MasteringBio 3.04

28 terms by sramati 

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Which term describes the degree to which an element attracts electrons?

Electronegativity

Which of the following statements is true of the bonds in a water molecule?

Oxygen holds electrons more tightly than hydrogen does, and the net charge is zero.

Which of the following statements is not true of most cellular redox reactions?

A hydrogen atom is transferred to the atom that loses an electron.

Gaseous hydrogen burns in the presence of oxygen to form water:
2H2 + O2 → 2H2 O + energy
Which molecule is oxidized and what kind of bond is formed?

Hydrogen, polar.

In the net redox reaction in acetyl CoA formation and the citric acid cycle, pyruvate is oxidized to ___.

CO2

In the net redox reaction in acetyl CoA formation and the citric acid cycle, NAD+ is reduced to ___.

NADH

In the net redox reaction in acetyl CoA formation and the citric acid cycle, FAD reduced to ___.

FADH2

In the oxidation of pyruvate to acetyl CoA, one carbon atom is released as CO2. However, the oxidation of the remaining two carbon atoms—in acetate—to CO2 requires a complex, eight-step pathway—the citric acid cycle. Consider four possible explanations for why the last two carbons in acetate are converted to CO2 in a complex cyclic pathway rather than through a simple, linear reaction. It is easier to remove electrons and produce CO2 from compounds with three or more carbon atoms than from a two-carbon compound such as acetyl CoA.

True

In mitochondrial electron transport, what is the direct role of O2?

to function as the final electron acceptor in the electron transport chain

How would anaerobic conditions (when no O2 is present) affect the rate of electron transport and ATP production during oxidative phosphorylation? (Note that you should not consider the effect on ATP synthesis in glycolysis or the citric acid cycle.)

Both electron transport and ATP synthesis would stop.

NADH and FADH2 are both electron carriers that donate their electrons to the electron transport chain. The electrons ultimately reduce O2 to water in the final step of electron transport. However, the amount of ATP made by electrons from an NADH molecule is greater than the amount made by electrons from an FADH2 molecule. Why is more ATP made per molecule of NADH than per molecule of FADH2?

Fewer protons are pumped across the inner mitochondrial membrane when FADH2 is the electron donor than when NADH is the electron donor.

When the protein gramicidin is integrated into a membrane, an H+ channel forms and the membrane becomes very permeable to protons (H+ ions). If gramicidin is added to an actively respiring muscle cell, how would it affect the rates of electron transport, proton pumping, and ATP synthesis in oxidative phosphorylation? (Assume that gramicidin does not affect the production of NADH and FADH2 during the early stages of cellular respiration.)

remains the same: proton pumping rate, electron transport rate, rate of oxygen uptake. decreases or goes to zero: rate of ATP synthesis, size of protein gradient

In cellular respiration, most ATP molecules are produced by _____.

oxidative phosphorylation

The final electron acceptor of aerobic respiration in mitochondria is _____.

oxygen

During electron transport, energy from _____ is used to pump hydrogen ions into the _____.

NADH and FADH2 ... intermembrane space

The proximate (immediate) source of energy for oxidative phosphorylation is _____.

kinetic energy that is released as hydrogen ions diffuse down their concentration gradient

Recall that the complete oxidation of a mole of glucose releases 686 kcal of energy ( = -686 kcal/mol). The phosphorylation of ADP to form ATP stores approximately 7.3 kcal per mole of ATP. What is the approximate efficiency of cellular respiration for a "mutant" organism that produces only 29 moles of ATP for every mole of glucose oxidized, rather than the usual 36-38 moles of ATP?

30%

In liver cells, the inner mitochondrial membranes are about 5 X the area of the outer mitochondrial membranes, and about 17 X that of the cell's plasma membrane. What purpose must this serve?

It increases the surface for oxidative phosphoryation.

Exposing inner mitochondrial membranes to ultrasonic vibrations will disrupt the membranes. However, the fragments will reseal "inside out." These little vesicles that result can still transfer electrons from NADH to oxygen and synthesize ATP. If the membranes are agitated still further however, the ability to synthesize ATP is lost. After the first disruption, when electron transfer and ATP synthesize still occur, what must be present?

all of the electron transport proteins as well as ATP synthase

Which of the following couples chemiosmosis to energy storage?

ATP synthase

The oxygen consumed during cellular respiration is involved directly in which process or event?

accepting electrons at the end of the electron transport chain

An electron loses potential energy when it

shifts to a more electronegative atom.

When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a hydrogen ion) the molecule becomes

reduced

During aerobic respiration, electrons travel downhill in which sequence?

food -> NADH -> electron transport chain -> oxygen

When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the molecule becomes

oxidized

Why does the oxidation of organic compounds by molecular oxygen to produce CO2 and water release free energy?

Electrons are being moved from atoms that have a lower affinity for electrons (such as C) to atoms with a higher affinity for electrons (such as O).

During cellular respiration, acetyl CoA accumulates in which location?

mitochondrial matrix

Carbon dioxide (CO2) is released during which of the following stages of cellular respiration?

oxidation of pyruvate to acetyl CoA and the citric acid cycle

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