounds.
Initially thought to be true because living organisms seems to increase in complexity spontaneously. Synthesis of urea, an organic compound made by all living cells from an inorganic compound by Wohler (1828) finally disproved this concept.
C. Hereditary materials are of proteins but not DNA, because DNA contains only four nucleotides as monomers
Originally thought to be true because tetranucleoide in DNA was not complex enough to encode hereditary factors.
D. The fermentation of sugar to alcohol can take place only in the presence of yeast cells
Initially thought to be true, because of the demonstration by Pasteur that yeast cells were needed for alcoholic fermentation. Later Buchner and Buchner (1897) showed that extracts from yeast cells could substitute for intact cells, an effect which we know now is due to the presence of enzymes that catalyze various steps in fermenting reaction.
E) The flow of genetic information in a cell is always from DNA to RNA to protein.
Initially thought to be true, however, discovery of the process of reverse transcription demonstrated that in retroviruses genetic information flows from RNA to DNA.
F) DNA always exists as a duplex of two strands wound together into a right-handed helix.
Initially thought to be true that right-handed helix is the only form of DNA, later on it was discovered the right handed form of DNA as well as single stranded DNA.
G) The genetic code specifying how the information present in the DNA molecule is used to make proteins is universal in the sense that all organisms use the same code.
Genetic code is not universal. In some prokaryotes codons encode different amino acids.
Q6: The following paragraph describes the activities of hypothetical scientists. After reading this paragraph, list the steps of the scientific method, and list the activities that correspond to the steps of the scientific method. A rancher noticed that several grazing animals had become sick after grazing in a new area. The rancher asked a team of scientists to analyze this problem. They visited the area and found that the food available to the animals was similar to the food they had been eating. The water supply in the area was adequate but limited to a single spring. Some of the scientists felt that the water might be contaminated with a pathogen. Therefore, they collected water samples from the spring in the new area and compared them with water samples taken from previous grazing sites. The scientists noticed that water from the new area was cloudier than water obtained from other areas. Culturing this water revealed that a pathogenic strain of bacteria was present. This bacterial strain was found to be identical to a strain obtained from sick animals. This strain was not present in healthy animals. They concluded that a contaminated water supply in the new area was responsible for the problem and instructed the rancher to avoid the water supply. The disease was not found in the rancher's livestock again.
Observation: The rancher and the scientists made initial observation regarding the food and water that the livestock consumed
Hypothesis: The water supply was contaminated with a pathogen
Experimentation: Water was collected, examined and cultured
Interpret Results: The data was compared to other water samples. The cultures were compared to those obtained from livestock.
Draw conclusion: The water was contaminated and responsible for outbreak.

Q7: Scientific discoveries change the course of human history. The people who make these discoveries and the circumstances that surround these discoveries are very important to our understanding and appreciation of science. Can you identify the individuals as they might have described themselves?
A) I am a seventeenth century shopkeeper from Holland. My hobby involves hand-polishing glass to make lenses, some of which can magnify almost 300-fold. I was the first to observe living cells and am known as the "Father of Microbiology.
Anton van Leeewenhoek
B) I was the Curator of Instruments for the Royal Society of London in 1665. I developed a crude microscope that could magnify around 30-fold. I examined plant material and observed many small chambers that I called cellulae.
Robert Hooke
C) At the University of California, Berkeley, I worked with radioisotopes. In the late 1940s and early 1950s, I used carbon-14 to identify the most common pathway for photosynthetic carbon metabolism.
Melvin Calvin
D) We worked out the double helix model of DNA structure in 1953. We later received the Nobel Prize for this work.
Watson & Crick
E) I am a nineteenth century German chemist. By synthesizing an organic molecule from inorganic components, I dispelled the idea that biological processes were exempt from the laws of chemistry.
Wohler
F) My colleague and I worked with bacterial viruses. We were able to demonstrate that DNA–not protein–was the genetic material of the cell.
Hershey & Chase
G) I am a Swedish scientist. I developed the ultracentrifuge to determine sedimentation rates of proteins. The ultracentrifuge was later used to isolate subcellular fractions.
Svedberg
Q8. What is the advantage having microvilli in the intestine? What would happen to an individual that lacks microvilli as a result of an inherited mutation?
Microvilli increase the surface area/volume ratio of intestine to increase the efficiency and effectiveness of nutrient absorption. Lack of microvilli reduce the nutrient absorption capacity of intestine and result in diseases associated with nutrient deficiency.
Q9. Recently there have been many claims concerning the health benefits of green tea. Suppose you read a claim that claims drinking green tea causes weight loss. You are provided with the following information about the studies that led to this claim People were weighed at the beginning of the study People were asked to drink two cups of green tea every day for 6 weeks. People were weighed at the end of the study People who drank green tea for 6 weeks lost some weight by the end of the study It was concluded that green tea is helpful for weight loss
This study has some holes in its design. Assuming no information other than that provided above, indicate at least four things that could be done to improve the experimental design.
1) Add a control group
2) Extend the test for a longer period of time
3) Randomize the subjects to make sure that other variables such as eating habits, geneder, age, race etc. are responsible for the weight loss.
4) Repeat the study Q10. On TV you may have seen advertisements in which beautiful people with clear skin claiming a specific skin care product is “scientifically proven” to reduce acne, which gave them their glowing clear skin
A) Is these testimony itself is enough evidence for you to try these products? Why or why not?
No, the testimony could be anecdotal evidence or a paid advertisement.
B) What scientific evidence would convince you to buy this product? Explain your answer.
Several peer reviewed publication showing the results of a well-controlled clinical trial.