Thursday
November 27, 2014

Homework Help: chemistry

Posted by cassie on Wednesday, February 10, 2010 at 10:19am.

1. The atomic number of carbon is 6. Its nucleus must contain:
a) 6 neutrons and 6 protons.
b) 3 protons and 3 neutrons.
c) 6 neutrons and no electrons.
d) 6 protons and no electrons.
e) 6 protons and 6 electrons.



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2. The second orbital shell of an atom can hold ___ electrons.
a) 2
b) 3
c) 4
d) 6
e) 8



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3. A covalent bond is formed when:
a) two non-polar molecules associate with each other in a polar environment.
b) a positively charged particle is attracted to a negatively charged particle.
c) one atom gives up electrons to another atom.
d) two atoms share electrons.
e) two polar molecules associate with each other in a non-polar environment.



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4. When you put a piece of chocolate on your tongue, your brain registers a sensation of sweetness. What aspect of molecules is responsible for their having a particular taste?
a) the total number of protons in the molecule
b) the number of hydrogen bonds in the molecule
c) the total number of electron shells in the atoms of the molecule
d) the ratio of covalent bonds to ionic bonds joining the atoms of the molecule
e) the molecule's shape



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5. Which of the following phenomena is most likely due to the high cohesiveness of water?
a) Lakes and rivers freeze from the top down, not the bottom up.
b) The "Jesus lizard" can run across the surface of liquid water for short distances.
c) Adding salt to snow makes it melt.
d) The temperature of Santa Monica Bay, off the coast of Los Angeles, fluctuates less than the air temperature throughout the year.
e) All of the above are due to the cohesiveness of water.



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6. Water can absorb and store a large amount of heat while increasing only a few degrees in temperature. Why?
a) The heat must first be used to break the hydrogen bonds rather than raise the temperature.
b) The heat must first be used to break the ionic bonds rather than raise the temperature.
c) The heat must first be used to break the covalent bonds rather than raise the temperature.
d) An increase in temperature causes an increase in adhesion of the water.
e) An increase in temperature causes an increase in cohesion of the water.



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7. A chemical compound that releases H+ into a solution is called:
a) a proton.
b) a base.
c) an acid.
d) a hydroxide ion
e) a hydrogen ion



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8. Which of the following foods is not a significant source of complex carbohydrates?
a) fresh fruit
b) rice
c) pasta
d) oatmeal
e) All of the above are significant sources of complex carbohydrates.



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9. Sucrose (table sugar) and lactose (the sugar found in milk) are examples of:
a) naturally occurring enzymes.
b) simple sugars.
c) monosaccharides.
d) disaccharides.
e) polyunsaccharide sugars.



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10. Which of the following statements about starch is incorrect?
a) Starch is the primary form of energy storage in plants.
b) Starch consists of a hundred or more glucose molecules joined together in a line.
c) Starch tastes sweet because it is made from glucose.
d) Starch is a polysaccharide.
e) All of the above statements about starch are correct.



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11. Which of the following statements about fiber is incorrect?
a) Dietary fiber reduces the risk of colon cancer.
b) Fiber in the diet slows the passage of food through the intestines.
c) Humans are unable to extract any caloric value from fiber.
d) The cellulose of celery stalks and lettuce leaves is fiber.
e) Fiber passing through the digestive system scrapes the wall of the digestive tract, stimulating mucus secretion and aiding in the digestion of other molecules.



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12. In an unusually detailed dissection of your dinner, you isolate an unknown fatty acid. It is a liquid at room temperature (that is, has a low melting point) and contains carbon-carbon double bonds. What are you most likely to be eating?
a) a plant
b) a cow
c) a pig
d) chicken
e) lamb



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13. An unsaturated fatty acid is one in which:
a) carbon-carbon double bonds are present in the hydrocarbon chain.
b) the hydrocarbon chain has an odd number of carbons.
c) the hydrocarbon chain has an even number of carbons.
d) no carbon-carbon double bonds are present in the hydrocarbon chain.
e) not all of the carbons in the hydrocarbon chain are bonded to hydrogen atoms.



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14. Which statement about phospholipids is incorrect?
a) Because their phosphate groups repel each other, they are used as organisms chief form of short-term energy.
b) They are hydrophobic at one end.
c) They are hydrophilic at one end.
d) They are a major constituent of cell membranes.
e) They contain glycerol linked to fatty acids.



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15. Proteins are an essential component of a healthy diet for humans (and other animals). Their most common purpose is to serve as:
a) raw material for growth.
b) fuel for running the body.
c) organic precursors for enzyme construction.
d) long-term energy storage.
e) inorganic precursors for enzyme construction.



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16. Dietary proteins:
a) are considered "complete" only if they contain the eight essential amino acids required by humans.
b) consist of all 20 amino acids required in the human body.
c) are considered "complete" only if they contain the 12 non-essential amino acids required by humans.
d) are nutritionally identical, since all are broken down into their constituent amino acids in the digestive system.
e) can be obtained from animal sources but not plant sources.



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17. The primary structure of proteins is often described as amino acids connected like beads on a string. In this same vein, which of the following images best describes a proteins quaternary structure?
a) threads in a cloth
b) needles in a haystack
c) rungs on a ladder
d) links on a chain
e) coils in a spring



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18. Which of the following statements about enzymes is incorrect?
a) Enzymes can initiate chemical reactions.
b) Enzymes speed up chemical reactions.
c) Enzymes often induce conformational changes in the substrates that they bind.
d) Enzymes contain an active site for binding of particular substrates.
e) Enzymes undergo a permanent change during the reactions they promote.



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19. Which of the following nucleotide bases are present in equal amounts in DNA?
a) adenine and cytosine
b) thymine and guanine
c) adenine and guanine
d) thymine and cytosine
e) adenine and thymine



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20. Which type of macromolecule contains an organism's genetic information?
a) polysaccharide
b) monosaccharide
c) fatty acid
d) DNA
e) phospholipid



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21. All of the following are features of RNA except:
a) a sugar-phosphate-sugar-phosphate backbone.
b) a coiled double-stranded structure.
c) a different type of sugar than is found in DNA.
d) an ability to direct protein production.
e) a different type of base than is found in DNA.

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