Flash Card Review Metabolism…
2011-12
1. Explain how C4 plant leaves differ structurally than C3 plantsC4 plants have bundle-sheath cells that are arranged into tightly packed sheaths around the
veins of the leaf. Between the bundle sheath and the leaf surface are the more loosely packed
mesophyll cells. However, the C3 plants have only the mesophyll cells between the veins and
the surface.
2. Explain how energy molecules are used in DNA replicationThe energy for this process of DNA polymerization comes from two of the three total
phosphates attached to each unincorporated base. (Free bases with their attached phosphate
groups are called nucleoside triphosphates.) When a nucleotide is being added to a growing
DNA strand, two of the phosphates are removed and the energy produced creates a
phosphodiester bond that attaches the remaining phosphate to the growing chain.
3. Describe Glycolysis- Glycolysis is the breaking down of glucose into two molecules of
pyruvate. It takes place in the cytoplasm. It the first step of cell respiration and the only step
that is anaerobic or doesn't require oxygen. What goes into glycolysis is (C6)(H12)(O6) which
is glucose, and two molecules of ATP. What comes out is 2NADH, 2 pyruvate and 4ATP.
Glycolysis is commonly known as sugar splitting because it splits a glucose molecule into two
pyruvate molecules.
4. Describe the oxidation of Pyruvate & the Krebs Cycle
Pyruvate is broken down to three CO2 molecules, including the molecule of CO2 released
during the conversion of pyruvate to acetyl CoA. The cycle generates 1 ATP per turn by
substrate-level phosphorylation, but most of the chemical energy is transferred to NAD+ and a
related electron carrier, the coenzyme FAD during the redox reactions. The reduced
coenzymes, NADH and FADH2, shuttle their cargo of high energy electrons to the electron
transport chain.
5. Describe the Electron transport chain and how it functions to make ATP
In the ETC, electrons from NADH and FADH2 lose energy in several energy-releasing steps. At
the end of the chain, electrons are passed to O2 reducing it to H2O. At certain steps along the
ETC, electron transfer causes protein complexes to move H+ from the mitochondrial matrix to
the intermembrane space, storing energy as a proton-motive force. As H+ diffuses back into
the matrix through ATP synthase, its passage drives the phosphorylation of ADP.
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6. Explain lactic acid fermentation.
Lactic acid fermentation is the process in which glucose, fructose, and sucrose are converted
into cellular energy and lactose. It is anaerobic, meaning that no oxygen is necessary to
complete this process. It occurs in the muscles. First, glucose is split into two pyruvate by a
process called glycolysis. Fermentation, a redox reaction, is then able to occur. Gylcolysis
reduces NAD+ to NADH. NADH then donates its extra electrons to pyruvate, thus regenerating
NAD+. Lactic acid is formed by the reduction of pyruvate.
7. Glycogen
A polysaccharide that is the primary form of glucose storage in human and animal cells
8. Describe how rate of respiration can be measured in an experiment
Seal the organism that you intend to test into a waterproof container with a graduated pipette
protruding from one end. Put a small amount of colored food die into the end of the pipette so that it
reaches to one of the markers on the pipette. Submerge the container and pipette in the water. The
water will not take the place of the air in the box and pipette. As the organism, preferably a plant,
takes in the air to breathe, the water and food coloring will slowly move down the pipette allowing you
to gauge how much air the organism took in. From there, since air is twenty-one percent oxygen,
convert the amount of air to oxygen and take that new number over time and you have the rate of
respiration.
9. Describe an experiment that measures net photosynthesis
Net photosynthesis is the total production of photosynthetic products minus the amount used up for
the plants own respiration needs. Fill a beaker with carbonated water and place a plant in it, this way
the plant still gets its carbon dioxide. Place an air tight funnel on top of the beaker that leads to a
graduated test tube. As the plant uses the carbon dioxide from the water, it will produce oxygen and
release it into the water. The water can only hold so much oxygen so make sure to oxygenate the
water first to fill it to capacity. Once the test tube goes on, chill it to condense the water vapor leaving
only the oxygen produced by the plant in the test tube. When time is up, the gas can be measured for
volume and temperature.
