Margie L. Stinson "Basic Chemistry of Life" Sample Exam Questions 1. The _______________ is located at the center of an atom. It contains the atom's protons and its _________________, which have no electro- magnetic charge. Electrons encircle the nucleus traveling in orbits within energy shells. The protons of the nucleus have a _____________ electromagnetic charge, while the electrons have a _____________ electromagnetic charge. To give you a concept of relative size of these subatomic structures, imagine if the atom were the size of a football stadium, the _____________ at its center would be about the size of a gumball (chewing gum), while the _____________s would be specks of dust orbiting in different energy spheres, with the furthest orbit traveling the outer rim of the stadium. 2. The electromagnetic charge of the ______________ s and the ____________s of an atom are equivalent to its yin and yang. The ____________s located in the nucleus of the atom lack any electromagnetic charge. 3. For our purposes, we can say that the ______________s of an atom have almost no weight, because they are so tiny. The _______________s and the _______________s weigh the same as each other. The atomic weight of the atom is the combined weights of its _____________s and _______________s. 4. Carbon 12 has ___________ protons and _________ neutrons. What is the atomic weight of carbon 12? _________ 5. What would happen if the number of protons of an atom changed? 6. All atoms of a particular element have the same number of ____________s. 7. Hydrogen has ____________ proton(s), __________ neutrons, __________ electrons. The atomic weight of hydrogen is ______________. Why does hydrogen so readily bond with other hydrogen atoms and also with atoms of other elements? Are these bonds considered strong and difficult to break, or are they weak and easily broken? 2 8. Some elements form isotopes so that even though their proton number never changes, their neutron number does change, and thus alters their atomic An example of an element that exists also as isotopes is _______________. When an isotope of an element breaks down (this is occurs as radioactive elements degrade) the isotope does not revert back to the original element, but becomes a new element with the "isotope" number of neutrons. An example is Carbon 14, which reverts- -not back to carbon 12 (with 6 protons and 6 neutrons) but rather to N 14 with 7 protons and 7 neutrons. 9. Atomic energy is __________magnetic energy. It is the balance between the + charge of the ________________s in the center of the nucleus of the atom, and the - charged _____________s orbiting the nucleus in energy shells or spheres. 10. Electrons store energy. Those with the least amount of stored energy orbit the nucleus in energy shells _________________ [closest to / furthest from] the atom's nucleus. Each electron has the potential to do _____________. Thus, this is called potential _________________. 11. The energy sphere closest to the nucleus is labeled the "K" shell. Within this energy shell there is one spherical pathway or orbit in which ________ electrons can travel. This K shell is closest to the nucleus and thus requires the least amount of energy to hold electrons in its orbit. The L energy shell is located further away from the nucleus, and thus it requires more energy to hold its electrons in orbits. The L shell has four travel pathways or orbits, one spherical in shape, and three that are shaped like a dumbbell weight. __________ (#) electrons can travel in each of these orbits. Consequently, ________ (#) electrons can exist in the L energy shell. The M shell is even further from the nucleus. For this reason, it takes the greatest amount of energy to hold its electrons in orbits at that distance. Similar to the L shell, the M shell contains ______ orbits in which electrons can travel. One of these orbitals is spherical in shape, the other three are shaped similar to a dumbbell weight. __________ electrons can travel in each of these orbitals within the M energy shell. 12. The K energy shell is filled with ________ electrons. The L energy shell is filled with ________ electrons. The M energy shell is similarly filled __________ electrons. The magic "octet" rule refers to what? 13. When an electron goes from one energy shell to another (meaning it changes the distance it is traveling around the nucleus) it either absorbs energy (if it is moving to an orbit further from the nucleus), or it releases energy if it is moving to an orbit ____________ to the nucleus. In the chemical reaction known as photosynthesis, the chlorophyll molecule within cells of a leaf, absorbs energy from the sun. This energy is passed along a series (chain) of protein molecules called “cytochromes”. In essence, they are harnessing solar energy 3 and transforming it into electromagnetic (atomic) energy that will allow molecules of carbon dioxide and hydrogen (from H2O or H2S) to come close enough together that the molecules undergo a chemical reaction and become some form of sugar (such as glucose C6H12O6). During this chemical reaction, their electrons move to outer energy shells (higher energy), and then as they use up that solar energy, their electrons move back to orbits closer to their nuclear centers. As the electrons move closer to the nucleus, energy is released. So, photosynthesis absorbs solar energy allowing the H electrons to absorb energy, and as that solar power is used up the H electrons move back into lower energy levels releasing this energy now as chemical or electromagnetic energy that can be used by the plant for metabolism. This is the base of the food chain. It is what allows all of us consumers to exist. 14. While only _____ (#) electrons can occupy any orbit within an energy shell at any one Time, electrons can move from orbit to orbit. 15. In any case, it is what is happening in the outer energy shell that we are concerned with. If that outer shell is full the atom is stable. If that outer energy shell is not full it can share its electrons with another atom of the same or different element. This type of sharing of electrons is called _____________ bonding. If the atom gives its electrons away or rips electrons from another atom to fill its outer energy shell, this is called ______________ bonding. Does ionic bonding help the atom that is losing or giving away its electrons? Explain. 