Name__________________________
Mini-Exam I
Biology 140
Summer 2020
Answer questions I, II, and III. Answer all parts of questions I and II. Note that you have a choice between answering question A OR question B for question III.
Your answers should be concise and focused but also complete. Some questions may be answered with a single word, and all responses should be under 300 words.
Your answers must be in your own words; direct quotes are prohibited and will result in the loss of points.
You will be graded based on accuracy and completeness; additionally, you must demonstrate a thorough understanding of the concepts and be able to analyze the information and apply your knowledge when answering the questions. Extra material that does not directly address the question will not earn you points and may cause you to lose points if incorrect.
You may answer your question directly on the document using your computer, or you may adjust the space between answers, print out the exam, write the answers by hand, scan or photograph your exam. To hand in your exam, upload it to Canvas (it is listed as an assignment, but it is an exam).
The exam will be open for 48 hours. You may take as long as you would like to work on the exam during that 48-hour window, but it is expected that it will only take a few hours to complete it. The exam does not need to be completed in one sitting.
The exam is an open resource, meaning that you may use books and the internet to answer the questions; however, you must write the answers in your own words, and it is recommended that you use Turnitin before submitting your responses.
You may not receive or give help to anyone during the exam, and you may not communicate with other students about the exam until after the 48-hour window closes.
Sign or type your name after reading the instructions:
I have read and agree to follow these instructions.
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- (18 points) You are at home watching Ancient Aliens when a small meteorite falls from the sky, breaking open upon impact. Being a biologist, you know that certain organic molecules have been found inside the gas spaces within meteorites. You don your personal protection equipment and go outside to have a look. It appears to be an interesting rock, and you collect some samples to study in your lab. As the days go by, you notice changes in the plants, insects, and other animals around the site where the meteorite hit the ground.
After several months of study, you find that there is a life form that produces an enzyme that changes hydrogen bonds to covalent bonds.
- Choose one of the four macromolecules found in living organisms. Which one did you choose?
Nucleic Acid
- Explain the role of hydrogen bonds in the macromolecule you have chosen and how the hydrogen bonds contribute to the structure of the macromolecule.
The hydrogen bond holds complementary strands of DNA together. As a result of the position and availability of hydrogen bond donor nucleotides pair precisely. Cytosine complements perfectly with guanine by three hydrogen bonds
- Explain what effect the enzyme that changes hydrogen bonds to covalent bonds would have on the structure of the macromolecule you chose.
Conversion of a hydrogen bond to covalent bond in a nucleic acid refers to dissociating the respective strands during replication this is facilitated by a messenger RNA from a virus that stimulates the ribosomes to produce hydrolase enzyme
- Explain what effect the enzyme that changes hydrogen bonds to covalent bonds would have on the function of the macromolecule you chose.
A change in hydrogen bond implies that a shift in the positions of the nucleotides as a result of the change in electrostatic property causes thymine in a DNA to lose its donor electron; therefore, it pairs with guanine, resulting to a translocation mutation.
- Explain how the change from hydrogen bonds to covalent bonds would affect the organism at the cell and whole-organism levels.
This result in gene mutation whereby complex molecules such as hemoglobin or chloroplast can be produced but they are missing an essential component to make them completely functional (emergent property.)
- Describe the visible changes you may have observed in the plants, insects, and other animals around the site where the meteorite hit the ground.
- (21 points) Read the information about cystic fibrosis below and CHOOSE ONE of the following course themes:
- Emergent properties
- Structure/function relationships
After reading the information about cystic fibrosis, briefly answer all three of the following questions for the theme you have chosen.
Cystic fibrosis (CF) is an inherited disease. The mutated form of the gene found in CF patients results in changes in the structure of the cystic fibrosis transmembrane conductance regulator (CFTR) protein in these patients. This protein is responsible for transporting ions and water in and out of the cell, through the cellular membrane. Mutations in the CTFR gene may result in CTFR proteins that don’t function well. Other mutations in the CTFR gene may result in a reduced number of CTFR proteins in the cell membrane.
In individuals with CTFR mutations, ion transport is reduced and water is retained in the cells. The reduced export of water causes the mucus in the respiratory tract to become very thick, preventing the clearing of bacteria and particles from the lungs and leading to infections and poor lung function. Other organs, including those in the digestive tract, may also be affected.
CFTR proteins in a person without CF
In a person without CF, the cell produces CFTR proteins that work correctly. At the cell surface, the proteins act as channels between the inside and outside of the cells. These channels open and close to allow water and particles such as chloride ions to flow into or out of the cells. This helps the body maintain a healthy balance of salt and water.
CFTR proteins in a person with CF
In a person with CF, there are either too few CFTR proteins at the cell surface, CFTR proteins at the cell surface that don’t work correctly, or both.
CFTR proteins not working correctly:
As a result, water and salt can’t flow freely into or out of the cells like they should. This reduced water and salt flow can eventually lead to thick, sticky mucus building up in the lungs and other parts of the body, as well as other symptoms of CF.
- In your own words, define the theme you have chosen.
Emergent property refers to a phenomenon or property which a complex system or molecules has or perform but the individual members of the complex system don’t have the property
- Explain how cystic fibrosis illustrates the theme you chose.
Cystic fibrosis exhibits emergent property; a person with CF has the protein CFTR; however, they are not regulating the uptake of chloride ions, or their number is very few to be of any significance.
- Using the same theme, explain how Sickle Cell Disease illustrates the theme you chose.
Individuals with sickle cell anemia have the same concentration of erythrocytes like normal individuals, however, the shape of the erythrocyte does not provide enough surface area for uptake of oxygen
III. (11 points) Choose ONE of the prompts below (A or B) and answer both of the questions (1 and 2) for that prompt thoroughly. If you answer more than one prompt, only the first will be graded (only A will be graded if you have answered it, whether or not you have also answered B).
Answer question A OR question B.
- Discuss the chemical structure and properties of water molecules and explain why water makes a good solvent in living cells.
- Include a description of the molecular make-up of water molecules and the contributions of intermolecular (between molecules) and intramolecular (within a molecule) bonds in your discussion. You may use diagrams or sketches to illustrate your points.
Water is a simple molecule that consists of one oxygen atom bonded to two hydrogen atoms by strong covalent bonds. The hydrogen ions are positively charged while the oxygen atom is negatively charged because of the high electronegativity of the oxygen atom, the electron shared by the oxygen and hydrogen is repelled, resulting to bonds that are polar covalent (hydrogen bonds). As a result of this attraction, oxygen atom acquires a partial negative (-δ) while the hydrogen atom acquires a partial positive (+δ; the resulting structure is bent because of the two lone electrons in the oxygen atom. The bond angle is 105 degrees
- Explain why water is a good solvent in living cells.
Water makes an excellent solvent in living cells because of its polarity and the presence of hydrogen bonds that can dissociate many compounds into their respective ions. The hydrous environment in cells makes it suitable for biochemical reactions to occur. Because of its ability to dissolve the majority of substances, water is therefore referred to as the universal solvent; however, this is not wholly true because substances such as lipids are insoluble in water. Water has the ability to form partial electrostatic interaction with solute ions to form a hydrogen shell, unlike other solvent water has a higher ability to dissociate a wide range of solute.
- Life on earth is based on carbon.
- Describe the chemical properties of carbon and explain how they contribute to the size, complexity, and diversity of macromolecules found in living organisms.
- Describe how these properties of carbon are apparent in the structure of DNA.