10. Glycolysis
Glycolysis is the first step of cellular respiration. It is the oldest process for creating ATP, the cell's
source of energy. Glycolysis converts a molecule of sugar into two molecules of pyruvic acid, two
NADH molecules and two ATP molecules. This process occurs in all organisms because cellular
respiration is necessary for life. This process is anaerobic because it does not require the presence of
oxygen to function properly. If the organism is anaerobic, it will process from glycolysis with alcohol or
lactic fermentation. If the organism is aerobic, it will proceed to the Kreb's cycle and then to the
electron transport chain to produce even more ATP molecules.
11. Explain how sunlight is used to make NADPH in photosynthesis
NADPH is created in the light reactions of photosynthetic organisms. The sunlight's wave lengths are
absorbed by the pigments inside the chloroplasts. That energy the light powers the splitting of water,
which gives electrons to the chlorophyll, causing the elections to bounce from one chlorophyll to
another until they reach the reaction center in photosystem II, which contains special chlorophyll
called P680. When the electrons reach the P680, they shoot up the reaction center and go into the
electron transport chain, which establishes a proton gradient used by ATP synthase to produce ATP.
The electron continues down the chain until it reaches photosystem I, which contains P700. More
light excites the electrons launching it up the reaction center in photosystem I. This time, as the
electron moves through the various proteins in the chain, they reduce NADP+ with the electron and a
proton to form NADPH. The NADPH moves on to the Calvin cycle with ATP to produce sugar.
12. Describe an experiment that tests the effect of a factor on respiration rate.
To test the effect of a factor on a seed's respiration rate, temperature for example, an
experiment should be conducted. The independent variable would be temperature, and the
dependent variable would be respiration rate. The control would be a plant kept at room
temperature. Another plant would be kept in a very cold environment, and one more would be
kept in a very hot environment. The plants should be kept in these environments for a few
days, all other factors held constant. The respiration rates of each plant should be measured
and compared with the others to obtain results.
13. Draw a graph showing the effect of enzymes on an endergonic reaction.
14. Explain how the energy of organic compounds is converted to ATP .
First, in cellular respiration (involving glycolysis, the citric acid cycle, and oxidative
phosphorylation), organic compounds such as glucose are oxidized, while oxygen is reduced. The
organic compound is broken down, and its electrons are usually first transferred to NAD+, a
coenzyme. NAD+ is the oxidizing agent in cellular respiration; it becomes NADH, stored energy that
will lead to ATP formation. Then, NADH passes electrons to the electron transport chain of the
oxidative phosphorylation stage--oxygen pulls electrons down the chain in an energy-yielding tumble,
and this energy is used to generate ATP.
15. Coenzyme
Coenzymes are organic cofactors. Cofactors are nonprotein helpers for enzymes—they
function in some way to allow catalysis to occur. Many coenzymes are derived from vitamins. An
example of a coenzyme is coenzyme A (CoA), which is an acetyl group carrier crucial in the Krebs
Cycle.
16. Explain alcohol fermentation.
Alcohol fermentation is completed by yeast and some kinds of bacteria. Alcoholic fermentation
begins after glucose enters the cell. The glucose is broken down into pyruvic acid, and pyruvate is
converted to ethanol, which releases carbon dioxide and oxidizes NADH in the process to create
more NAD+. NAD+ is the electron acceptor, rather than oxygen, in fermentation. Oxidative
phosphorylation occurs to generate ATP.
17. Photophosphorylation- The use of sunlight to produce ATP
18. Explain how H2O is used to make ATP in photosynthesis
-In photolysis in chloroplasts, water is broken down into oxygen and
hydrogen, yielding electrons. The transfer of electrons in pigments
drives the creation of an H+ gradient, which is then used to power the
creation of ATP
19. Explain how enzymes function:
Enzymes are biological catalysts that speed up chemical reactions in cells. They do this by
having a certain three-dimensional structure that fits the substrate. The substrate is enters the
enzyme where the reaction is sped up, then exits as something else, allowing the enzyme to
work on another substrate.
