1 In the absence of oxygen, cells consume glucose at a high, steady rate. When oxygen is added, glucose consumption drops precipitously and is then maintained at the lower rate. Why is glucose consumed at a high rate in the absence of oxygen and at a low rate in its presence?
2 In the following diagram showing the distribution of thermal energy in a population of substrate molecules, the energy thresholds indicated by numbers represent ...
A.the activation energy at high and low temperature.
B.the reaction rate at high and low pH.
C.the activation energy with and without an enzyme.
D.the reaction rate at high and low substrate concentrations.
E.the activation energy at high and low substrate concentrations.
3 Sort the following molecules from a low to high rate of diffusion inside the cytosol. Your answer would be a four-letter string composed of letters A to D only, e.g. ADCB.
(A)Myoglobin (a protein)
(B)Glycine (an amino acid)
(C)Ribosome (a protein–RNA complex)
4 Which of the following represents an “activated” carrier molecule?
5 ATP is the main energy currency in cells, and it can especially be used to drive condensation reactions that produce macromolecular polymers. How does ATP normally catalyze the condensation reaction, which by itself is energetically unfavorable?
A.It transfers its terminal phosphate to an enzyme and is released as ADP.
B.It transfers its two terminal phosphates to an enzyme, and is released as AMP.
C.It covalently attaches to both of the substrates.
D.It transfers either one or two terminal phosphate(s) to one of the substrates and is released as either ADP or AMP.
E.It covalently attaches to the enzyme, forming an enzyme–AMP adduct.
6 Which of the following elements is not normally found in cells?
7 A hydrophobic molecule is typically …
A.able to form hydrogen bonds with itself but not with water.
B.able to form hydrogen bonds with water.
D.hard to dissolve in a solvent.
E.incapable of interacting favorably with water.
8 For each of the following pairs, indicate whether they interact via hydrogen bonds (H) or ionic bonds (I), or do not favorably interact (N). Your answer would be a four-letter string composed of letters H, I, and N only, e.g. HNNI.
( )ATP and Mg2+
( )Urea and water
( )Glucose and the enzyme hexokinase (which uses glucose as a substrate)
( )A phospholipid tail and inorganic phosphate
9 Which of the following chemicals do you NOT expect to be readily dissolved in water?
10 Weak noncovalent attractions in the cell can be very strong in a nonaqueous environment. Some of these attractions are as strong as covalent interactions in a vacuum (their bond energy is approximately 340 kJ/mole), but become more than twenty-five times weaker (their bond energy becomes approximately 13 kJ/mole) in water. What type of attraction shows this phenomenon?
C.van der Waals attractions
E.All of the above
11 The cell can change the pH of its internal compartments using membrane transport proteins that pump protons into or out of a compartment. How many protons should be pumped into an endocytic vesicle that is 10–15 liters in volume and has a neutral pH in order to change the pH to 5? Avogadro’s number is 6 × 1023. Omit complications such as the membrane potential, buffers, and other cellular components.
12 The molecules inside the cell constantly collide with other molecules and diffuse through the cytoplasm in a random walk. The average net distance traveled by such a molecule after a certain time period t is proportional to the square root of t, i.e. (t)0.5, as well as to its diffusion coefficient. If, on average, it takes a molecule 100 milliseconds to travel a net distance of 0.5 µm from its starting point, how long would it normally take for the same molecule to travel a net distance of 5 µm from the same starting point?
13 In an enzymatic reaction involving NADH or NADPH, reduction of a substrate accompanies the oxidation of these carrier molecules to NAD+ or NADP+, respectively. What else typically happens in such a reaction?
A.A molecule of water is released to the solution upon completion of the reaction.
B.A proton is released during the oxidation of the carriers.
C.A proton is taken up by the substrate that is being reduced.
D.A proton is taken up by the carrier molecule that is being oxidized.
E.A phosphate group is transferred to the substrate.
14. The three families of cellular macromolecules are polymerized and depolymerized by a general mechanism involving water. Each of them has a set of monomers whose polymerization changes the total free energy of the system. Which of the following statements is true regarding these macromolecules?
A.Each polymerization step requires free-energy input and proceeds by the consumption of one water molecule.
B.Each depolymerization step requires free-energy input and proceeds by the consumption of one water molecule.
C.Each polymerization step requires free-energy input and proceeds by the release of one water molecule.
D.Each depolymerization step requires free-energy input and proceeds by the release of one water molecule.
firstly the figure as you mantioned is not observed, i am trying to answer as manny as possible.
1.Without oxygen (in anerobic respiration) molecules of ATP generated during metabolism is low (2 ATP), while in presence of oxygen (aerobic respiration) energy generation from glucose is as high as up to 36 ATP. Hence in the presence of oxygen more glucose molecules metabolize and generate more energy from glycolysis. Hence as we consume more energy during respiration more glucose is used to generated energy.
3. BCAD low to high rate of diffusion.
4. NADH is a activated molecule. because it can further slip in reaction (A = B+C) and can release energy.
5. terminal phospate group is highly unstable in ATP and removal of terminal phospate group release energy and convert it to ADP
hence B. it transfer it terminal phosphate to enzyme and release as ADP
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