AP Biology Origins & Molecules of Life Chapter Questions Origins of Life, Large Biological Molecules, Membranes & Enzymes

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1 AP Biology Origins & Molecules of Life Chapter Questions Origins of Life, Large Biological Molecules, Membranes & Enzymes Early Universe 1. Approximately how old is Earth? 2. What one major element was missing from early Earth s atmosphere? 3. How old is the earliest fossil evidence of life on Earth? 4. Explain why a water molecule is polar and describe how water molecules bond together. 5. Summarize Stanley Miller s experiment and its significance. 6. Explain the importance of hydrolysis and dehydration synthesis to the formation of biological molecules. 7. Which biological molecule was the major precursor to life and why? Article Review I The following questions are based on the article DNA Building Blocks found in Meteorites by Brian Vastag 8. Describe the findings of the NASA and Carnegie Institute of Science scientists. 9. How are these findings more significant than those of other meteorites previously studied? 10. Which theory of life would these findings support? The following questions are based on the article It s Alive! It s Alive! Maybe Right Here on Earth by Dennis Overbye What do most scientists agree is essential to describing life? 12. What is the significance of scientific research in producing life from chemicals in a test tube? 13. Describe the significance of Dr. Joyce s test tube results. Are his results most like LUCA or most like a form of life we have not yet discovered, why? 14. Which theory of life would these findings support? The following questions are based on the article Evidence of Earth s Earliest Life based on CalTech News Release and published in the AstroBiology Magazine Describe what stromatolites are and where biological evidence is found. 16. What can the study of stromatolites contribute to our understanding of biology and life on Earth? 17. How can our study of stromatolites on Earth be extended to Mars? Properties of Water 18. List the four properties of water that help support life.

2 19. Distinguish between cohesion and adhesion. Provide real life examples of each. 20. Explain the process and significance of evaporative cooling. 21. Describe the structural difference in water as a solid and a liquid. 22. Explain how water is able to dissolve a solute. 23. Describe the difference between how acids and bases break apart in water. Amino Acids 24. Differentiate between monomers and polymers. 25. Describe the structure of an amino acid and identify the area that makes each of the 20 amino acids unique. 26. Summarize the different levels of protein structure? 27. What is significant about the tertiary structure of a protein? 28. Explain the relationship between protein folding and water. 29. Explain protein denaturation and what causes it. Carbohydrates, Nucleotides, Lipids 30. What three elements are carbohydrates composed of and what are their ratios to one another? 31. Explain the relationship between glucose and polysaccharides. 32. Provide an example of a carbohydrate at each of the three different structural levels. 33. Describe the basic structure of a nucleotide. 34. Summarize the major differences between RNA and DNA. 35. How are lipids unique from the other large biological molecules? 36. Distinguish between saturated and unsaturated lipids. Cycles of Matter 37. How does the law of conservation of matter relate to biology? 38. Summarize the steps of the water cycle. 39. Summarize the carbon cycle. 40. Where and in what form is most carbon found? 41. Where and in what form is nitrogen found? 42. Explain the process and significance of nitrogen fixation. 43. Where is most phosphorous found and what does it provide a building block for? Membranes, Diffusion, Osmosis 44. Describe what is unique about the structure of phospholipids that allows them to form plasma membranes. 45. Describe the importance of cholesterol, glycoproteins, and glycolipids to the formation of the plasma membrane. 46. Describe and distinguish between the two types of passive transport. 47. Create your own example of hypertonic, hypotonic, and isotonic solutions.

3 Facilitated Diffusion, Sodium Potassium Pump 48. Describe the role of transport proteins in passive transport. 49. Distinguish between the movement of water across the membrane via osmosis and through aquaporins. 50. How does active transport differ from passive transport? 51. Summarize the movement of molecules through the sodium-potassium pump. 52. Explain the role of ATP in the sodium-potassium pump. Electrochemical Gradients, Exocytosis, Endocytosis 53. Describe the two parts that comprise an electrochemical gradient. 54. Do most eukaryotic cells maintain a positively or negatively charged interior? 55. Distinguish between exocytosis and endocytosis. 56. Describe the three types of endocytosis. Enzymes, Enzyme Inhibition 57. Identify what enzymes are composed of and describe how they work. 58. Distinguish between competitive inhibition, allosteric competitive inhibition, and non-competitive inhibition. 59. Which type of inhibition can be combated and how? Enzyme Function, Optimal Environments, Feedback Inhibition 60. Identify the factors that can affect enzyme function and describe how the enzyme is affected. 61. How is enzyme function related to protein folding? 62. Describe how cofactors differ from allosteric inhibitors. 63. Using the following feedback inhibition diagram, identify which end product would still be produced if there was an abundance of product 9 and why. The curved arrows represent the feedback pathways. Article Review II The following questions are based on the article The Best Solution to World Thirst May Be Desalination by Robert Gonzalez

