Exam 2 study guide Flashcards
Reactions release free energy are:
exergonic and spontaneous
enzymes speed up reaction by
lowering activation energy necessary to initiate the reactions
When NADP is converted to NAD + and H+ and NADH+ has been
Oxidized
The net product of glycolysis are
2 pyruvate, 2 ATP and 2 NADH
The abilit y to diagnose tumor s using 18 F (FDG) is based on the phenomenon the most types of cancer cells exhibit higher level of
glycolysis
a general reason for cell signaling is
respond to environment changes and cell to cell communication
A type of cell signaling that involves signaling molecules
Endocrine
Which is correct order for three stages of cell signaling
Receptor Activation
Signal transduction
Cellular response
When a ligand binds to a receptor
receptor undergo a conformational change
A receptor has Kd for its ligand of 50nM at a ligand concentration of 100nm
most receptors will have ligand bound to them
When a signaling molecules binds to an enzymes-linked receptor it cause
the receptor to bind to a G protin
The receptor to become catalytically active
After a G-Protein couple receptor is activated when G-proteins make its active
All of the following:
REceptor binds to G protein
G protein exchanges GDP for GTP
G protein dissociates into a and b/y subsuntis
Prior to the binding of estrogen, the estrogen receptor is located
In the ER
Upon binding of EGF the EGF receptor first activates
Relay proteins
One way to turn off EGF patyhway is for the Ras portein, to hydroplyze GTP to GDP . How would affect EGF singal transduction pathway?
The pathway would be kept longer than it should and cell division would be accelerated
The enzyme that responsible for synthesis of cAMP is
Adenyl cyclase
The synthesis of cAMP can amplify the signal causd by a fist messenger becayse
Many cAMP molecules
many PKA are activated, phos. many target proteins
An agent that allows a cell to respond to changes in its environment is termed
a signal
When a cell secretes signaling molecules that bind to receptors on neighboring cells as well as the cell itself, this is called __________ signaling.
autocrine
Which of the following is not an example of a cell surface receptor?
the estrogen receptor
The EGF receptor functions as
a receptor tyrosine kinase.
The benefit of second messengers in signal transduction pathways is
an increase in the speed of a cellular response.
amplification of the signal.
After you eat a meal, a rise in glucose levels in the blood triggers the pancreas to release insulin. The insulin then binds to receptors on the surface of fat and muscle cells and leads to a cellular response in which those cells are better able to take up glucose. This form of cell signaling is an example of
endocrine signaling.
In Chapter 6, we considered how the binding of substrate to an enzyme has an analogy to a lock and key. Similarly, such an analogy can be applied to a receptor. After a key is placed into a keyhole, the turning of the key causes the lock to become unlocked. With regard to a receptor, the event of the lock becoming unlocked is analogous to
the conformational change in the receptor after it binds to a signaling molecule.
A receptor has a Kd for its ligand of 50 nM. This receptor
- Will be mostly bound by its ligand when the ligand concentration is 100 nM.
- Has a higher affinity for its ligand compared to a receptor with a Kd of 100 nM.
Certain anticancer drugs are used because they inhibit signal transduction pathways that are activated by growth factors. Which of the following would not be a good target for such a drug?
a G-protein-coupled receptor
A mutation in the gene that encodes the α subunit of a G protein causes the α subunit to bind more tightly to the β/γ dimer. Predict the effects of this mutation on the ability of the G-protein-coupled receptor to activate the signal transduction pathway and to promote a cellular response.
This mutation would inhibit the activation of the signal transduction pathway and inhibit the cellular response.
heterotroph is an organism that
cannot make organic molecules starting with inorganic molecules
* must consume autotrophs or other heterotrophs to survive
if you were traveling from cytosol to the thylakoid lumen how many membranes would you have to cross
3
The products of light reaction of photosynthesis include
NADPH
ATP
O2
When a photoexcited electron returns to the ground state, which of the following will not occur?
1) It could give off light.
2) It could absorb a photon of light.
3) It could give off heat.
4) All of the above are possible.
2) It could absorb a photon of light.
During linear electron flow, the primary function of photosystem I (PSI) is to make
1) ATP.
2) NADPH.
3) O2.
4) glucose.
5) all of the above.
2) NADPH.
What is the purpose of cyclic photophosphorylation, which involves photosystem I but not photosystem II?
A) production of ATP
B) production of NADPH
C) production of both ATP and NADPH
D) production of O2
E) production of ATP and O2
B) production of ATP
What is the purpose of cyclic photophosphorylation, which involves photosystem I but not photosystem II?
A) production of ATP
B) production of NADPH
C) production of both ATP and NADPH
D) production of O2
E) production of ATP and O2
A) production of ATP
After a chlorophyll pigment is the light harvesting complex of PSII absorbs a photo of light
energy is transferred to P680 via resonance energy transfer
Aftr P680* becomes P680+, it is converted back to P680
by receiving an electron from water
During Calvin cycle what is used to reduce carbon
NADPH
What happens during the phase of Calvin cycle called carbon fixation
CO2 is incorporated into an organic molecule.
under hot and dry conditions, why does the level of O2 within leaves because higher but the level of CO2 becomes lower?
