Nearly all of the energy used by living cells comes from the energy in the bonds of the sugar glucose. As glycolysis takes place in the cytoplasm of both prokaryotic and eukaryotic cells, it is probably one of the earlier metabolic pathways to evolve since it is used by nearly all the organisms on Earth. As discussed, why are coupled reactions important in the process of glycolysis?

Nearly all of the energy used by living cells comes from the energy in the bonds of the sugar glucose. As glycolysis takes place in the cytoplasm of both prokaryotic and eukaryotic cells, it is probably one of the earlier metabolic pathways to evolve since it is used by nearly all the organisms on Earth. As discussed, why are coupled reactions important in the process of glycolysis?

Concepts of Biology

1st Edition

ISBN:9781938168116

Author:Samantha Fowler, Rebecca Roush, James Wise

Publisher:Samantha Fowler, Rebecca Roush, James Wise

Chapter4: How Cells Obtain Energy

Section: Chapter Questions

Problem 17CTQ: Both prokaryotic and eukaryotic organisms carry out some form of glycolysis. How does ha fact...

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Both prokaryotic and eukaryotic organisms carry out some form of glycolysis. How does that fact support or not support the assertion that glycolysis is one of the oldest metabolic pathways?
While the conversion of glucose (Glc) to pyrucate (Pyr) is shared across all domains of life, the route to get there can differ dramatically. In some Archaea, for example, some of the key steps in glycolysis differ. One example of this is the conversion of glyceraldehyde 3-phosphate (GAP) to 3-phosphoglycerate (3PG). Instead of the two-step process catalyzed by GAPDH and PGK: GAPDH GAP + Pi + NAD+ -----> BGP + NADH PGK BGP + ADP <-----> 3PG + ATP The archaeal pathway utilizes the enzyme non-phosporylating glyceraldehyde-3-phosphate dehydrogenase (GAPN) to catalyze the metabolically irreversible step shown below: GAPN GAP + NADP+ ---> BGP + NADPH In bacteria and eukaryotes, GAPDH/PGK are not regulated via allosteric activation or inhibition. Do you imagine this is the same for GAPN? Why or why not?
While the conversion of glucose (Glc) to pyrucate (Pyr) is shared across all domains of life, the route to get there can differ dramatically. In some Archaea, for example, some of the key steps in glycolysis differ. One example of this is the conversion of glyceraldehyde 3-phosphate (GAP) to 3-phosphoglycerate (3PG). Instead of the two-step process catalyzed by GAPDH and PGK: GAPDH GAP + Pi + NAD+ -----> BGP + NADH PGK BGP + ADP <-----> 3PG + ATP The archaeal pathway utilizes the enzyme non-phosporylating glyceraldehyde-3-phosphate dehydrogenase (GAPN) to catalyze the metabolically irreversible step shown below: GAPN GAP + NADP+ ---> BGP + NADPH In terms of the ΔGrxn, why is the GAPDH+PGK process reversible but the GAPN process is not?
In living cells, true equilibrium is dangerous because if the rate of a forward reaction is equal to the rate of the reverse reaction, a wasteful cycle is produced during which the cell gains no new nutrients. In this situation, the cell will eventually die. Therefore, organisms have many ways of ensuring that reactions move only in the forward direction. One of these means is control over reactant concentration. The Citric Acid Cycle is a series of reactions that occur in eukaryotic cell mitochondria which are essential for providing energy to living cells. During one of these reactions, a molecule known as oxaloacetate is combined with acetyl coenzyme-A to produce citrate. Normally, the concentration of oxaloacetate in mitochondria is very low. If the cell is in need of more energy and the concentration of oxaloacetate increases, what will happen to the direction and of this reaction? How do you suppose this affects the overall amount of energy product produced?
Cellular respiration is a metabolic process that breaks down glucose to produce adenosine triphosphate (ATP). Oxygen is an essential molecule to efficiently divert the glucose into an energy-rich molecules needed to sustain activities of the cell. Hence, carbon dioxide and water are the end-products of cellular respiration. The overall process can be refined into three main metabolic stages namely (1) glycolysis, (2) tricarboxylic acid cycle (TCA cycle), and (3) oxidative phosphorylation. In plant cells, the enzymes that catalyze the individual steps involved in respiration and energy conservation are located in highly organized compartment called mitochondrion. In this laboratory activity, you will use the germinated mung beans (Vigna radiata) to demonstrate what happens to the stored sugar in the seed upon its utilization during cellular respiration. At the end of the experiment, you are expected to identify what are the different factors that affect cellular respiration.