4 64. What is desalination and why is it necessary? 65. Describe the old method of desalination and its downfalls. 66. Describe the process we are now using for desalination and how it has evolved to become more efficient. 67. What is the area of research that the authors hope will become a focus and why? The following questions are based on the article Biofuel Enzymes in Hot Water" by Tim Wall Describe the significance of the function of the enzyme that scientists have discovered. 69. Describe how biofuels are made. 70. How can this new microbe change the process of making biofuels?

5 Answers Billion Years Old 2. Oxygen Billion Years Old 4. A water molecule is polar because there is an uneven distribution of charges between the more electronegative oxygen atom and the two hydrogen atoms. Hydrogens on one water molecule are attracted to the oxygen atoms of another molecule, forming intermolecular bonds called hydrogen bonds. 5. Stanley Miller set up an experiment that simulated the conditions of primitive Earth including the atmosphere, water, and lightning. He found that the inorganic molecules that he started with ended up producing the 20 amino acids we currently have on Earth. This showed that inorganic monomers were capable of forming organic monomers under the conditions of primitive Earth. 6. Dehydration synthesis is the process by which monomers form polymers. Hydrolysis provides a mechanism by which polymers can be broken down to form new molecules. 7. RNA because it was able to replicate, metabolize, and catabolize. These are some of the functions that are essential to life today, but have been taken over by other molecules. Questions 8-17 will be answered during class discussion 18. Cohesive behavior, ability to moderate temperature, expansion upon freezing, and versatility as a solvent. 19. Cohesion is the hydrogen bonding of water molecules to other water molecules. Adhesion is the attraction of water molecules to non-water molecules. Cohesion between water molecules occurs in plant stems and also at the surface of a water sample thereby creating surface tension. Adhesion occurs in plants when water molecules are attracted to the plant cell walls and use this attraction to fight the pull of gravity. 20. Evaporative cooling is the process by which water is converted from a liquid to a gas, and as that occurs the liquid left behind is cooled because the heat was transferred between the water molecules to allow some of them to change to gas. This allows bodies of water to maintain a more consistent temperature, thereby supporting the life within the body of water. 21. As a liquid, the hydrogen bonds between water molecules are continuously formed and broken so there is less order and stability to their structure. As a solid, the hydrogen bonds between water molecules are

6 much more stable and are more spread out allowing air to be trapped between the molecules making the solid form less dense than the liquid. 22. The negatively charged side of the water molecules (the oxygen atom) are attracted to the positively charged molecules in the solute, while the positively charged side of the water molecules (the hydrogen atoms) are attracted to the negatively charged molecules in the solute. This attraction allows the water molecules to pull apart the solute molecules. 23. Acids dissociate into hydronium ions and bases separate into hydroxide ions. 24. Monomers are small basic subunits that make up complex polymers. 25. An amino acid is composed of an amine group, a carboxyl group, and a side chain. The side chains are what make each of the 20 amino acids differ from one another. 26. The primary structure is a chain of amino acids, the secondary structure consists of alpha helices and beta pleated sheets, the tertiary structure is the 3D structure created by hydrophobic and hydrophilic reactions between the R- groups, and the quaternary structure consists of more than one polypeptide chain. 27. The tertiary structure is what gives the protein its function. 28. The hydrophobic and hydrophilic properties of the proteins in water cause them to fold in a way that allows the hydrophobic amino acids to be on the inside of the structure away from the water, while the hydrophilic amino acids are on the outside where they can interact with the water. 29. Denaturation of a protein can occur because of a change in temperature, ph, or salinity. When any of these levels change to one that is not optimal for the protein, the protein begins to unfold and because it is the shape of the protein that determines its function, the function is lost. 30. Carbon, hydrogen, and oxygen with a ratio of 1:2:1 31. Glucose molecules are the monomers that form polysaccharides. 32. Monosaccaharide- glucose or fructose, disaccharide- sucrose, polysaccharide- starch, glycogen, cellulose 33. A 5-carbon sugar, a nitrogenous base, and a phosphate group. 34. RNA is composed of ribose, has the base uracil instead of thymine, is single stranded, can take on many shapes, and less stable than DNA. DNA is composed of deoxyribose, has the base thymine instead of uracil, is double stranded, forms a double helix shape only, and is more stable than RNA. 35. They do not form polymers. 36. Saturated lipids are all formed with single bonds, have the maximum number of hydrogen atoms possible and are solid at room temperature.

