Question 1

The oxidative reactions of cellular respiration were the focus of intense study in the 1930s.These reactions are represented in a linear pathway, as they were thought to occur.Each product is designated as a lettered compound (A through H) in Figure 13-16. $\begin{array}{ccccccccccc}
A&\longrightarrow&B&\longrightarrow&C&\longrightarrow&D&\longrightarrow&E&\longrightarrow&F&\longrightarrow&G&\longrightarrow&H\
&\text { citrate }&&\text { isocitrate }&&\alpha \text {-ketoglutarate }&&\text { succinyl CoA }&&\text { succinate }&&\text { fumarate }&&\text { malate }\
&\text { oxaloacetate }\
\end{array}$
 
Figure 13-16
A.What was the first observation that Krebs made when he added malonic acid to the minced muscle samples, and what was his conclusion about how and where it was acting in the reactions he was studying?
B.What happens when the malonate block is introduced and subsequently compound A is added in excess? What is the result if compound G is added after the block, instead of A? How did Krebs attempt to reconcile these two results?
C.What additional observation led Krebs to hypothesize that what was previously thought to be a linear sequence of reactions is actually a cyclic sequence of reactions? How did this idea further explain the earliest observations that the addition of any single compound in the pathway greatly increases oxygen uptake by the muscle tissue?

Accepted Answer

The answer of The oxidative reactions of cellular respiration were...

Question 2

Although the outer mitochondrial membrane is permeable to all small molecules, the inner mitochondrial membrane is essentially impermeable in the absence of specific transport proteins.Consider this information and what you have learned about the citric acid cycle to address the following questions.
A.The ATP generated by oxidative respiration is used throughout the cell.The majority of ATP production occurs in the mitochondrial matrix.How do you think ATP is made accessible to enzymes in the cytosol and other organelles?
B.If the inner mitochondrial membrane were rendered as permeable as the outer membrane, how would that affect oxidative phosphorylation? Which specific processes would stop and which remain?
C.Present two types of benefits derived from separating the reactions of glycolysis in the cytosol from those that occur during the citric acid cycle in the mitochondrion.

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The answer of Although the outer mitochondrial membrane is permeable...

Question 3

Glycolysis and the citric acid cycle comprise two different sets of oxidation reactions.The reaction sequence for glycolysis is linear, whereas the reaction sequence for the citric acid cycle forms a circle.How does this difference in the arrangement of reactions influence the rate of these processes when an excess amount of a single intermediate is added?

Accepted Answer

The answer of Glycolysis and the citric acid cycle comprise...

Question 4

In step 7 of the citric acid cycle, fumarase catalyzes the addition of a water molecule to a carbon-carbon double bond (see Panel 13-2).Can this be considered an oxidation reaction? Explain your answer.

Accepted Answer

The answer of In step 7 of the citric acid...

Question 5

For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below.Not all words or phrases will be used; each word or phrase should be used only once. $\begin{array}{lll} \text { amino acids } & \text { galactose } & \text { nucleotides } \ \text { carbon fixation } & \text { glucose } & \text { oxidative phosphorylation } \ \text { citric acid cycle } & \text { glycogen } & \text { pyruvate } \ \text { fatty acid } & \text { insulin } & \text { starch } \ \text { fermentation } & \text { lactate } & \text { triacylglycerol } \end{array}$ A carbon atom in a CO₂ molecule in the atmosphere eventually becomes a part of one of the enzymes that catalyzes glycolysis in one of your cells.The CO₂ first enters a cell in a corn leaf, where photosynthesis fixes the carbon to make it part of a sugar molecule; this travels from the leaf to an ear of corn, where it is stored as part of a polysaccharide __________ molecule in the corn seed.You then eat a corn chip made from the corn seed.You digest the corn seed, and the free __________ travels in your bloodstream, eventually being taken up by a liver cell and stored as __________.When required, this storage molecule breaks down into glucose 1-phosphate, which enters the glycolytic pathway.Glycolysis produces __________, which is converted into acetyl CoA, which enters the __________.Several intermediates in this process can provide the carbon skeleton for the production of __________, which are then incorporated into the enzymes that catalyze steps in glycolysis.

Accepted Answer

The answer of For each of the following sentences, fill...

