Topic: Short course to help understand how we get energy
Marnie
Frequent Contributor (5K+ posts)
Member # 773
posted
The following are the answers to questions posed in the web link:
1. To produce a molecule of adenosine triphosphate (ATP), a cell needs adenosine diphosphate (ADP), phosphate, *an energy source*, and the appropriate enzyme (my note here...CoQ10 to add hydrogen (energy source) and cAMP to remove??? ATP + cAMP -> ADP + energy???)
2. Adenosine diphosphate and adenosine triphosphate differ in the number of phosphate groups they possess; the ``di'' in diphosphate indicates that adenosine diphosphate contains
two phosphate groups,
while the ``tri'' in triphosphate tells us that adenosine triphosphate contains
three phosphate groups.
As a result of containing one more phosphate (and the high energy bond that attaches it),
adenosine triphosphate has more energy than adenosine diphosphate.
A large amount of energy must be used to attach another phosphate to ADP; this means that when a phosphate is removed from ATP,
a large amount of energy will be released.
This is the energy that is used for virtually all cell activities that require energy.
3. A heterotroph is an organism that can not produce its own food.
Since most food is produced by photosynthesis, the term heterotroph is usually applied to organisms that do not carry out photosynthesis.
In contrast, autotrophs are ``self-nourishing.'' They can conduct photosynthesis and produce their own food.
Recall that the primary products of photosynthesis are molecules of *carbohydrates*, which are used as energy sources and building materials by many different organisms.
4. One molecule of glucose contains 6 atoms of carbon, 12 atoms of hydrogen, and 6 atoms of oxygen.
A molecule of glucose contains much more energy than one molecule of carbon dioxide. (One molecule of glucose actually contains more energy than 6 molecules of carbon dioxide.) 5-6.
The process of oxidation usually results in the loss of electrons; since the lost electrons carry away energy, an oxidized molecule loses energy.
In contrast, when a molecule is reduced, it
gains an electron
and the energy that the electron brings with it.
7. Molecules of nicotinamide adenine dinucleotide (NAD) serve as sites for the temporary storage of energy and for the transportation of this energy from one site, or reaction, to another site, or reaction.
This energy is in an electron of hydrogen , so that the reduced form of NAD (i.e., the high energy version) is written NAD-H.
9. One molecule of glucose contains more energy than two molecules of pyruvic acid.
10. The term ``glycolysis'' refers to the splitting (or lysis) or glucose molecules.
11. The enzymes for glycolysis are located in the cytoplasm; they are not associated with any particular organelle.
12. No environmental oxygen is used during glycolysis; therefore, glycolysis is anaerobic.
(Keep in mind that this does not mean that no oxygen is present in any of the involved molecules; most of them (such as glucose) do contain oxygen.)
13-14. The term ``aerobic'' literally means ``with air.'' As used in cellular respiration, it refers to
the removal of oxygen from the environment of an organism and the use of that oxygen in some activity, such as cellular respiration.
In contrast, ``anaerobic'' refers to an absence of oxygen. (Keep in mind that the ``environment'' of an organism may be either air or water.)
15. Products of glycolysis include adenosine triphosphate, pyruvic acid, and reduced nicotinamide adenine dinucleotide (= NAD-H).
16. The end products of alcoholic fermentation include: adenosine triphosphate, carbon dioxide, and ethyl alcohol.
17-18. The alcoholic fermentation of one molecule of glucose results in the production of two molecules of carbon dioxide and two molecules of ethyl alcohol.
Remember, each time one molecule of ethyl alcohol is produced, one molecule of carbon dioxide is also produced.
19. No oxygen is used during the fermentation of glucose.
20. Alcoholic fermentation occurs in plants, fungi (such as yeasts), and bacteria but not in animals.
21. The reduced form of NAD would include an added hydrogen so it should be written as NAD-H; this form contains more energy than the oxidized form, NAD.
22. Lactic acid fermentation occurs in many animal cells and in some bacteria.
23. During lactic acid fermentation, lactic acid is produced from pyruvic acid.
24. One molecule of lactic acid contains three carbon atoms. Both pyruvic acid and lactic acid contain three carbon atoms, but lactic acid contains more energy.
Why? (Clue: what has been added to the pyruvic acid as it is being converted into lactic acid?)
25. Since lactic acid fermentation is anaerobic, no environmental oxygen is used.
26. Lactic acid is produced by enzymes in the cytoplasm; these enzymes are not attached to an organelle.
27. After lactic acid is formed it may accumulate and cause the symptoms we associate with fatigue.
When atmospheric oxygen becomes available , the lactic acid is converted back into pyruvic acid, and aerobic respiration (Kreb's cycle and the electron transport system) removes much of the energy stored in lactic acid.
