Biology Chapter 6 Test Review

These carrier molecules form an __________.

electron transport chain

An average adult human requires 2,200 kcal of energy per day. Suppose your diet provides an average of 2,300 kcal per day. How many hours per week would you have to walk to burn off the extra calories? Swim? Run?

100 kcal per day is 700 kcal per week. According to Figure 6.4, walking 3 mph would require 700/245 = about 2.8 hours; swimming, 1.7 hours; running 0.7 hours.

Also embedded in the membrane are multiple copies of an enzyme complex called __________, which synthesizes ATP.

ATP synthase

Explain how your body can convert excess carbohydrates in the diet to fats. Can excess carbohydrates be converted to protein? What else must be supplied?

As carbohydrates are broken down in glycolysis and the oxidation of pyruvate, glycerol can be made from G3P and fatty acids can be made from acetyl CoA. Amino groups, containing N atoms, must be supplied to various intermediates of glycolysis and the citric acid cycle to produce amino acids.

__________ occurs in the cytosol of the cell.

Glycolysis

Which of the three stages of cellular respiration is considered the most ancient? Explain your answer.

Glycolysis is considered the most ancient because it occurs in all living cells and doesn't require oxygen or membrane-enclosed organelles.

For a short time in the 1930s, some physicians prescribed how doses of a compound called dinitrophenol (DNP) to help patients lose weight. This unsafe method was abandoned after some patients died. DNP uncouples the chemiosmotic machinery by making the inner mitochondrial membrane leaky to H+. Explain how this drug could cause profuse sweating, weight loss, and possibly death.

In a person treated with uncoupling agents like DNP, the proton gradient established during electron transport is no longer tied to ATP synthesis. As a result, oxidation of glucose during cellular respiration yields very little ATP, since ATP is normally produced as H+ ions flow back through ATP synthase in the inner mitochondrial membrane. Without large amounts of ATP available, biosynthesis cannot take place and new organic molecules cannot be synthesized. Low ATP levels would signal the body to continue breaking down its own molecules and feeding them into the cellular respiration pathway, leading to excessive weight loss and severe overheating, sweating, and dehydration. One or a combination of these factors can cause death.

Compare and contrast fermentation as it occurs in your muscle cells and in yeast cells.

In lactic acid fermentation (in muscle cells), pyruvate is reduced by NADH to form lactate, and NAD+ is recycled. In alcohol fermentation, pyruvate is broken down to CO2 and ethanol as NADH is oxidized to NAD+. Both types of fermentation allow glycolysis to continue to produce 2 ATP per glucose by recycling NAD+.

An important player in the process of oxidizing glucose is a coenzyme called __________, which accepts electrons and becomes reduced to NADH.

NAD+

Your body makes NAD+ and FAD from two B vitamins, niacin and riboflavin. The Recommended Dietary Allowance for niacin is 20 mg and for riboflavin, 1.7 mg. These amounts are thousand of times less than the amount of glucose your body needs each day to fuel its energy needs. Why is the daily requirement for these vitamins so small?

NAD+ and FAD are coenzymes that are not used up during the oxidation of glucose. NAD+ and FAD are recycled when NADH and FADH2 pass the electrons they are carrying to the electron transport chain. We need a small additional to replace those that are damaged.

__________ involves electron transport and a process known as chemiosmosis.

Oxidative phosphorylation

Explain how the mechanism of brown fat metabolism is similar to the effect that the drug DNP described above has on mitochondria. Pharmaceutical companies may start targeting brown fat for weight loss drugs. How might such drugs help patients lose weight? What dangers might such drugs pose?

The mitochondria of brown fat cell have protein channels that make the inner mitochondrial membrane leaky to H+ ions, producing the same effect that the drug DNP has on mitochondria. When these channels are activated, brown fat burns fuel without producing ATP. Drugs that could activate brown fat would help a patient burn more calories. Thus, excess calories form the diet would not be converted to fat, and fat stores of the body could be reduced. If these drugs somehow affected the mitochondria of all body cells, however, the results could be as disastrous as they were with DNP.

Several studies have found a correlation between the activity levels of brown fat tissue in research participants following exposure to cold and their percentage of body fat. Devise a graph that would present the results from such a study, labeling the axes and drawing a line to show whether the results show a positive or negative correlation between the variables. Propose two hypotheses that could explain these results.

The percentage of body fat is the independent variable and is plotted on the x axis. The activity brown fat is the dependent variable, and it is plotted on the y axis. Your graph should show a negative correlation between body fat percentage and activity of brown fat (the data points are higher for lower body fat percentage and decrease as the body fat percentage increases). One hypothesis is that thin individuals have more active brown fat and thus burn more calories, which contributes to their thinness (lower percentage of body fat). A second hypothesis is that the higher percentage of body fat insulated the bodies of the more overweight subjects, thus their brown fat did not have to be as active to maintain their body temperatures when exposed to cold.