Question 6

Match between columns Premises: Amino acids can be transported into the mitochondria and converted into acetyl CoA.
Anaerobic respiration is not the same as fermentation, as only the former requires an electron-transport chain.
When subjected to anaerobic conditions, glycolysis in mammalian cells continues and causes a buildup of pyruvate in the cytosol.
The pyruvate dehydrogenase complex catalyzes three different, but linked, enzymatic reactions.
During glycolysis, glucose molecules are broken down to yield CO₂ and H₂O. The cleavage of fructose 1,6-bisphosphate yields two molecules of glyceraldehyde 3-phosphate.

Accepted Answer

The Answer of False and True is...

Question 7

Match between columns Premises: With respect to the amount of energy stored in molecules of the body, 6 g of glycogen is the equivalent of 1 g of fat.
Glycogen phosphorylase cleaves glucose monomers from the glycogen polymer, phosphorylating them at the same time so that they can be fed unchanged into the glycolytic pathway.
The proteins of the electron-transport chain remove a pair of high-energy electrons from the cofactors NADH and FADH₂, after which the electrons move across the inner mitochondrial membrane to maintain the voltage gradient.
Gluconeogenesis is a linear reaction pathway that the cell employs to generate glucose from pyruvate and is exactly the reverse of the reactions in the glycolytic pathway.

Accepted Answer

The Answer of True and False is...

Question 8

In the reaction cycle involved in the oxidation of pyruvate, what are the advantages of having three enzyme activities contained in a single large complex instead of having three smaller and physically independent enzymes?

Accepted Answer

The answer of In the reaction cycle involved in the...

Question 9

For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below.Not all words or phrases will be used; each word or phrase may be used more than once.
$\begin{array}{lllll}
\text { ADP } & \mathrm{FADH}_{2} & \mathrm{H}^{+} & \text {moderately } & \text { protons } \
\text { ATP } & \text { favorable } & \text { higher } & \mathrm{NADH} & \text { severely } \
\text { cytosol } & \text { glucose } & \text { lower } & \mathrm{NAD}^{+} & \text {slightly } \
\text { electrons } & \text { GTP } & \text { matrix } & \mathrm{P}_{i} & \text { unfavorable }
\end{array}$

High-energy electrons are transferred through a series of molecules, and the energy released during these transfers is used to generate a gradient of __________, or __________.Because their concentration is __________ outside than inside the mitochondria, the flow of __________, or __________, down the concentration gradient is energetically very __________ and can thus be coupled to the production of ATP from ADP.Thus, oxidative phosphorylation refers to the oxidation of __________ and __________ molecules and the phosphorylation of __________.Without this process, the yield of ATP from each glucose molecule would be __________ decreased.

Accepted Answer

The answer of For each of the following sentences, fill...

Question 10

Do you expect the cell to produce more ATP from one glucose molecule or from one fatty acid molecule? Explain your answer.

Accepted Answer

The answer of Do you expect the cell to produce...

Question 11

You are stranded on an island with no way to communicate or signal for help.Your only hope is that somebody has tracked your last known location and will begin a search from there.Nevertheless, it will be a while before you have a chance of seeing another person.You have found a fresh stream of water at the center of the island, but other than green leafy plants, food options appear nonexistent.
A.What substances are used as energy stores within your body? In which organs?
B.Which will be used first in the absence of ingesting external sources of energy? How long will this source last?
C.What other substance will your body then turn to? On average, how long before you run out of that fuel source? Explain why this second fuel source is a better choice than the first-used source as your long-term energy store.
D.What enzyme is required for the breakdown and usage of the energy source you listed in part B? If you are a person with a deficiency in that enzyme, how does this affect your other estimates?

Accepted Answer

The answer of You are stranded on an island with...

Quiz 13: How Cells Obtain Energy From Food

In step 7 of the citric acid cycle, fumarase catalyzes the addition of a water molecule to a carbon-carbon double bond (see Panel 13-2).Can this be considered an oxidation reaction? Explain your answer.

Indicate whether the following statements are TRUE or FALSE. If a statement is false, explain why it is false.

Indicate whether the following statements are TRUE or FALSE.If a statement is false, explain why it is false

In the reaction cycle involved in the oxidation of pyruvate, what are the advantages of having three enzyme activities contained in a single large complex instead of having three smaller and physically independent enzymes?

Do you expect the cell to produce more ATP from one glucose molecule or from one fatty acid molecule? Explain your answer.