Because the stomata are closed
An evolutionary adaptation to minimize photorespiration is found in
- C4 plants with mesophll and bundle sheath cells
* CAM plants that separate carbon fixation and the Calvin cycle in time
In PSII, P680 differs from the pigment molecules of the light-harvesting complex in that it
A) absorbs light energy and transfers that energy to other molecules without the transfer of electrons.
B) transfers an excited electron to the primary electron acceptor.
C) transfers an electron to O2.
D)acts as an ATP synthase to produce ATP.
E) is a carotenoid.
C) transfers an electron to O2.
During linear electron flow, the high-energy electron from P680
A) eventually moves to NADP+.
B) becomes incorporated into water molecules.
C) is pumped into the thylakoid space to drive ATP production.
D) provides the energy necessary to split water molecules.
E) falls back to the low-energy state in photosystem II.
A) eventually moves to NADP+.
The NADPH produced during the light reactions is used during
A) the carbon fixation phase, which incorporates carbon dioxide into an organic molecule of the Calvin cycle.
B) the reduction phase, which produces carbohydrates in the Calvin cycle.
C) the regeneration of RuBP of the Calvin cycle.
D) all of the above.
E) a and b only.
B) the reduction phase, which produces carbohydrates in the Calvin cycle.
The majority of the G3P produced during the reduction and carbohydrate production phase is used to produce
A) glucose.
B) ATP.
C) RuBP to continue the cycle.
D) rubisco.
E) all of the above
C) RuBP to continue the cycle.
Photorespiration is minimized in C4 plants because
A) these plants separate the formation of a four-carbon molecule from the rest of the Calvin cycle in different cells.
B) these plants carry out only anaerobic respiration.
C) the enzyme PEP carboxylase functions to maintain high CO2 concentrations in the bundle-sheath cells.
D) all of the above.
E) a and c only.
E) a and c only.
18O is a rare and stable isotope of oxygen. Let’s suppose you can expose plants to the following oxygen-containing compounds in which the oxygen atoms are in the form of 18O. Which of them would result in the production of O2 containing 18O-labeled oxygen?
A) CO2
B) glucose
C) H2O
D) CO
E) both a and b
C) H2O
Herbicides, such as atrazine, are thought to inhibit plant growth by blocking the ability of QB to accept electrons from QA. Atrazine would be expected to inhibit the production of
A) NADPH.
B) oxygen.
C) ATP.
D) all of the above.
E) a and c only.
E) a and c only.
Paraquat is an herbicide that competes with Fd (ferredoxin) for the electrons that are released from PSI after it is struck by light. In other words, paraquat can accept electrons from PSI. Paraquat would be expected to inhibit the production of
A) NADPH. B) oxygen. C) ATP. D) all of the above. E) a and c only.
A) NADPH.
The Calvin cycle turns one time for each molecule of carbon dioxide that enters the cycle. How many times must the Calvin cycle turn to produce two glucose molecules?
A) 1 B) 2 C) 12 D)24 E) 48
C) 12
As in the experiment by Calvin, 14C-labeled carbon dioxide was added to a liquid medium containing algae. In which organic molecule will the 14C-label first appear?
A) 3-phosphoglycerate
B) glyceraldehyde-3-phosphate
C) ribulose bisphosphate
D) 1,3-bisphosphoglycerate
E) glucose
A) 3-phosphoglycerate
When a reaction or process is exergonic,
A) it is spontaneous.
B) it does not need added energy to proceed.
C) the entropy usually increases.
D) the free-energy change is negative.
E) all of the above are correct.
E) all of the above are correct.
Cells often use ATP hydrolysis to
A) decrease their water content. B) drive endergonic reactions. C) prevent exergonic reactions. D) achieve chemical equilibrium. E) do all of the above.
B) drive endergonic reactions.
The main effect of enzymes on a chemical reaction is to
A ) lower the activation energy and thereby increase the rate of the reaction.
B) raise the activation energy and thereby increase the rate of the reaction.
C) lower the activation energy and thereby make the free energy more negative.
D) raise the activation energy and thereby make the free energy more positive.
E) do both a and c.
A ) lower the activation energy and thereby increase the rate of the reaction.
An inhibitor raises the KM for an enzyme but has no effect on the Vmax. This inhibitor probably binds to
A) the active site.
B) an allosteric site.
C) the substrate.
D) all of the above.
E) both a and b.
A) the active site.