16. When a metal is reduced of its electrons, it is said to have been ____________ because most often it is oxygen that is doing the reducing. The oxygen atom needs 2 electrons to complete its outer energy shell. Consequently, when it is in the presence of metals (as it frequently is) it takes two electrons from the outer shell of the metal, thus reducing the metal of its electrons. This type of reaction is called an ________________ - _______________ reaction. In this type of reaction, oxygen acts as the _____________________. It _______________ the metal of its electron load. The oxygen atom now has more electrons than it has _____________s, so it now carries a _________________ electromagnetic charge It now is called an ion. The metal atom now has fewer electrons, than it does ______________ and so carries a ___ electromagnetic charge. It is called a + ion. 17. Why is water a solvent? Give an example of a chemical reaction in which water acts as a solvent and explain what is occurring. 18. Explain how water can be ionized. What two molecules or atoms are produced when a water molecule is ionized? How does this relate to the pH of solutions? Which portion of ionized water causes solutions to be acidic? Which portion of ionized water causes solutions to be basic? 4 19. Why is the temperature of water as a liquid more stable than the liquid state of other elements or compounds? What is the biological relevance or significance of the great stability of liquid water? 20. While it requires only one calorie of heat energy to change liquid water one degree centigrade or celsius, it takes 80 calories of energy for water to change from its liquid to solid state, and it takes 540 calories for liquid water to change into a vapor state. This accounts for the great amount of heat needed for evaporation to occur in plants and animals. Water is unique that it is the only common molecule that at temperatures and pressures typical of earth's environment, can be found in three states: as a liquid, as a ___________, and as _____________. 21. Why does ice float on top of liquid water? 22. Now think about life in polar regions. Below the ice there is liquid ocean. Which is more saline, the ice or the water below the ice? 23. If you were to fill a glass full with hot water and then immediately place it in a freezer, when the water freezes, what will happen to the volume of the water? [ Would the glass overflow, or would there now be space that you could pour more water into the glass atop the frozen ice?] Explain what happened to the crystalline structure of the molecules in the water as they cooled and then became frozen. 24. Why do carbons bond so easily with each other? 25. Why does carbon bond easily with hydrogen? 26. Where do we get the water to bathe our biomolecules or to separate into the H and the OH that then bond covalently to our carbon atoms to form the basic structure of our biomolecules? How important is carbon, and carbon-hydrogen molecules to the molecular structure of our cells? 27. Where do we get the carbon that forms the backbone of our biomolecules? 28. Biomolecules are composed primarily of two elements that form chains or rings that are in essence the "vertebral column" or "backbone" of the polymer. These two main elements are: ________________ and ________________. Attached to these chains or rings will be a molecule consisting of a different element or a different molecule composed of several elements. This unique molecule is called the functional group of an organic molecule and is responsible for controlling how that molecule functions or interacts with other molecules. 5 29. ___________________________ is the chemical process that causes monomers to attach to each other forming more complex molecules known as polymers. During this process a molecule of _____________ is released (drops out) and is available for the cell to use for other reactions, such as metabolism. Why does this process only occur in polar situations? During this process energy is stored in carbon: carbon bonds, which bond the monomers together. Specific ___________________ must be present for each chemical reaction to occur. When polymers are split into monomers, energy is released and is available for other chemical reactions to use. Thousands, if not millions, of chemical reactions are occurring simultaneously within the cells of our body. Some reactions absorb energy and store it for other reactions that require energy. 30. Hydrolysis is the process that splits polymers into simpler ___________________. This process requires a water molecule. What is the function of this water molecule? 31. Contrast condensation and hydrolysis of molecules. 32. Explain the process of condensation. 33. Explain the process of hydrolysis. 34. How do enzymes function in forming or breaking apart biomolecules? 35. List different ways that the molecular structure of a biomolecule can differ resulting in molecules that have very different functions. 36. The functional group of an organic molecule determines how the organic molecule ______________________. The functional group always bonds with a carbon of the basic organic molecule. 37. If the functional group is polar, it is: ____ a. hydrophilic and is attracted to a water molecule. b. hydrophobic and is repelled by water molecules. c. hydrophilic and is repelled by a water molecule. d. hydrophobic and is attracted to a water molecule. 38. Why is water a polar molecule? Which part of it is positive, which part is negative? Do like charges attract or repel one another? What is meant by a hydrophobic molecule? What is meant by a hydrophilic molecule? 6 39. By adding an hydroxyl (OH) group to a sugar, a/an _______________ is formed. a. protein b. salt c. alcohol d. nucleic acid 40. What is the functional group of phospholipids? _____________________ 41. Define what is meant by an "isomer" and give an example of a sugar molecule that has two isomers. 42. How do two isomers differ from each other? 43. Do they differ in their molecular formula or in their molecular structure? 44. What are ways in which two molecules can have the same molecular formula but have very different structure and function?
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