Name: __________________________________________ Unit 1: Chemistry of Life TEST Unit 1: Chemistry of Life Part 1: Multiple Choice: (2 pts each) _____1. Which of these is the best explanation for why the meniscus of water in the capillary tube to the right is concave? a. The adhesive forces are stronger than the cohesive forces. b. The cohesive forces are stronger than the adhesive forces. c. The surface tension of the water is causing water molecules to be drawn downward. d. Water has formed polar covalent bonds with the capillary tube walls causing the water to be more attracted to the walls of the capillary tube than with other water molecules. _____2. Which of the following functional groups will you always find in an amino acid? a. -OH b. -NH2 c. -C=O d. -CH3 _____3. The image to the right represents a polynucleotide. Which statement below best identifies the polynucleotide with a justification based upon evidence from the image? a. The image represents DNA because it contains the base thymine. b. The image represents DNA because the sugar is deoxyribose. c. The image represents RNA because it is a single strand. d. The image represents RNA because the sugar is ribose. _____4. Nebulin is an actin-binding protein that can be found in skeletal muscles. Nebulin is large in size and functions to stabilize actin and regulate muscle contractions. The gene that codes for nebulin, NEB, is on chromosome 2 in humans. Mutations to the NEB gene can result in mutations in the amino acid sequence of the resulting nebulin protein. If the mutation in the gene causes an amino acid deletion in the sequence of amino acids that make up nebulin, how will this affect the structure of nebulin? a. Only the primary structure of Nebulin will be affected; the secondary and tertiary structures will not be affected. b. Both the primary structure and secondary structure of nebulin will be affected, while the tertiary form will not be affected. c. The primary, secondary, and tertiary structures of nebulin will be affected. d. An amino acid deletion would not affect the structure of nebulin. _____5. You are given a protein with the following amino acid sequence: methionine (nonpolar)-glycine (nonpolar)-serine (polar)-alanine (nonpolar)-lysine (polar) If an amino acid substitution occurred in this polypeptide chain, predict which option would have the most significant impact on the structure and function of the protein. a. Serine is replaced by lysine (polar). b. Glycine is replaced by alanine (nonpolar). c. Alanine is replaced by leucine (nonpolar). d. Lysine is replaced by tryptophan (nonpolar). © Getting Down With Science 2020 _____6. The structure of cysteine, an amino acid, can be seen to the right. Cysteine is one of only a few amino acids that contains sulfur. In which structural level of a protein would cysteine play the most significant role? a. Primary structure b. Secondary structure c. Tertiary structure d. None of the above, it would play an equal role at all structural levels _____7. You are given the following strand of DNA 5’-ATACGTA- 3.’ What would the complementary strand of DNA be? a. 3’-TATGCAT- 5’ b. 5’-UAUGCAU- 3’ c. 5’-TATGCAT- 3’ d. 3’-UAUGCAU- 5’ _____8. The image to the right represents two fatty acid chains found in phospholipids. Which fatty acid chain would most likely be found in the plasma membrane of an aquatic organism that lives in cold waters? a. Fatty acid chain A because it is unsaturated, which allows for more flexibility in the membrane at cold temperatures. b. Fatty acid chain B because it is saturated, which allows for more flexibility in the membrane at cold temperatures. c. Fatty acid chain A because it is saturated, which allows for more flexibility in the membrane at cold temperatures. d. Fatty acid chain B because it is unsaturated, which allows for more flexibility in the membrane at cold temperatures. _____9. Phosphorus is an important element in building both... a. Proteins and lipids b. Nucleic acids and lipids c. Proteins and nucleic acids d. Carbohydrates and proteins _____10. Glucose serves as nutrients and fuel for cells. In which process is glucose used? a. Photosynthesis b. The electron transport chain c. Cellular respiration d. Photorespiration _____11. An ionic bond occurs... a. When there is a transfer of electrons from one atom to another b. When two or more atoms share electrons c. Between two nonmetals d. Between two metals _____12. Which of the following is the best explanation for why ice is less dense than liquid water? a. The partial charges of water repel molecules from each other, which creates space between molecules, thus resulting in ice being less dense than water. b. When ice begins to form it takes on a crystalline structure due to the bonding between water. This crystalline structure allows for ice to be denser than water, which allows it to float. c. Water has a high surface tension, which keeps the ice on the surface of the water. d. Hydrogen bonds stabilize the structure of water keeping molecules separate from each, thus resulting in ice being less dense than water. © Getting Down With Science 2020 Use the following passage to answer questions 13-17. The most common cause of death worldwide is cardiovascular disease. One indicator, or risk factor, for cardiovascular disease is having low-density lipoprotein cholesterol (LDL-C), also known as the “bad cholesterol,” in the blood. While there are many treatments that can lower LDL-C levels, a large percentage of the population is not able to tolerate the drugs prescribed by their physicians. Researchers have recently found a potential cause for high LDL-C levels in some people; there is a gene in the DNA of liver cells, PCSK9, that seems to prevent receptors in the body that uptake LDL-C from functioning properly. Further evidence supporting this comes from data gathered from people with mutations in their PCSK9 gene that subsequently have low LDL-C levels. To research this observation scientists injected mice with a virus that would attack the PCSK9 gene, thus causing it to lose function. The LDL-C levels in the mice were then analyzed over the course of 96 hours. _____13. What is the