20. Explain how ATP and NADPH are used to build sugars in the Calvin Cycle:
The cycle spends ATP as an energy source and consumes NADPH2 as reducing power for
adding high energy electrons to make the sugar. Also, in Phase 2 of the cycle, ATP and NADPH2
from the light reactions are used to convert 3-phosphoglycerate to glyceraldehyde 3-phosphate,
the three-carbon carbohydrate precursor to glucose and other sugars.
21. Explain how temperature affects enzyme function:
The temperature is crucial because the enzyme can only work under certain conditions. If not,
it is denatured, or changes shape or size so that it doesn’t work anymore. Too extreme
temperatures can denature the enzymes.
22. Discuss how the structure of a protein affects enzyme activity.
Enzymes contain different domains that perform different functions. An example of a domain is
the active site. An inhibitor can bind to an active site on an enzyme, changing its shape and
preventing the substrate from binding to it. (This is competitive inhibition). This will prevent the
enzyme from catalyzing the reaction. Non-competitive inhibition is where the inhibitor reduces
the activity of the enzyme by binding to an enzyme (not on its active site). Although the binding
of the inhibitor does not prevent the binding of the substrate, it still changes the structure of the
enzyme and prevents it from producing products.
Also the 3D structure of an enzyme brings into position the chemical groups on the surface of
the protein. These groups form non-covalent interactions with the substrates in a way such that
when the interactions are made, the enzyme reshapes the substrate into the transition site.
That way, the amount activation energy is lessen because some of the energy was already
supplied by the non-covalent interactions between the enzyme and substrate.
23. Describe the allosteric regulation of an enzyme.
An allosteric enzyme is where the activity of an enzyme can be controlled by the binding of the
molecule to the allosteric site. (somewhere other than the active site). A positive allosteric
modification is the catalyzing of a molecule to the enzyme which can increase the rate of
reaction. A negative allosteric reaction is when the catalyzing of a molecule will decrease the
rate of reaction. An example is that phosphofructokinase is promoted by a high AMP
concentration and inhibited by a high ATP concentration.
24. Explain how a proton gradient is used to build ATP in photosynthesis.
In photosynthesis, the absorption of light leads to electron transfer across a membrane. For each
electron transfer, one excess hydroxide ion is generated inside the cell. The process produces a
proton gradient across the membrane that can drive ATP synthesis. Protons flow down this gradient
through ATP synthases to generate ATP.
25. Oxidative Phosphorylation- The production of ATP using energy derived from the redox
reactions of an electron transport chain. This is the third major stage of cellular respiration.
26. Explain how pH affects enzyme function.
Changes in pH may not only affect the shape of an enzyme but it may also change the shape or
charge properties of the substrate so that either the substrate cannot bind to the active site or it
cannot undergo catalysis. Extremes in pH can denature enzymes. In geneal enzyme have a pH
optimum. However the optimum is not the same for each enzyme.
27. Describe the structure of ATP.
 Consists of a purine base (adenine) attached to the 1' carbon atom of a pentose sugar
(ribose). Three phosphate groups are attached at the 5' carbon atom of the pentose sugar.
ATP is also incorporated into nucleic acids by polymerases in the processes of DNA replication
and transcription.
28. Explain the induced fit model of enzyme function.
 Specific substrates combine to a specific enzyme.
 The theory (basically) states that both enzyme and active site change shape so only a specific
substrate bind to the enzyme, creating the wanted products that the reaction creates.
29. Explain how a proton gradient is used to build ATP in cellular respiration.
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Most of the ATP is generated by the proton gradient that develops across the inner
mitochondrial membrane. The number of protons pumped out as electrons drop from NADH
through the respiratory chain to oxygen is theoretically large enough to generate, as they
return through ATP synthase, 3 ATPs per electron pair (but only 2 ATPs for each pair donated
by FADH2). The energy stored in the proton gradient is also used for the active transport of
several molecules and ions through the inner mitochondrial membrane into the matrix.
NADH is also used as reducing agent for many cellular reactions. The actual yield of ATP as
mitochondria respire varies with conditions. It probably seldom exceeds 30.
30. Describe how enzyme function can be measured in an experiment: Measure the rate of
the disappearance of the substrate. For example, the enzyme catalase breaks down H2O2 to
produce oxygen bubbles. When catalase is added to H2O2, bubbles are produced, showing
that an enzymatic reaction is occurring by the disappearance of the substrate, H2O2.
