Why does krebs cycle occur in the mitochondrial matrix

Glycolysis is a series of chemical reactions performed by enzymes in the cytosol of all cells. They convert the glucose, which is a 6 carbon sugar, into two molecules of pyruvate, which has 3 carbons. In the process, two molecues of ATP are made, as are a couple of NADH molecules, which are reductants and can donate electrons to various reactions in the cytosol.

Glycolysis requires no oxygen. It is an anaerobic type of respiration performed by all cells, including anaerobic cells that are killed by oxygen. For these reasons, glycolysis is believed to be one of the first types of cell respiration and a very ancient process, billions of years old.

In the present, many cells add a step to glycolysis if oxygen is not available. In the case of yeast cells, this extra step is the conversion of pyruvate to ethanol alcohol and carbon dioxide CO 2. This extra step is called "fermentation". It is the process by which baking yeasts cause bread to rise and brewing yeasts add alcohol to beer and wine. Your muscle cells also add a fermentation step to glycolysis when they don't have enough oxygen. Like the conversion of pyruvate to acetyl CoA, the citric acid cycle in eukaryotic cells takes place in the matrix of the mitochondria.

Unlike glycolysis, the citric acid cycle is a closed loop: The last part of the pathway regenerates the compound used in the first step. Part of this is considered an aerobic pathway oxygen-requiring because the NADH and FADH 2 produced must transfer their electrons to the next pathway in the system, which will use oxygen. If oxygen is not present, this transfer does not occur. Two carbon atoms come into the citric acid cycle from each acetyl group. Two carbon dioxide molecules are released on each turn of the cycle; however, these do not contain the same carbon atoms contributed by the acetyl group on that turn of the pathway.

The two acetyl-carbon atoms will eventually be released on later turns of the cycle; in this way, all six carbon atoms from the original glucose molecule will be eventually released as carbon dioxide. It takes two turns of the cycle to process the equivalent of one glucose molecule. These high-energy carriers will connect with the last portion of aerobic respiration to produce ATP molecules.

One ATP or an equivalent is also made in each cycle. Several of the intermediate compounds in the citric acid cycle can be used in synthesizing non-essential amino acids; therefore, the cycle is both anabolic and catabolic. You have just read about two pathways in glucose catabolism—glycolysis and the citric acid cycle—that generate ATP. Most of the ATP generated during the aerobic catabolism of glucose, however, is not generated directly from these pathways.

Rather, it derives from a process that begins with passing electrons through a series of chemical reactions to a final electron acceptor, oxygen. These reactions take place in specialized protein complexes located in the inner membrane of the mitochondria of eukaryotic organisms and on the inner part of the cell membrane of prokaryotic organisms.

The energy of the electrons is harvested and used to generate a electrochemical gradient across the inner mitochondrial membrane. The potential energy of this gradient is used to generate ATP. The entirety of this process is called oxidative phosphorylation. The electron transport chain Figure 4.

Nuclear localization sequence 4. Amino terminal signal sequence of hydrophobic amino acids b. Nuclear localization sequence c. Ribosome d. Glycoprotein 5. Microtubules b. Lamina c. Actin d. Dynein 6. Actin and microtubules c. Water d. ATP 7. Oxidize very long chains of lipids b. Contain digestive enzymes that can degrade biochemical molecules c.

Production of ATP by oxidative phosphorylation d. Detoxification and lipid synthesis 8. ER; chloroplast b. Chloroplast; lysosome c. Mitochondria; nucleus d. Chapter 9: Cellular Respiration Chapter 8 material not covered in lecture, not on test 1.

Anabolism is: a Synthesizing new cellular molecules b Breaking down molecules c Oxidizing glucose d None of the above 2. The conversion of pyruvate to acetyl CoA is the junction between: a Krebs cycle and electron transport b Glycolysis and electron transport c Photosynthesis and respiration d Glycolysis and Krebs cycle 7. Chapter Photosynthesis 1. Name the three components of a photosystem a glycolysis , Kreb cycle, electron transport chain b photosystem II, cytochrome complex, photosystem I c light-independent reaction, Calvin cycle, dark cycle d antenna complex, reaction center, primary electron acceptor 5.

As Oxygen levels rise, cell undergoes this wasteful process, which generates no ATP a Glycolysis b Fermentation c C4 metabolism d photorespiration 8. Chapter Mitosis 1. Step 3. The enzyme-bound acetyl group is transferred to CoA, producing a molecule of acetyl CoA. This molecule of acetyl CoA is then further converted to be used in the next pathway of metabolism, the citric acid cycle.

The citric acid cycle is a key component of the metabolic pathway by which all aerobic organisms generate energy. The citric acid cycle, shown in —also known as the tricarboxylic acid cycle TCA cycle or the Krebs cycle—is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidation of acetate—derived from carbohydrates, fats, and proteins—into carbon dioxide.

The cycle provides precursors including certain amino acids as well as the reducing agent NADH that is used in numerous biochemical reactions. Its central importance to many biochemical pathways suggests that it was one of the earliest established components of cellular metabolism; it may have originated abiogenically.

The Citric Acid Cycle : The citric acid cycle, or Krebs cycle, is a series of chemical reactions used by all aerobic organisms to generate energy through the oxidization of acetate—derived from carbohydrates, fats, and proteins—into carbon dioxide.

In addition, the cycle provides precursors including certain amino acids as well as the reducing agent NADH that is used in numerous biochemical reactions. The name of this metabolic pathway is derived from citric acid, a type of tricarboxylic acid that is first consumed and then regenerated by this sequence of reactions to complete the cycle.

The net result of these two closely linked pathways is the oxidation of nutrients to produce usable energy in the form of ATP. Components of the TCA cycle were derived from anaerobic bacteria, and the TCA cycle itself may have evolved more than once. Theoretically there are several alternatives to the TCA cycle, however the TCA cycle appears to be the most efficient.

If several alternatives independently evolved, they all rapidly converged to the TCA cycle. Through the catabolism of sugars, fats, and proteins, a two carbon organic product acetate in the form of acetyl-CoA is produced. One of the primary sources of acetyl-CoA is sugars that are broken down by glycolysis to produce pyruvate that, in turn, is decarboxylated by the enzyme pyruvate dehydrogenase.

This generates acetyl-CoA according to the following reaction scheme:. Privacy Policy. Skip to main content. Microbial Metabolism. Search for:.