independent variable? a. The LDL-C levels b. The PCSK9 g ene c. The virus d. The receptors that uptake LDL-C _____14. What is the dependent variable? a. LDL-C levels b. The PCSK9 g ene c. The virus d. The receptors that uptake LDL-C _____15. Which of the following best represents a potential hypothesis that the researchers were testing? a. Mice injected with the virus that will attack the PCSK9 g ene will have reduced levels of low-density lipoprotein cholesterol in their blood because the gene will lose function and therefore will not affect the receptors that uptake LDL-C. b. Mice injected with the virus that will attack the PCSK9 g ene will have increased levels of low-density lipoprotein cholesterol in their blood because the gene will lose function and therefore will not affect the receptors that uptake LDL-C. c. Mice injected with the virus that will attack the PCSK9 g ene will have reduced levels of low-density lipoprotein cholesterol in their blood because the gene will lose function and therefore will affect the receptors that uptake LDL-C. d. Mice injected with the virus that will attack the PCSK9 g ene will have increased levels of low-density lipoprotein cholesterol in their blood because the gene will lose function and therefore will affect the receptors that uptake LDL-C. _____16. If the null hypothesis was supported, what results would the researchers expect to see? a. The LDL-C levels in the blood of mice treated with the virus would increase in comparison to mice not treated with the virus. b. The LDL-C levels in the blood of mice treated with the virus would decrease in comparison to mice not treated with the virus. c. The LDL-C levels in the blood of mice treated with the virus would be the same or similar to mice not treated with the virus. d. None of the above. _____17. Which of the following represents a suitable positive control for the experiment? a. Mice exposed to no treatment. b. Mice exposed to a treatment known to reduce LDL-C levels. c. Mice exposed to the virus. d. None of the above. © Getting Down With Science 2020 Part 2: Macromolecule Identification: Label the descriptions below with the correct macromolecule. Macromolecules may be used more than once or not at all. (2 pts each) _____18. Stores hereditary information A. Carbohydrates _____19. Comprises a major portion of the plasma membrane B. Proteins _____20. Plants use this macromolecule for storage C. Lipids _____21. Function as antibodies to help protect the body from disease D. Nucleic acids _____22. Monomers are bonded through phosphodiester linkages _____23. Includes steroids _____24. Monomers come together through the formation of peptide bonds Part 3: Short Responses and Calculations: Answer each question in the space provided. 25. Complete the chart below by filling in the missing sections. (8 pts) Macromolecule Monomer Polymer Carbohydrates Proteins Lipids Nucleic acids 26. The image below represents glucose and fructose. Diagram the reaction that would take place between these two carbohydrates to form sucrose. In the space to the right, identify and describe the reaction. (4 pts) © Getting Down With Science 2020 27. Identify and describe each level of protein structure and how it contributes to the overall structure/function of a protein. Be specific in your descriptions making sure to only highlight the key details. (8pts) 28. Describe standard deviation and discuss what it means if data has a low standard deviation versus a high standard deviation. (3 pts) 29. Using the data table to the right, calculate the mean, median, and mode of the data. Add your final calculations to the table and show your work in the space below. (4 pts) 30. Using the data table to the right, calculate the mean, standard deviation, and standard error of the data. Add your final calculations to the table and show your work in the space below. (4 pts) © Getting Down With Science 2020 Read the passage below to answer questions 31-36. The two bacteria most commonly responsible for dental cavities are Streptococcus mutans and Lactobacillus. If left untreated these bacteria can lead to tooth pain, infection, and tooth loss. Both bacteria produce acid in the presence of sugar. Since teeth are composed of minerals, teeth are very sensitive to changes in pH. Low pH around the teeth can lead directly to the loss of enamel and the formation of cavities. In order to determine the effectiveness of a new toothpaste, researchers expose patients to sugar and measure the change in pH on their upper molars before and after consumption of the sugar. One set of patients is then asked to brush their teeth for two minutes, while another set of patients is asked to only rinse their mouths with water. A third set of patients is only asked to rinse with fluoride, a chemical compound known to kill bacteria on and around teeth. The pH of the upper molars for all three sets of patients was then recorded. The data can be seen in the chart below. Mean pH on Upper Molars ( ± 2 SEẊ) Treatment Group Mean pH Before Sugar Mean pH After Sugar Mean pH After Treatment Brushing with New Toothpaste 7.5 ± 0.1 6.3 ± 0.2 7.4 ± 0.1 Rinsing with Water 7.4 ± 0.2 6.5 ± 0.2 6.6 ± 0.2 Rinsing with Fluoride 7.5 ± 0.1 6.4 ± 0.1 7.5 ± 0.2 31. Identify the independent variable and the dependent variable. List 3 aspects of the experiment that the researchers should keep constant between all treatment groups. (5 pts) 32. State the null and one possible alternative hypothesis for the experiment. (2 pts) 33. What was the purpose of the treatment group that only rinsed with water? (2 pts) © Getting Down With Science 2020 34. Using the space provided, construct an appropriately labeled graph to represent the mean pH of molars after sugar and the mean pH of molars after treatment for each treatment group. Make sure to include error bars. (8pts) 35. What conclusion(s) can the researchers draw from this data? (2 pts) 36. The new toothpaste being tested works by changing the chemical environment of the mouth. Describe how this would affect proteins produced by Streptococcus mutans and Lactobacillus? (2 pts) © Getting Down With Science 2020 © Getting Down With Science 2020