31. Describe the role of NADH and FADH2 in cellular respiration:
The energy produced in the Krebs Cycle is stored inside NADH and FADH2; then they travel to
the electron transport chain. As electron carriers, NADH and FADH2 assist with delivering needed
electrons through the electron transport chain. The chemical make-up of both molecules carries a
charge. During the electron transport chain, these charges are passed along through a series of
steps which end up creating H2 molecules. In the electron transport chain, NADH and FADH2
provide the energy needed to convert O2 molecules into H2O.
32.
Cytochrome: An iron containing protein that is a component of electron chains in the
mitochondria and chloroplasts of eukaryotic cells and the plasma membranes of prokaryotic
cells.
33. Explain how ATP serves as am energy currency molecule
The bonds between the phosphate groups in ATP can be easily broken by hydrolysis. When
the bonds are broken, this reaction is exergonic, meaning that it releases energy that the cell
can use. The release of energy mainly comes for the reactants (ATP and water). Since the
three phosphate groups of ATP are all negative charges, the repulsion between them leads to
a lot of stored energy.
34. Explain how sunlight is used to make ATP in photosynthesis
When sunlight enters the chloroplast, the light reactions occur in the thylakoids. By using the
process of photophosphorylation, chemiosmosis is used to power the the addition of a
phosphate group to ADP, forming ATP. The ATP is then used in the Calvin Cycle to make
sugar. The used ATP turns back into ADP, which leaves the Calvin Cycle and is converted
back into ATP in the light reactions.
35. Explain how salinity affects an enzyme function.
Enzymes are very sensitive to the salinity (or salt concentration) of their environment. Very
high or very low concentrations can cause the enzymes to denature and become useless
36. Describe the role of oxygen in cellular respiration: Without oxygen, cellular respiration
could not occur because oxygen serves as the final electron acceptor in the electron transport
system. The electron transport system would therefore not be available.
37. List and describe the function of all the enzymes of the digestive system:Digestive
enzymes break complex molecules into simpler ones that can be absorbed by cells
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Potassium bicarbonate (KHCO3): The major role of bicarbonate is to neutralize acidity
mainly in an attempt to preserve the dentin and tooth enamel and also to neutralize
bacterial toxins. Bicarbonate also prevents acid damage to the esophageal lining before
food enters the stomach.
lingual lipase: Lipid digestion initiates in the mouth. Lingual lipase starts the digestion of
the lipids/fats.
amylase: Carbohydrate digestion also initiates in the mouth. Amylase produced by the
salivary glands breaks complex carbohydrates to smaller chains, or even simple sugars.
It is sometimes referred to as ptyalin.
Mucin: Mucin functions to make food more pliable and also covers it facilitating its
transfer in the esophagus to the stomach, by lubricating the content.
lysozyme: Considering that food contains more than just the essential nutrients and
bacteria or viruses, the lysozome offers a limited and non-specific, yet beneficial
antiseptic function in digestion.
Pepsinogen is the main gastric enzyme. It is produced by the stomach cells called "chief
cells" in its inactive form pepsinogen, which is a zymogen. Pepsinogen is then activated
by the stomach acid into its active form, pepsin. Pepsin breaks down the protein in the
food into smaller particles, such as peptide fragments and amino acids. Protein
digestion, therefore, first starts in the stomach, unlike carbohydrate and lipids, which
start their digestion in the mouth.
Hydrochloric acid (HCl): This is in essence positively charged hydrogen atoms (H), or in
lay-terms stomach acid, and is produced by the cells of the stomach called parietal
cells. HCl mainly functions to denature the proteins ingested, to destroy any bacteria or
virus that remains in the food, and also to activate pepsinogen into pepsin.
Intrinsic factor (IF): Intrinsic factor is produced by the parietal cells of the stomach.
Vitamin B12 (Vit. B12) is an important vitamin that requires assistance for absorption in
terminal ileum. Initially in the saliva, haptocorrin secreted by salivary glands binds Vit. B,
creating a Vit B12-Haptocorrin complex. The purpose of this complex is to protect
Vitamin B12 from hydrochoric acid produced in the stomach. Once the stomach content
exits the stomach into the duodenum, haptocorrin is cleaved with pancreatic enzymes,
releasing the intact vitamin B12. Intrinsic factor (IF) produced by the parietal cells then
binds Vitamin B12, creating a Vit. B12-IF complex. This complex is then absorbed at the
terminal portion of the ileum.