The energy for the production of ATP comes from the breakdown of a glucose molecule via many enzyme-mediated chemical reactions occurring at several distinct stages of cellular respiration. During this time, the chemical energy stored in glucose is continually trans- ferred across these reactions. Which of the following describes the form in which most of the energy from the glucose molecule is stored just before the oxidative phosphorylation stage in aerobic cellular respiration? A B с D acetyl CoA FADH 2 NADH pyruvate
How much ATP is made available to the cell from a single glucose molecule by the operation of (1) glycolysis, (2) the formation of acetyl CoA, (3) the citric acid cycle, and (4) the electron transport chain and chemiosmosis?Where does each of these processes take place in a eukaryotic cell?
a) What carbon-containing molecule exits the citric acid cycle? Why doesn’t your body capture the carbon-containing molecule you identified in part (a) and use that molecule to build new sugars and fats? Explain your answer. You have just created a new enzyme that will make the citric acid cycle more efficient! Instead of the citric acid cycle taking 8 steps, all of the bonds between the carbon atoms will be broken in only one step! Is this a good idea? Explain your answer.
Which statement best describes the reason why some of the reactions of glycolysis cannot be run in reverse in gluconeogenesis? 1) The last reactions occur in mitochondria and reactions there can never be reversed. 2) Glycolysis includes isomerization reactions and these can never be reversed. 3) There are some allaşteric enzymes and allosteric enzymes can never be reversed. 4) Some reactions have such large negative free energy changes that they can never be reversed under cellular conditions. O
Medical researchers are studying a patient with the newly discovered u LEKS metabolic syndrome, in which a genetic mutaton prevents NADH produced in the cytosol from being reoxidized by the electron transport chain. Suppose the following nutrient molecule is digested and metabolized by this patient under anaerobic conditions, e.g. during a sudden intense exertion: de HO-CH: -OH Он н. HO H OH How many ATP molecules will uttimately be produced by the catabolism of this molecule? Note: you can ussume the catabohism is as complete as it can be under the conditions given above. How many molecules of pyruvate will be produced during dycalysist How many maleoules of lactate will be produced
In the living cell, free energy made from one reaction can be used to drive another in an energetically unfavorable direction, provided the two reactions have a common intermediate (this is termed the principle of common intermediates). Example: In glycolysis, glucose is converted into pyruvate; in gluconeogenesis, pyruvate is converted into glucose. However, the actual AG for the formation of pyruvate from glucose is about -84 kJ/mol under typical cellular conditions. Most of the decrease in free energy in glycolysis takes place in three essentially irreversible steps catalyzed by, hexokinase, pyruvate kinase and phosphofructokinase. Using this example, (i) From gluconeogenesis, identify enzymes/steps that catalyze reactions that oppose/ bypass the irreversible steps of glycolysis (ii) Use one of the 3 opposing reactions (in glycolysis and gluconeogenesis) to demonstrate the PRINCIPLE OF COMMON INTERMEDIATES
Some anaerobic bacteria use alternative pathways for glucose catabolism that convert glucose to acetate rather than to pyruvate. Shown below is one possible metabolic pathway. The first part of this pathway (glucose to fructose-1,6-bisphosphate) is identical to the glycolytic pathway. In the second part of the alternative pathway, Enzymes 1–6 all have mechanisms/ activities analogous t enzymes in glycolysis. Note that there are two C¬C bond cleavage reactions in this new pathway: A → B + C (Enzyme 1) and C → B + D. All the steps where ATP is consumed or generated have been shown; however, the addition or loss of NAD+/NADH, Pi , H2O, or H+ has not been shown explicitly. Draw the structures for the intermediates B, F, G, H, and I, and include other reaction participants as needed.