Recent data suggests that heat-generating born fat is most active in ________________. a. babies b. lean people exposed to cold temperatures c. obese people exposed to cold temperatures. d. All individuals exposed to cold temperature

a and b: babies and lean people exposed to cold temperatures

Which of the following is a true distinction between cellular respiration and fermentation? a. NADH is oxidized by passing electrons to the electron transport chain in respiration only. b. Only respiration oxidizes glucose. c. Substrate-level phosphorylation is unique to fermentation; cellular respiration uses oxidative phosphorylation d. Fermentation is the metabolic pathway found in prokaryotes; cellular respiration is unique to eukaryotes.

a. NADH is oxidized by passing electrons to the electron transport chain in respiration only.

In the citric acid cycle, an enzyme oxidizes malate to oxaloacetate, with the production of NADH and the release of H+. You are studying this reaction using a suspension of bean cell mitochondria and a blue dye that loses its color as it takes up H+. You know that the higher the concentration of malate, the more rapid the decolorization of the dye. You set up reaction mixtures with mitochondria, dye, and three different concentrations of malate (0.1 mg/L, 0.2 mg/L, and 0.3 mg/L). Which of the following graphs represents the results you would expect, and why?

a. No, this shows the blue color getting more intense. The reaction decolorizes the blue dye. b. No, this shows the dye being decolorized, but it also shows the three mixtures with different initial color intensities. The intensities should have started out the same, since all mixtures used the same concentration of dye. c. Correct. The mixtures all start out the same, and then the ones with more malate (reactant) decolorize faster.

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 _________. a. build amino acids, fats, and sugars b. generate the ADP that is used to power biosynthetic pathways c. provide virtually all the heat needed to maintain body temperature d. create energy sources, such as glucose or amino acids, that are recycled back through respiration, thus allowing a continual source of ATP with relatively little food intake

a. build amino acids, fats, and sugars

Lungs are to breathing as ________ are to cellular respiration. a. mitochondria b. alveoli c. chloroplasts d. bronchi

a. mitochondria

A compound called coenzyme A, derived from a B vitamin, joins with the two-carbon group to form a molecule called acetyl coenzyme A, abbreviated __________.

acetyl CoA

For thousands of years, people have used __________ in brewing, winemaking, and baking.

alcohol fermentation

We inhale O2 and we exhale CO2. Carbon dioxide is produced _________. a. when oxygen acquires electrons and protons at the end of the electron transport chain b. In the reaction that creates acetyl CoA (coenzyme A) from pyruvate c. during the electron transfer steps of oxidative phosphorylation d. during the formation of pyruvate

b. In the reaction that creates acetyl CoA (coenzyme A) from pyruvate

During fermentation, ___________ that was produced during glycolysis is converted back to __________. a. ATP; ADP b. NADH; NAD+ c. pyruvate; CO2; pyruvate d. NAD+; NADH

b. NADH; NAD+

In cellular respiration, glucose ________ electrons, whereas ________ electrons. a. loses ... water gains b. loses ... oxygen gains c. gains ... oxygen loses d. gains ... water loses

b. loses ... oxygen gains

Some human cells, such as nerve cells, are restricted to aerobic respiration to recycle NADH and FADH2. If these cells are deprived of oxygen, then __________. a. proton gradient formation would continue, but ATP synthase function would stop b. oxidative phosphorylation would come to a halt because there wouldn't be any oxygen to "pull" the electrons down the transport chain c. ATP production would continue because the cell would perform fermentation d. glycolysis could still continue indefinitely

b. oxidative phosphorylation would come to a halt because there wouldn't be any oxygen to "pull" the electrons down the transport chain

In which of the following is the first molecule becoming reduced to the second molecule? a. pyruvate --> acetyl CoA b. pyruvate --> lactate c. glucose --> pyruvate d. NADH + H+ --> NAD+ + 2H

b. pyruvate --> lactate

Glycolysis is the only stage of cellular respiration that _______. a. does not release carbon dioxide as a by-product b. requires ATP to make ATP c. does not require ATP to make ATP d. requires oxygen to function

b. requires ATP to make ATP

Which of the following is the most immediate source of energy for making most of the ATP in your cells? a. the transfer of phosphate from intermediate substrates to ADP b. the movement of H+ across a membrane down its concentration gradient c. the splitting of glucose into two molecules of pyruvate d. electrons moving through the electron transport chain

b. the movement of H+ across a membrane down its concentration gradient

The poison cyanide binds to an electron within the electron transport chain and blocks the movement of electrons. When this happens, glycolysis and the citric acid cycle soon grind to halt as well. Why do you think theses other two stages of cellular respiration stop? (Explain your answer.) a. They run out of ATP. b. Unused O2 interferes with cellular respiration. c. They run out of NAD+ and FAD. d. Electrons are no longer available.

c. They run out of NAD+ and FAD.