Mucin: The stomach has a priority to destroy the bacteria and viruses using its highly
acidic environment but also has a duty to protect its own lining from its acid. The way
that the stomach achieves this is by secreting mucin and bicarbonate via its mucous
cells, and also by having a rapid cell turn-over.
Gastrin: This is an important hormone produced by the "G cells" of the stomach. G cells
produce gastrin in response to stomach stretching occurring after food enters it, and
also after stomach exposure to protein. Gastrin is an endocrine hormone and therefore
enters the bloodstream and eventually returns to the stomach where it stimulates
parietal cells to produce hydrochloric acid (HCl) and Intrinsic factor (IF).
Secretin, a hormone produced by the duodenal "S cells" in response to the stomach
chyme containing high hydrogen atom concentration (high acidicity), is released into the
blood stream; upon return to the digestive tract, secretion decreases gastric emptying,
increases secretion of the pancreatic ductal cells, as well as stimulating pancreatic
acinar cells to release their zymogenic juice.
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Cholecystokinin (CCK) is a unique peptide released by the duodenal "I cells" in
response to chyme containing high fat or protein content. Unlike secretin, which is an
endocrine hormone, CCK actually works via stimulation of a neuronal circuit, the endresult of which is stimulation of the acinar cells to release their content. CCK also
increases gallbladder contraction, resulting in bile squeezed into the cystic duct,
common bile duct and eventually the duodenum. Bile of course helps absorption of the
fat by emulsifying it, increasing its absorptive surface. Bile is made by the liver, but is
stored in the gallbladder.
38. Describe and diagram the regulation of body temperature in mammals:
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In humans, the optimum internal temperature (37 degrees Celsius) is kept constant throughout
the body by blood and the hypothalamus.
Blood picks up heat from active cells like muscles, and carries it elsewhere as it pulses through
the arteries, capillaries and veins.
The hypothalamus monitors internal temperature and communicates with effectors to keep the
body within safe limits (i.e. negative feedback mechanisms).
39. Energy Transfer: Explain how the hydrolysis of ATP is used to activate proteins.
Protein kinase phosphorylates, or transfers a phosphate group from ATP to, a protein. ATP hydrolysis
leads to a change in the protein's shape, allowing it to bind more easily to another molecule, and thus
activating it.
40. Substrate-level Phosphorylation
Substrate-level phosphorylation is the creation of ATP or GTP by the transfer of a phosphoryl group
to ADP or GDP from a phosphorylated intermediate metabolic compound.
41. organismal enzyme need - as catalysts to a great deal of chemical reactions, enzymes are
essential for sustaining life, as without them chemical reactions would not occur at rates
sufficient for life. Additionally, enzymes are used in a variety of complex life processes,
including metabolic pathways, signal transduction, muscle contraction, bioluminescence, etc
42. Explain how hydroloysis of ATP is used in macromolecule synthesis - adenosine
triphosphate holds a high energy yet fragile bond that, when broken (hydrolyzed), releases
relatively large amounts of energy. the energy released is used to bond molecules together,
creating macromolecules
43. Give an example of a common digestive enzyme:
Hydrochloric Acid (HCl)
44. Explain how the hydrolysis of ATP is used to move muscle:
The hydrolysis of ATP releases energy that allows muscles to
contract. ATP must be added to isolated actomyosin (consists of two
proteins, actin and myosin).
ATP + H2O --> ADP + P + energy and the relaxed muscle uses this energy
to contract.
45. Explain how H2O is used to make ATP in photosynthesis:
In photosynthesis (light reactions), one molecule of the pigment
chlorophyll loses an electron. That electron starts the flow of
electrons down the electron transport chain which leads to the
reduction of NADP to NADPH. This also creates a proton gradient across
the chloroplast membrane. The dissipation is used by ATP synthase for
the synthesis of ATP. Chlorophyll will regain the lost electron from a
water molecule through photolysis (it releases an O2 molecule).