28. One molecule of glucose and two molecules of lactic acid have the same number of carbon atoms (six).
However, one molecule of glucose has more energy than two molecules of lactic acid. Remember, when glucose is split, some energy is released (and part of this energy is used to manufacture molecules of ATP).
29. The two end products of lactic acid fermentation are molecules of ATP and lactic acid.
30. The presence of lactic acid in the human body is partially responsible for the tired feeling that we call fatigue and for the subsequent muscle aches and pains that accompany too much strenuous exercise or activity.
31. The products of fermentation (either ethyl alcohol, carbon dioxide, and ATP or lactic acid and ATP) are determined by the types of enzymes present in an organism.
The types of enzymes are primarily controlled by the genetic information that is present in the DNA of the genes (which are parts of the chromosomes).
32. If oxygen is present for respiration, the pyruvate (= pyruvic acid) molecules produced from glucose are converted into molecules of A. acetate; this involves the production and release of molecules of B. NAD-H and C. carbon dioxide.
The molecule named in _A_ (acetate) will be moved from the part of the cell called the D. cytoplasm into the cell organelle called the E. mitochondrion.
33. A mitochondrion is surrounded by two membranes. These membranes are simply referred to as the outer membrane and the inner membrane.
34. The inward projecting folds of the inner membrane of a mitochondrion are called cristae.
35. Two acetate groups are produced from one glucose. Each acetate contains two carbon atoms. Two carbon dioxide molecules are also released.
36. The Kreb's cycle occurs in the mitochondria.
37. The Kreb's cycle occurs in the matrix of the mitochondria. The matrix is the ``filler'' material inside the inner membrane.
38. The electron transport system (ETS) occurs on the cristae of the mitochondria.
39. The enzymes that control the reactions of the electron transport system are located on the cristae of the mitochondria.
Remember, in most cases the location of the enzymes determines where the reactions will occur.
40. The initial events in the Kreb's cycle involve the combination of a four carbon molecule with acetate to produce a molecule that is named A. citric acid and that contains B. six carbon atoms.
(Because citric acid is the first molecule produced in this series of events, many people refer to the series as the citric acid cycle rather than the Kreb's cycle.)
41. During Kreb's Cycle, molecules of citric acid, which have A. six atoms of carbon, are B. oxidized to regenerate the starting materials, which were 4 carbon molecules.
42. During the oxidation of citric acid back to the four carbon beginning material in the Kreb's Cycle, substances released include:
A. low energy molecules of a waste material called A. carbon dioxide;
B. a small number of molecules of B. ATP which can be directly used to supply energy for cell activities;
C. the carrier molecules called C. NAD and D. FAD which have been E. reduced by the addition of atoms of F. hydrogen obtained from citric acid and become NAD-H and FAD-H2
43. The carrier molecules NAD and FAD are important in the Kreb's cycle because these molecules can pick up, temporarily store, and safely transport high-energy electrons from the Kreb's cycle to the electron transport system.
44. The carrier molecules NAD and FAD, after being reduced to NAD-H and FAD-H2 during the Kreb's cycle will move to the part of the mitochondrion called the cristae.
45. In the electron transport system (=ETS), molecules of a substance called A. adenosine triphosphate (= ATP), which supplies energy for cell activities, are produced by the B. oxidation (= ``removal of energy from'') of carrier molecules and the subsequent removal of energy from atomic structures called C. electrons.
46. The aerobic respiration of one molecule of glucose results in the net gain of approximately 36 molecules of ATP. (I indicate ``approximately'' 36 because under some conditions a slightly different number can be produced.)
47. The low energy electrons released at the end of the ETS combine with ions of A. hydrogen; these newly formed atoms then combine with atoms of B. oxygen to produce molecules of C. water, one of the end products of aerobic respiration.
48. The primary function of cellular respiration is:
C. transfer energy from storage molecules such as glucose to useable molecules (ATP).
Remember, no biological process can ``make'' or ``destroy'' energy.
49. A cell that cannot respire cannot produce molecules of ATP. Without ATP, the cell cannot carry out activities that require energy. Consequently, the cell will die (quickly!).
50. The number of mitochondria present in a cell is related to the cell's activities and the amount of ATP being used.
Active cells (such as muscle cells and nerve cells) typically contain many more mitochondria than do less active cells (such as fat storage cells).
51. Approximately 40% of the energy stored in glucose is captured and stored in ATPs during aerobic respiration.
While this may seem low and inefficient (i.e., 60% is not captured), few human engineered processes are even close to being that efficient.
Now about #7..and the electron in hydrogen...can someone help me with understanding the hydrogen ATOM? Does hydrogen function as the ultimate basic electron (temporary) donor to transfer/supply energy?
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