Chat with AIExam 13: How Cells Obtain Energy From Food
You are stranded on an island with no way to communicate or signal for help.Your only hope is that somebody has tracked your last known location and will begin a search from there.Nevertheless, it will be a while before you have a chance of seeing another person.You have found a fresh stream of water at the center of the island, but other than green leafy plants, food options appear nonexistent.
A.What substances are used as energy stores within your body? In which organs?
B.Which will be used first in the absence of ingesting external sources of energy? How long will this source last?
C.What other substance will your body then turn to? On average, how long before you run out of that fuel source? Explain why this second fuel source is a better choice than the first-used source as your long-term energy store.
D.What enzyme is required for the breakdown and usage of the energy source you listed in part B? If you are a person with a deficiency in that enzyme, how does this affect your other estimates?
(36) 
VerifiedA.Glycogen (a polymer of glucose, stored in the liver and skeletal muscle) and triacylglycerol (storage molecule for fatty acids in adipose) are the fuel molecules you have stored.The protein in your skeletal muscle can be broken down as the last fuel option your body has available.
B.Glycogen in the liver will be the first fuel source consumed.This will be burned within the first 12-24 hours.Glycogen stored in your skeletal muscle tissue will be used as the liver glycogen levels go down, as your system attempts to maintain normal blood glucose levels.
C.The triacylglycerol (TAG) molecules in adipose cells will be used as glycogen levels wane.These lipids are cleaved into glycerol and free fatty acids, and the fatty acids are released into the bloodstream for use by the rest of your body.TAG is a better storage molecule because fatty acid metabolism is more efficient (yields more ATP per molecule than glucose) and can be stored in a smaller volume.Glycogen is highly hydrated, and takes up more intracellular space than lipid droplets.Lipid stores could fuel your body as long as one month, depending on the net volume of lipids stored and your level of activity.
D.Glycogen is broken in to glucose subunits by glycogen phosphorylase.A deficiency in this enzyme would mean that your ability to break down glycogen is impaired.In order to supplement the fuel to meet your body's needs, you may burn fatty acids more quickly.You should also expect your glycogen stores to last longer in both the liver and skeletal muscle.
For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below.Not all words or phrases will be used; each word or phrase should be used only once.
Biological systems __________ hydrocarbons in stepwise __________ reactions.Glucose is the preferred energy source in eukaryotes, and must be converted into __________ before it can be transported across the __________ mitochondrial membrane for use in the citric acid cycle.The citric acid cycle is critical for the mitochondrion's subsequent production of __________.
ATP catabolic inner outer permeable acetyl CoA electrons isomerize oxidize protons anabolic glycolysis kinase peptides pyruvate anaerobic GTP
(38) VerifiedBiological systems oxidize hydrocarbons in stepwise catabolic reactions.Glucose is the preferred energy source in eukaryotes, and must be converted into pyruvate before it can be transported across the inner mitochondrial membrane for further oxidation in the citric acid cycle.The citric acid cycle is critical for the mitochondrion's subsequent production of ATP.
In step 7 of the citric acid cycle, fumarase catalyzes the addition of a water molecule to a carbon-carbon double bond (see Panel 13-2).Can this be considered an oxidation reaction? Explain your answer.
(33) VerifiedYes.In the citric acid cycle, the overall process oxidizes carbon molecules to produce carbon dioxide.Although, fumarase does not directly remove electrons from its substrate (as do the enzymes that catalyze steps 3, 4, 6, and 8), the addition of water across the double bond in fumarate leaves one of its carbon atoms in a more oxidized state.This is because one of the carbons becomes bonded to an oxygen atom.In this arrangement, the carbon atom shares its electrons unequally across the new bond (see Figure 3-65).
When glucose is being used up and not replaced from food intake, the blood sugar level can be maintained by synthesizing glucose from smaller molecules such as pyruvate or lactate.This process is called gluconeogenesis.Which organ is principally responsible for supplying glucose to the rest of the body when glucose reserves are low?
(22) Fatty acids can easily be used to generate energy for the cell.Which of the following fatty acids will yield more energy? Explain your answer.
(27) Which of the following steps or processes in aerobic respiration include the production of carbon dioxide?
(43) The intermediates of the citric acid cycle are constantly being depleted because they are used to produce many of the amino acids needed to make proteins.The enzyme pyruvate carboxylase converts pyruvate to oxaloacetate to replenish these intermediates.Bacteria, but not animal cells, have additional enzymes that can carry out the reaction acetyl CoA + isocitrate → oxaloacetate + succinate.Which of the following compounds will NOT support the growth of animal cells when used as the major source of carbon in food, but will support the growth of nonphotosynthetic bacteria?
(38) Which of the following polymers of glucose is used as a vehicle to store energy reserves in animal cells?
(33) Step 3 in glycolysis requires the activity of phosphofructokinase to convert fructose 6-phosphate into fructose 1,6-bisphosphate.Which of the following molecules is an allosteric inhibitor of this enzyme?
(30) Step 6 of the citric acid cycle is catalyzed by succinate dehydrogenase.Keeping in mind that dehydrogenases catalyze redox reactions, which are the products of the reaction in which succinate is oxidized?
A)fumarate, NADH
B)fumarate, FADH2
C)fumarate, FADH2
D)succinyl CoA, NADH
(40) For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below.Not all words or phrases will be used; each word or phrase should be used only once.
amino acids galactose nucleotides carbon fixation glucose oxidative phosphorylation citric acid cycle glycogen pyruvate fatty acid insulin starch fermentation lactate triacylglycerol
A carbon atom in a CO2 molecule in the atmosphere eventually becomes a part of one of the enzymes that catalyzes glycolysis in one of your cells.The CO2 first enters a cell in a corn leaf, where photosynthesis fixes the carbon to make it part of a sugar molecule; this travels from the leaf to an ear of corn, where it is stored as part of a polysaccharide __________ molecule in the corn seed.You then eat a corn chip made from the corn seed.You digest the corn seed, and the free __________ travels in your bloodstream, eventually being taken up by a liver cell and stored as __________.When required, this storage molecule breaks down into glucose 1-phosphate, which enters the glycolytic pathway.Glycolysis produces __________, which is converted into acetyl CoA, which enters the __________.Several intermediates in this process can provide the carbon skeleton for the production of __________, which are then incorporated into the enzymes that catalyze steps in glycolysis.
(37) What purpose does the phosphorylation of glucose to glucose 6-phosphate by the enzyme hexokinase serve as the first step in glycolysis?
(29) The conversion of fructose 1,6-bisphosphate to fructose 6-phosphate is catalyzed by a fructose 1,6-bisphosphatase and is one of the final steps in gluconeogenesis.Which of the following molecules is an allosteric activator of this enzyme?
(34) Which of the following descriptions best matches the function of a dehydrogenase?
(31) Verified (34) The conversion of glyceraldehyde 3-phosphate to 1,3 bisphosphoglycerate in step 6 of glycolysis generates a "high-energy" phosphoanhydride bond.Which of the following BEST describes what happens to that bond in step 7?
(33) In humans, glycogen is a more useful food-storage molecule than fat because
(33) The oxygen-dependent reactions required for cellular respiration were originally thought to occur in a linear pathway.By using a competitive inhibitor for one enzyme in the pathway, investigators discovered that these reactions occur in a cycle.Which enzyme was inhibited?
(36) Select the best option to fill in the blanks of the following statement: Fermentation is a/an __________ process that converts __________into carbon dioxide and __________.
(40) Which of the following stages in the breakdown of the piece of toast you had for breakfast generates the most ATP?
(34) 
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