46. Photosynthesis: the process by which CO2 and H2O are converted into C6H12O6. This occurs
in the chloroplasts in two step process. In the light reaction, electrons from H2O are used to
reduce NADP+ into NADPH and O2 is released. The hydrogen from water creates an electron
gradient. The potential energy is harnessed with the help of ATP Syntheses. The next step is
the Calvin Cycle( dark reaction) where the created ATP and NADPH is used to create sugar
from CO2.
47. Describe the electron transport chain and explain how it functions to make ATP: NADH
and FADH2 carry electrons to hydrogen pumps. The electrons successively fall from their
exited states; their energy is released is transferred to the proton pumps. The proton pumps
crate an electron gradient across the membrane. This activates the ATP synthesis which
allows protons to flow back, and using the potential energy created by the pumps to bond
together ADP and P+ to form ATP.
48. Explain alcoholic fermentation: fermentation is the partial degradation of sugar without the
use of oxygen. The process begins with glycolysis, but before entering the citric acid cycle.
The pyruvic acid is metabolized to ethyl alcohol through acetaldehyde.
49. How does the carbon fixation process differ for C4 plants?
4 plants use a method of metabolism that cuts down on waste that is caused by the enzyme Rubisco
fixing oxygen instead of Carbon Dioxide. Instead of the usual method of carbon fixation, C4 plants
use a different enzyme to fix Co2 in mesophyll cells and then in bundle-sheath cells. This separates
the Rubisco from the O2 an makes sure only Carbon is fixed for the plant to use in light
reactions. The carbon compounds are transferred to the Calvin Cycle.
50. How does the carbon fixation process differ for CAM plants?
CAM plants are adapted for arid conditions. The plants that use this metabolic pathway close their
stomata during the day to preserve water loss by preventing transpiration. After the carbon is taken
up through the stomata during the night, the CO2 is fixed into organic acids in the non-light reactions.
These organic acids are stored in the vacuoles in the plant. When the CO2 compounds are needed
for the light reactions (during the day) these acids are retrieved from the vacuoles and taken to the
chloroplasts to take part in the light reactions.
51. Cellular respiration is the set of the metabolic reactions and processes that take place in the
cells of organisms to convert energy from nutrients such as sugar into ATP. The reactions
involved in respiration are catabolic reactions, which break large molecules into smaller ones,
releasing energy in the process as they break high-energy bonds. Respiration is one of the key
ways a cell gains useful energy to fuel cellular activity, growth, reproduction and other plant
processes.
52. Chemiosmosis On one side of the membrane (we will call this side the "inside") is a supply of
hydrogen atoms. Special carrier molecules use the energy released in the electron transport
chain to bring hydrogen atoms close to the membrane and separate the hydrogen into H+ ions
and electrons. The electrons are brought back to the inside of the membrane while the H+ ions
are forced to the other side (the "outside"). As more and more H+ ions accumulate on the
outside of the membrane, two gradients are formed. First, a pH gradient is formed. This means
that the outside is more acidic (because it has H+ ions) than the inside of the membrane. Also,
an electrical gradient forms, since H+ ions have a positive charge.
When these gradients become sufficiently intense, they force the H+ ions through a channel
(sometimes called the F0 channel) in the membrane in a tremendous gush. The ions end up in a large
structure called the F1 unit where an enzyme called ATP synthtase is located. Also present in the F1
are ADP molecules and phosphate molecules. As the H+ ions rush by, they provide the energy which
brings the ATP synthtase, ADP, and phosphates together. The ATP synthtase bonds the ADP and
phosphate molecules, forming ATP. The H+ ions, now on the inside of the membrane, can be
transported by the carrier molecules across the membrane so that the process may be repeated
when enough energy is released from the electron transport chain.
53. CO2 usage in C3 plants for the production of sugars: Most plants put CO2 directly into the
Calvin cycle and the first stable organic compound formed is the glyceraldehyde 3-phosphate.
Since that molecule contains three carbon atoms, these plants are called C3 plants. The 6
CO2 molecules in the photosynthesis equation are broken up and the 6 atoms of carbon are
then used to make glucose (C2H12O6).