Each turn of the citric acid cycle generates one ATP and ___________ additional energy-rich molecules: _________________________. a. three; 2 NADH and 1 FADH2 b. two; 1 NADH and 1 FADH2 c. four; 3 NADH and 1 FADH2 d. 2 NADH and 2 FADH2

c. four; 3 NADH and 1 FADH2

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 ________. a. ATP and heat b. potential energy and heat c. kinetic energy and heat d. thermal energy and heat

c. kinetic energy and heat

A molecule that functions as the electron donor in a redox reaction ___________. a. gains electrons and becomes oxidized b. gains electrons and becomes reduced c. loses electrons and becomes oxidized d. loses electrons and becomes reduced

c. loses electrons and becomes oxidized

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 theses enzymes? a. mitochondrial inner membrane b. plasma membrane c. mitochondrial matrix d. cytoplasm

c. mitochondrial matrix

In oxidative phosphorylation, electrons are passed down from one electron carrier to another. The energy released is used to ___________. a. synthesize carbon dioxide b. generate large amounts of NADH and FADH2 c. pump protons (H+) across the mitochondrial membrane d. form ATP during glycolysis

c. pump protons (H+) across the mitochondrial membrane

Fat is the most efficient molecule for long term energy storage even compared to carbohydrates because _________. a. fats can directly enter the electron transport chain, the phase of respiration that produces the most ATP b. compared to carbohydrates, fat produces were toxic by-products when it is metabolized c. with their numerous hydrogen atoms, fats provide an abundant source of high-energy electrons d. when compacted, fat occupies less volume than an equivalent amount of carbohydrate

c. with their numerous hydrogen atoms, fats provide an abundant source of high-energy electrons

In __________, O2 is consumed as sugar is broken down to CO2 and H2O; the cell captures energy released in ATP.

cellular respiration

In __________, the potential energy of this concentration gradient is used to make ATP.

chemiosmosis

Pyruvate oxidation and the __________ take place within the mitochondria.

citric acid cycle

A biochemist wanted to study how various substances were used in cellular respiration. In one experiment, she allowed a mouse to breathe air containing O2 "labeled by a particular isotope. In the mouse, the labeled oxygen first showed up in a. ATP b. NADH c. CO2 d. H2O

d. H2O

Given the relatively modest number of calories burned by anything but the most vigorous activities, why can people consume over 2,000 kilocalories a day, yet maintain a healthy body weight? a. People really should exercise vigorously for one to two hours per day. b. They can't and this has led to a problem of obesity in the United States. c. Not all calories are created equal, so a person who consumes 2,000 kilocalories of sugar- and fat-laden processed food will gain weight, whereas a person who consumes 2,000 calories of non processed, low-carbohydrate food will not. d. Most of the energy consumed in food is spent maintaining the body's functions, so only a fraction of food energy needs to be burned in exercise.

d. Most of the energy consumed in food is spent maintaining the body's functions, so only a fraction of food energy needs to be burned in exercise.

In glycolysis, __________________ is oxidized and __________________ is reduced. a. NAD+ ... glucose b. glucose ... oxygen c. ATP ... ADP d. glucose ... NAD+

d. glucose ... NAD+

Sunlight is essential for the varied life on Earth. Sunlight provides energy to photosynthetic organisms by providing _________. a. heat to leaves, which is used to synthesize chloroplasts b. heat to leaves, which is converted to useful energy for work c. the energy required to drive cellular respiration d. the energy necessary to power the rearrangement of chemical bonds in H2O and CO2

d. the energy necessary to power the rearrangement of chemical bonds in H2O and CO2

Oxidative phosphorylation could not occur without glycolysis and the citric acid cycle, because __________. a. these two stages provide the water that is split during oxidative phosphorylation b. the electron transport chain requires the ATP produced during the first two stages c. these two stages provide the oxygen used as the final electron acceptor d. these two stages supply the electrons needed for the electron transport chain

d. these two stages supply the electrons needed for the electron transport chain

Compounds that form between the initial reactant, glucose, and the final product, pyruvate, are known as __________.

intermediates

The energy units are __________, a measure of the quantity of heat required to raise the temperature of 1 kilogram (kg) of water by 1°C.

kilocalories (kcal)

One common type of fermentation is called __________.

lactic acid fermentation

In a redox reaction, the loss of electrons from one substance is called __________, and the addition of electrons to another substance is called __________.

oxidation; reduction

The movement of one molecule to another is an oxidation-reduction reaction, or __________, for short.

redox reaction

Figure 6.7B illustrates how ATP is formed in glycolysis by the process called __________.

substrate-level phosphorylation

ATP synthase enzymes are found in the prokaryotic plasma membrane and in the inner membrane of a mitochondrion. What does this suggest about the evolutionary relationship of this eukaryotic organelle to prokaryotes?

the presence of ATP synthase enzymes in prokaryotic plasma membranes and the inner membrane of mitochondria provides support for the theory of endosymbiosis - that mitochondria evolved from an engulfed prokaryote that used aerobic respiration.