Biology--Chapter 6

How do the mitochondria of brown fat cells differ from those of other cells?

Ion channels in the inner mitochondrial membrane prevent the formation of a H+ gradient. These channels dissipate the H+ gradient that the electron transport chain had produced. Without that gradient, ATP synthase cannot make ATP, and all the energy from the burning of fuel molecules is released as heat.

Sports physiologists at an Olympic training center want to monitor athletes to determine at what point their muscles begin to function anaerobically. They could do this by checking for a buildup of _____.

lactic acid. In humans, muscle cells switch to lactic acid fermentation after becoming anaerobic

In cellular respiration, glucose _____ electrons, whereas _____ electrons.

loses ... oxygen gains. During cellular respiration, glucose loses electrons and oxygen gains electrons. Oxidation and reduction always go together, as electron transfer requires both a donor and an acceptor.

A molecule that functions as the electron donor in a redox reaction __________.

loses electrons and becomes oxidized. In cellular respiration, glucose is oxidized when it loses electrons in hydrogen atoms. Oxygen is reduced as it gains electrons attached to hydrogen atoms.

Lungs are to breathing as _____ are to cellular respiration.

mitochondria. Two of the three main stages of cellular respiration occur in the mitochondria.

A scientist wants to study the enzymes of the citric acid cycle in eukaryotic cells. What part of the cell would she use as a source of these enzymes?

mitochondrial matrix. The water-soluble citric acid cycle intermediates and enzymes of a eukaryotic cell are found in the mitochondrial matrix, where the newly synthesized NADH and FADH2 diffuse to proteins of the electron transport chain held within the inner mitochondrial membrane. The matrix corresponds to the cytoplasm of the bacterium from which mitochondria are descended.

Bacteria have no membrane-enclosed organelles. However, some still generate ATP through cellular respiration. Where might the electron transport chain be found in these organisms?

plasma membrane. The electron transport chain requires a membrane that will act as a barrier to hydrogen ions that are being pumped across this space. The only membrane in a bacterial cell is the plasma membrane. Note that the inner membrane of a mitochondrion is a bacterial membrane obtained by the eukaryote through endosymbiosis.

Glycolysis is the only stage of cellular respiration that __________.

requires ATP to make ATP. Glycolysis contains an "investment" phase and a "payoff" phase. Two ATP are required to make four ATP.

Sunlight is essential for the varied life on Earth. Sunlight provides energy to photosynthetic organisms by providing __________.

the energy necessary to power the rearrangement of chemical bonds in H2O and CO2. This is what photosynthesis accomplishes in the conversion of water and carbon dioxide to sugars.

Oxidative phosphorylation could not occur without glycolysis and the citric acid cycle, because _____.

these two stages supply the electrons needed for the electron transport chain. The main function of glycolysis and the citric acid cycle is to supply oxidative phosphorylation with electrons carried by NADH and FADH2.

The energy production per acetyl CoA molecule through the citric acid cycle is __________.

1 ATP, 3 NADH, 1 FADH2. Then NADH and FADH2 go through the electron transport chain.

The overall efficiency of respiration is approximately __________.

34%. The rest of the energy released from glucose is converted to heat.

A. The following statements regarding glycolysis are TRUE. B. FALSE

A. 1. Glycolysis does not require compartmentalization by internal membranes 2. Glycolysis plays a role in both fermentation and respiration. 3. Glycolysis is the most widespread metabolic pathway found in Earth's life. B. Glycolysis evolved in an oxygen-rich environment. Correct, this is the FALSE statement. Glycolysis does not require O2, and likely evolved nearly a billion years before oxygen began accumulating from photosynthesis.

Why is the citric acid cycle called a cycle?

Acetyl CoA binds to oxaloacetate and this compound is restored at the end of the cycle. The cycling referred to is that of the resynthesis of the four-carbon compound. One turn of the citric acid cycle is completed with the regeneration of oxaloacetate, which is then ready to start the next cycle by accepting an acetyl group from acetyl CoA.

Which of the following best describes the electron transport chain?

Electrons pass from one carrier to another, releasing a little energy at each step. these electrons from one molecule to another, releasing a small amount of energy at each step.

Through respiration, humans breathe in O2 and breathe out CO2. However, what would happen if we did not breathe in O2?

We would not make enough ATP to meet our energy requirements. The electron transport chain accepts electrons from the breakdown products of glycolysis and the citric acid cycle, and it passes these electrons from one molecule to another until they are passed (along with two hydrogen ions) to oxygen to form water.

Using the ATP generated during cellular respiration, the intermediates of glycolysis and the citric acid cycle, such as pyruvate and acetyl CoA, can be siphoned off and used to __________.

build amino acids, fats, and sugars. The beauty of many metabolic pathways is that they can be used for both the breaking down of compounds for energy, or to synthesize complex macromolecules, depending on the needs of the cell and the availability of energy.

The O2 required for __________ is supplied by __________.

cellular respiration ... breathing cellular respiration ... ATP breathing ... cellular respiration. Breathing supplies the O2 required for cellular respiration, and also disposes of the CO2 produced as a waste product during cellular respiration.

The function of cellular respiration is to _____.

extract usable energy from glucose; The most prevalent and efficient energy-yielding pathway is cellular respiration, in which oxygen is consumed as a reactant, along with the organic fuel (frequently glucose).

During cellular respiration, glucose is oxidized. However, an intermediate __________ can be siphoned off and used to synthesize fats.

glyceraldeyhyde 3-phosphate. Glyceraldeyhyde 3-phosphate (G3P) is used in the synthesis of glycerol, which is a constituent of fats

A chemist has discovered a drug that blocks phosphoglucoisomerase, an enzyme that catalyzes the second reaction in glycolysis. He wants to use the drug to treat people with bacterial infections. However, he can't do this because _____.

human cells also perform glycolysis; the drug might also poison them. The chemist's drug could have a devastating effect on human cells

Where does glycolysis occur in a eukaryotic cell?

in the cytoplasmic fluid

When a car engine burns gasoline, the results of the reaction are similar to when cells burn glucose. Both reactions release carbon dioxide and water. In cells, the chemical energy in food is converted to ATP and heat. In a moving car, the chemical energy in gasoline is converted to __________.

kinetic energy and heat. About 25% of the energy released from the gasoline consumed by a car is converted to the kinetic energy of the moving car. The rest is given off as heat, which explains why car engines become so hot.

A gram of fat oxidized by cellular respiration produces approximately __________ as much ATP as a gram of carbohydrate.

twice. Fats are excellent fuels because they store so much energy for their mass.

Fat is the most efficient molecule for long-term energy storage, even compared to carbohydrates, because _____.

with their numerous hydrogen atoms, fats provide an abundant source of high-energy electrons. Because oxidative phosphorylation depends on a source of electrons (all of which are extracted from hydrogen atoms), fats, which contain primarily hydrogen and carbon atoms, are an abundant source of high-energy electrons that can be harvested for energy production.