A general reason for the catabolism of organic molecules is
- The recycling of building blocks
* The synthesis of energy intimidates such as ATP
The reaction Ae’ + B -> A + Be’
A has been oxidized and B has been reduced
The breakdown of glucose commonly occur in which of the following orders
glycolysis breakdown of pyruvate, the citric acids cycle, oxidative phosphorylation
During glycolysis, ATP is used during the ____ phase and ATP is synthesized during the _______ phase
Energy investment, energy liberation
Which of the following is not a product of glycolysis
CO2
Which of the following is not a product of the breakdown of pyruvate
ATP
During Citric acid cycle, what happen to carbon
- Organic carbon is release as inorganic carbon dioxide
* Carbon oxidized is make NADH and FAPH2
The electrons that travel down the electron transport chain come from
NADH and FADH2
The source of energy that directly drive the synthesis of ATP during Oxidative phosphorylation is
The H+ gradient
The spinning of the y subunit of ATP synthase is cause by
the hydrolysis of ATP
Advantage of connecting metabolic pathways for carbohydrate, protein and fat metabolism is that
The efficiency is higher because the same enzyme are used to break down different starting materials
Compare with oxidative phosphorylation in mitochondria, anaerobic respiration in bacteria differs in that
something other than O2 acts as final electron acceptor of the ETC
Reactions that release free energy are
A) exergonic.
B) spontaneous.
C) endergonic.
D) endothermic.
E) both a and b.
E) both a and b.
Enzymes speed up reactions by
providing chemical energy to fuel a reaction.
A) lowering the activation energy necessary to initiate the reaction.
B) causing an endergonic reaction to become exergonic.
C) substituting for one of the reactants necessary for the reaction.
S) doing none of the above.
B) causing an endergonic reaction to become exergonic.
The net products of glycolysis are
A) 6 CO2, 4 ATP, and 2 NADH.
B) 2 pyruvate, 2 ATP, and 2 NADH.
C) 2 pyruvate, 4 ATP, and 2 NADH.
D) 2 pyruvate, 2 GTP, and 2 CO2.
E) 2 CO2, 2 ATP, and glucose.
B) 2 pyruvate, 2 ATP, and 2 NADH.
The ability to diagnose tumors using [18F]-fluorodeoxyglucose (FDG) is based on the phenomenon that most types of cancer cells exhibit higher levels of
A) glycolysis. B) pyruvate breakdown. C) citric acid metabolism. D) oxidative phosphorylation. E) all of the above.
A) glycolysis.
For the idealized reaction
aA+bB ⇋ cC+dD,
let’s suppose that the equilibrium constant, Keq, is 0.01. If the starting concentrations for A, B, C, and D are 1 M each, what would you predict based on the value of Keq?
A) The forward reaction is favored. B) The reverse reaction is favored. C) The forward reaction is fast. D) The reverse reaction is fast. E) Both b and d are correct.
B) The reverse reaction is favored.
Reaction 1 is
A + B ⇋ C + H 2 O. It is endergonic with ΔG = 4.6 kcal/mol.
Reaction 2 is
ATP + H2O ⇋ ADP +Pi . It is exergonic with ΔG = −7.3 kcal/mol.
What is the overall free energy for the following coupled reaction:
A + B + ATP ⇋ ADP + Pi + C?
A) 0 kcal/mol
B) −2.7 kcal/mol
C) +2.7 kcal/mol
D) −11.9 kcal/mol
E) +11.9 kcal/mol
B) −2.7 kcal/mol
Succinate dehydrogenase is an enzyme in the citric acid cycle that catalyzes a reaction that converts succinate to fumarate (see Figure 6.17). A molecule called malonate acts as an inhibitor of succinate dehydrogenase. The presence of malonate raises the KM for succinate but does not affect the Vmax of the reaction. Malonate
A) is a competitive inhibitor.
B) is a noncompetitive inhibitor.
C) binds to the active site of the enzyme.
D) binds to an allosteric site of the enzyme.
E) Both a and c are correct
B) is a noncompetitive inhibitor.
An insecticide called rotenone inhibits NADH dehydrogenase, which is involved in the first step of the electron transport chain (ETC). Rotenone blocks the ability of NADH dehydrogenase to accept electrons from NADH and inhibits ATP synthesis. What is the mechanism by which rotenone inhibits ATP synthesis?
A) Rotenone prevents the synthesis of O2.
B) Rotenone inhibits the formation of an H+ electrochemical gradient.
C) Rotenone directly inhibits ATP synthase.
D) Rotenone prevents FADH2 from donating electrons to the ETC.
E) Rotenone prevents the reduction of NAD+ to NADH.
B) Rotenone inhibits the formation of an H+ electrochemical gradient.
Certain drugs act as ionophores that cause the mitochondrial membrane to be highly permeable to H+. How would such drugs affect oxidative phosphorylation?
A) Movement of electrons down the ETC would be inhibited.
B) ATP synthesis would be inhibited.
C) ATP synthesis would be unaffected.
D) ATP synthesis would be stimulated.
E) Both a and b are correct.
B) ATP synthesis would be inhibited.