7 Unsaturated lipids have double bonds and/or triple bons and are liquid at room temperature. 37. The Earth acts as a closed system when it comes to matter and since matter can neither be created nor destroyed, it needs to be continually cycled through the Earth and its organisms. 38. Water from lakes, oceans, etc. is evaporated into the clouds and is absorbed through the soil by plants. Water from plants is transferred to the clouds through transpiration. The water from the clouds is returned to the ground and plants through precipitation Plants utilize carbon from the atmosphere during photosynthesis; carbon from plants is digested by other organisms and released to the atmosphere through cellular respiration. Through burial and decomposition under pressure the carbon from dead organisms is converted to fossil fuels. Mining, burning of forests, burning of fossil fuels, volcanic activity, and erosion release carbon back to the atmosphere and into the ocean. 41. In the atmosphere as carbon dioxide. 42. In the atmosphere as the gas N Nitrogen fixation allows atmospheric nitrogen to be converted to forms that are usable by organisms. Bacteria in the soil convert N2 into ammonium, nitrates, and nitrites, which are used by producers to make proteins. 44. Phosphorous is mostly found on land in rocks, soil, and sediment. It is an essential component of nucleic acids and ATP. 45. Phospholipids are an amphiphilic, so their hydrophobic ends orient themselves on the inside of the plasma membrane bilayer to hide from the water and the hydrophilic ends orient themselves on the outside. 46. Cholesterol is a lipid found only in animal cell membranes that helps provide additional stability for the membrane and makes it less penetrable to water molecules. Glycoproteins have a carbohydrate attached to the proteins in the membrane and serve as points of attachment for other cells. Glycolipids are found on the surface of the membrane and are lipids with a carbohydrate attached. Glycolipids provide energy and aid in cell recognition. 47. Two types of passive transport are osmosis and diffusion; both are responsible for the net movement of molecules down their concentration gradient without the use of energy. Diffusion specifically refers to solute molecules, and osmosis is specific to water molecules. 48. Many acceptable answers. 49. Transport proteins aid in the diffusion of solute and water molecules across the membrane down their concentration gradients by

8 providing specific channels for the molecules to move through so they do not have to move directly through the phospholipids bilayer. 50. The movement of water molecules through osmosis and through aquaporins are both examples of passive transport because they do not require energy. The movement of water molecules through aquaporins is more efficient than the movement through osmosis as a specific channel for the water molecules is provided so they do not have to navigate through the membrane as in osmosis. 51. Active transport requires the use of energy and passive transport does not. 52. Three positively charged sodium ions are moved from the inside of the cell to the outside, and then two positively charged potassium ions are moved from outside the cell to the inside. 53. ATP binds to the channel protein on the inside of the cell, causing the protein to change shape to suit the sodium ions. As the sodium ions are released to the outside of the cell, a phosphate group from the ATP is lost and the now ADP molecule is released from the protein causing it to change shape to accept the potassium ions. The potassium ions are then released to the inside of the cell and the process repeats itself. 54. The difference in charge across the membrane and the difference in ion concentration across the membrane. 55. Negatively 56. Exocytosis moves large molecules from inside the cell to the outside, while endocytosis moves molecules from outside the cell to inside the cell. 57. Phagocytosis is the taking in of solid particles, pinocytosis is the taking in of substances that dissolve in liquids, and receptor-mediated endocytosis is the use of a protein coat and receptor on the membrane to help the vesicle get through. 58. Enzymes are proteins and work by lowering the activation energy of a reaction. 59. Competitive inhibition is when an inhibitor that is similar in shape to the substrate binds at the active site of the enzyme and therefore blocks the substrate from binding. Allosteric inhibition is when the inhibitor binds at an allosteric site, causing the enzyme to change conformation while the inhibitor is bound, thereby not allowing the substrate to bind. Noncompetitive inhibition is when an inhibiter binds at a site separate from the active site causing the active site to change shape, thereby preventing the substrate from binding to the active site. 60. Increasing the substrate level so that there is a greater chance for the substrate to find the enzyme before the inhibitor can combat competitive inhibition.

9 61. Temperature and ph can affect enzyme function by causing the protein to denature and therefore lose its function. 62. The function of the protein is dictated by its shape. 63. Cofactors help substrate bind to the active site by helping the substrate fit into the active site, whereas allosteric inhibitors prevent the substrate from binding to the active site. 64. Product 11 would still be produced because the feedback mechanism from product 9 would stop molecule 3 from continuing to produce product 6, while there is nothing affecting the pathway from 1 to 11. Questions will be answered during in class discussion.