Describe the net reaction of glycolysis.
Key Terms
Which metabolic process immediately follows glycolysis in oxygen-poor conditions?
Fermentation This process takes place when O2 is too scarce to facilitate the entry of glycolytic products into the Krebs cycle.
Fermentation...
The conversion of pyruvate to lactic acid, often referred to simply as 'fermentation,' produces no ATP. However, it is still necessary in anaerobic conditions. What purpose does this process serve?
Fermentation regenerates NAD+ by oxidizing NADH and reducing pyruvate.
NAD+ is necessary for glycolysis, but cannot be regenerated by the ele...
Two glucose molecules undergo glycolysis, producing pyruvate. How many molecules of NADH will be produced simply from the decarboxylation of these pyruvate products?
4 NADH molecules
During glycolysis, the initial two glucose molecules will be converted into four molecules of pyruvate. For every molecule o...
Which metabolic process generates both NADH and FADH2?
The Krebs cycle produces the electron carriers NADH and FADH2, as well as an ATP equivalent (either ATP or GTP).
The Krebs cycle, also known ...
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| Term | Definition |
|---|---|
Describe the net reaction of glycolysis. | C6H12O6 + 2NAD+ + 2 Pi + 2 ADP ⇒ 2 pyruvate + 2 ATP + 2 NADH + 2 H2O + 2 H+ |
Which metabolic process immediately follows glycolysis in oxygen-poor conditions? | Fermentation This process takes place when O2 is too scarce to facilitate the entry of glycolytic products into the Krebs cycle. Fermentation can produce either ethanol or lactic acid, depending on the species. |
The conversion of pyruvate to lactic acid, often referred to simply as 'fermentation,' produces no ATP. However, it is still necessary in anaerobic conditions. What purpose does this process serve? | Fermentation regenerates NAD+ by oxidizing NADH and reducing pyruvate. NAD+ is necessary for glycolysis, but cannot be regenerated by the electron transport chain under anaerobic conditions. Fermentation serves to produce NAD+, reducing buildup of NADH and allowing glycolysis to continue. |
What are the substrates and products of pyruvate decarboxylation? | Pyruvate, a three-carbon molecule, is the substrate. CO2, NADH, and acetyl-CoA are the ultimate products. |
Two glucose molecules undergo glycolysis, producing pyruvate. How many molecules of NADH will be produced simply from the decarboxylation of these pyruvate products? | 4 NADH molecules During glycolysis, the initial two glucose molecules will be converted into four molecules of pyruvate. For every molecule of pyruvate that is decarboxylated by pyruvate dehydrogenase, one molecule of NADH is formed. |
Which metabolic process generates both NADH and FADH2? | The Krebs cycle produces the electron carriers NADH and FADH2, as well as an ATP equivalent (either ATP or GTP). The Krebs cycle, also known as the citric acid cycle, involves the cyclic transformation of organic molecules. It occurs in the mitochondrial matrix. |
Which metabolic process takes place along the inner mitochondrial membrane? | The electron transport chain (ETC) uses a series of complexes along the inner mitochondrial membrane. These molecules support a chain of oxidation-reduction reactions, ultimately resulting in the oxidization of NADH and FADH2 and the reduction of O2. The transport of electrons through the chain creates a proton gradient that provides the energy to convert ADP to ATP. |
Which metabolic process is facilitated by the proton gradient within the mitochondria? | ATP synthesis After establishment of the gradient, proton concentration in the intermembrane space is high. When possible, these protons will move down their gradient and reenter the matrix; this can only occur if they pass through ATP synthase, an enzyme. As this process occurs, ATP synthase uses this energy to convert ADP to ATP. |
Which of the following molecules are necessary substrates for the electron transport chain?
| NADH is a required substrate, and O2 must be present as the final electron acceptor in the chain. Glucose and pyruvate, though linked to NADH production, are not directly necessary for the electron transport chain. CO2 is a waste product of cellular respiration. |
Which of the following molecules are necessary substrates for fermentation?
|
Ethanol, lactate, and NAD+ are all products of fermentation. |
Which of the following molecules are products of glycolysis?
|
NADH, though not listed here, is another glycolytic product. Glucose and NAD+ are consumed in glycolysis, while O2 is not involved. Remember that glycolysis is an anaerobic process. |
Which of the following molecules are products of the Krebs cycle?
| The Krebs cycle produces NADH and FADH2, which are electron carriers that are later used. Acetyl-CoA and NAD+ are consumed in the Krebs cycle, while pyruvate is not directly involved. |
Which two processes of cellular metabolism take place in the cytoplasm? |
Note that fermentation only takes place in anaerobic conditions. All other processes take place in the mitochondria. |
Which two processes of cellular metabolism take place in the mitochondrial matrix? |
The electron transport chain is also a mitochondrial process, but occurs along the inner membrane, not within the matrix itself. |
Which enzymes are responsible for the metabolism of proteins? | Proteases | also called peptidases Proteins are cleaved into amino acids. Depending on their identity, these amino acids can be converted to acetyl-CoA, pyruvate, or other metabolic intermediates. |
What homeostatic change occurs in the blood when the cells are in oxygen debt? | Acidosis | or low pH This is the result of excess CO2 and the buildup of lactic acid in muscles during anaerobic respiration. Note that normal plasma pH is 7.4. |
The majority of glucose molecules enter the cell via which transport method? | facilitated diffusion This occurs with the assistance of a family of transport proteins. This process is promoted by high plasma glucose levels, which creates a concentration gradient that drives glucose into the cells. It is also promoted by the activity of insulin, which increases the number of glucose transporters on the membranes of certain cell types. |
Which reaction is the rate-limiting step of glycolysis? | The phosphorylation of fructose 6-phosphate. This reaction is catalyzed by the enzyme phosphofructokinase-1 (PFK-1). For this reason, PFK-1 is sometimes called the rate-limiting enzyme of glycolysis. |
Of AMP, ATP, and citrate, which is most likely to serve as an allosteric activator of PFK-1? | AMP The other two molecules are inhibitors. You can figure this out logically: "activate" means "stimulate." Glycolysis should be stimulated when available energy is low (to make more) and inhibited when it is high. High AMP concentrations imply that cellular ATP is low. |
What is the chemical formula of glucose? | C6H12O6 |