L112 – Exam One – Su’14 Answer Key Short answers: 40pts 1. List four properties of life (characteristic of all living organisms). (2pts) Explanations were not expected (only need four). 1. cellular organization • are made up of one or more cells 2. metabolism • use energy (transfer of energy from one form to another) 3. homeostasis • ability to maintain relatively stable internal environment 4. growth & reproduction • all living thing grow & reproduce (asexually or sexually) 5. respond to stimuli • ability to respond to external stimuli (light, food) 6. heredity • all organisms posses a genetic system – DNA 7. capacity to adapt • all organisms posses adaptations which allow them to survive and reproduce in their environments • populations of organisms can adapt to changing environmental condition 2. Diagram both a chlorine atom (atomic #17) and a fluorine atom (atomic #9) using the “mini solar system” method (don’t need the protons and neutrons). Would you expect these two elements to react similarly in chemical reactions? Why? (3pts) Yes, would except them to behave similarly due to having the same # of electrons in their valence shell (7). 3. The molecular formula for Urea is CO(NH2)2. The mass of a carbon atom is 12, an oxygen atom is 16, a nitrogen atom is 14 and a hydrogen atom’s mass is one. How many grams of urea do you need to make a 1M solution? Show your work. (2pts) molecular mass – (1*12) + (1*16) + (2*14) + (4*1) = 60 60g/1L of water = 1M Urea solution 4. What is pH? Are high or low pH values acidic? What is the pH of distilled water? (2pts) pH is a measure of H+ concentration low pH is acidic – has a high H+concentration high pH is basic – has a low H+ concentration pH of distilled water is neutral (7.0). 5. Diagram a fat molecule emulsified in bile salts. Label (fat and bile salt) & briefly explain the diagram. (Hint: think about a micelle). (2pts) bile salts are amphiphatic – they have a hydrophilic and hydrophobic side hydrophobic side faces the hydrophobic fat, while the hydrophilic side faces the aqueous fluid 6. One property of water is that it acts as a versatile solvent. Diagram a few water molecules dissolving the ammonia molecule depicted below into solution. (Keep in mind that ammonia is a polar organic molecule, not broken down but dissolved into solution). Draw & label the bonds within the water molecule and between water, as well as show the relationship between the water and the solute in terms of bonds that form. (3pts) 7. Draw two 5-‐carbon hydrocarbon chains, one that is branched and another one that is un-‐ branched. (2pts) 8. Indicate the class of macromolecules (e.g., protein) depicted below. (2pts) 9. In the molecules above circle and label the following functional groups (only need to circle one of each; but make sure it is clear what you are circling (2.5pts) a. hydroxyl b. carbonyl c. carboxyl d. phosphate e. amino 10. Draw the concentration gradient of a solute (S) on two sides of a membrane (one side is hypertonic to the other). Draw enough water molecules (just use H2O as the symbol or W – don’t worry about showing the specific bonding just the relationship in space to each other) to show the difference between the concentration of free water molecules and non-‐ free water molecules on the two sides of the membrane. Finally, indicate with an arrow the direction water will move. (3pts) 11. Matching the following cell structures with the appropriate function. (2.5 pts) A. Mitochondrion __I____ cell support /outside of plasma membrane B. Central vacuole __H___ modification, sorting & secretion of lipids and proteins C. Chloroplast ___A___ site of cellular respiration (ATP synthesis) D. Plasma membrane ___C___ site of photosynthesis E. Nucleus __D___ movement of substances into and out of cell F. Cytosol __B___ storage of water & regulation of cell volume in a plant cell G. Lysosome __E___ houses genetic material H. Golgi apparatus __F____ fluid environment inside the plasma membrane and outside organelles I. Cell wall __G_____ degradation of (destroys) macromolecules J. Ribosome __J____ site of polypeptide synthesis 12. Indicate with an “X” the area(s) where digestion of the different molecules takes place. (4.5pts) Carbohydrate Protein Digestion Lipid Digestion digestion Oral Cavity X Stomach X Small Intestine X X X 13. Match the following enzymes with the appropriate function (each letter used once): (1.5pts) A. Amylase ______D_____ enzyme that breaks down fat B. Trypsin & Chymotrypsin _____A_____ enzyme that breaks down carbohydrates C. Pepsin _____B, C, E_____ enzyme that breaks down protein D. Lipase ______F_____ enzyme that breaks down nucleic acids E. Peptidase F. Nucleotidases 14. Label the following parts of the nephron (either put the label in the square or number your answers off to the side). 2.5pts #1 – proximal convoluted tubule #2 – decending limb of loop of Henle #3 – thin segment of ascending limb of loop of Henle #4 – thick segment of ascending limb of loop of Henle #5 – distal convoluted tubule #6 – collecting duct 15. For each of the above locations along the nephron, indicate whether water is moving in or out of the tubule lumen, and whether or not Na+ is moving in or out. (2.5pts) #1 – water and Na+ out #2 – permeable to water (moving out) , Na+ not moving #3 – permeable to Na+ (moving out), water not moving #4 – permeable to Na+ (active transport out), water not moving (don’t need active transport) #5 - permeable to water (moving out) and Na+ (moves out – actively pumped)-- though regulated #6 - permeable to water (moving out/in – regulated) not Na+ 16. Explain how the interstitial fluid within the medulla maintains a higher osmolarity than the first part of the loop of Henle. What are the three major factors that contribute to this osmolarity? (3pts) 1. thin segment of ascending loop is permeable to solutes, but not water, which diffuses into interstitial fluid increasing the osmolarity 2. thick segment actively pumps solutes out , but is not permeable to water 3. urea defuses out of the collecting duct, increasing the osmolarity in the interstitial fluid Bonus: 17. Glucose is transported into cells by facilitated diffusion. Researchers studied the rate of uptake by incubating red blood cells in a radioactive glucose solution for two groups of cells. One group of cells was taken from 15-‐day old guinea pigs and another group of cells was taken from 1-‐day old guinea pigs. (a) Using the data that is depicted in the graph below, explain the results of the experiment. (1pt) (b) Develop of hypothesis to explain the difference between the uptake in red blood cells from 15-‐day-‐old and 1-‐month old guinea pigs. (Think about how glucose gets into cells). (1pt) The hardcopy of the exams did not show the colored label some they may mix up which group was which (and that is fine as long as it make sense with the graph). (a) More glucose was taken up more in 15-‐day old guinea pigs, as compared to 1-‐month old guinea pigs. (b) Example hypothesis: As the guineas got older the lost some of the transport proteins that are used to move glucose across the cell membrane. 18. Match the following vitamins and minerals with their appropriate function: (1.5pts) A. Vitamin B2 (riboflavin) ___C____ Component of visual pigments B. Vitamin B9 (folic acid) ___D____ Used in collagen synthesis / antioxidant C. Vitamin A (retinol) ___E____ Aids in absorption & use of calcium D. Vitamin C ___A____ component of coenzyme FAD E. Vitamin D ___F____ Antioxidant; helps prevent damage to cell membranes F. Vitamin E ___B____ Coenzyme in nucleic acid and amino acid metabolism 19. Genetically modified “Orange sweet potato” grown in Africa has had positive health benefits to the local people. Why? What is special about these potatoes? (2pts) Genetically engineered to contain Vitamin A, which is lacking in the diet of many local people dependent on the normal ‘white’ potato. Provided needed nutrient lacking from the diet. -‐-‐ key is the “vitamin A”
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