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In lactic acid fermentation, pyruvate is reduced to NADH, forming lactate as an end product, with no release of CO2.

Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt. Human muscle cells use lactic acid fermentation to generate ATP when O2 is scarce.

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In alcohol fermentation, pyruvate is converted to ethanol in two steps, with the first releasing CO2.

Alcohol fermentation by yeast is used in brewing, winemaking, and baking. 

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Two common types are alcohol fermentation and lactic acid fermentation. 

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The flow of protons back through membrane-bound ATP synthase by chemiosmosis generates ATP from ADP and inorganic phosphate.

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Electron transport chain reactions occur across the Christae of the mitochondria (inner membrane).

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The electron transport chain captures free energy from electrons in a series of coupled reactions that establish an electrochemical gradient across membranes

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its events take place within the mitochondrial matrix.

• it generates 1 ATP, 3 NADH, and 1 FADH2 per turn.

• Electrons that are extracted in the series of Krebs cycle reactions are carried by NADH and FADH2 to the electron transport chain.

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In the Krebs cycle, carbon dioxide is released from organic intermediations ATP is synthesized from ADP and inorganic phosphate

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The conversion of pyruvate to acetyl CoA is the junction between glycolysis (step 1) and the Krebs cycle (step 2).

• If oxygen is present, Pyruvate (3 C each) from glycolysis enters the mitochondrion.

• Using Coenzyme A, each pyruvate is converted into a molecule of Acetyl CoA (2 C each).

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The pyruvate produced during glycolysis is transported from the cytoplasm to the mitochondrion, where further oxidation occurs.

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2 ATPs are needed to produce 4 ATPs (energy investment and energy payoff phases), so there is a net production of 2 ATPs.

• A second product in glycolysis is 2 NADH, which results from the transfer of eand H+ to the coenzyme NAD+ .

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The first step is the phosphorylation of glucose (glucose molecule gains 2 inorganic phosphates) – this ACTIVATES the glucose to split.

• The second step is the splitting of glucose – breaking it down into (2) 3-carbon molecules called pyruvic acid. This process is achieved by stripping electrons and hydrogens from the unstable 3-C molecules (as well as the borrowed phosphates).

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Glycolysis is the first step in the breakdown of glucose to extract energy for cellular metabolism. Glycolysis consists of an energy-requiring phase followed by an energy-releasing phase.

Introduction

Suppose that we gave one molecule of glucose to you and one molecule of glucose to Lactobacillus acidophilus -the friendly bacterium that turns milk into yogurt. What would you and the bacterium do with your respective glucose molecules?

Overall, the metabolism of glucose in one of your cells would be pretty different from its metabolism in Lactobacillus-check out the fermentation article for more details. Yet, the first steps would be the same in both cases: both you and the bacterium would need to split the glucose molecule in two by putting it through glycolysis.

What is glycolysis?

In organisms that perform cellular respiration, glycolysis is the first stage of this process. However, glycolysis doesn't require oxygen, and many anaerobic organisms-organisms that do not use oxygen-also have this pathway.

Highlights of glycolysis

Glycolysis has ten steps, and depending on your interests-and the classes you're taking-you may want to know the details of all of them. However, you may also be looking for a greatest hits version of glycolysis, something that highlights the key steps and principles without tracing the fate of every single atom. Let's start with a simplified version of the pathway that does just that.

Glycolysis takes place in the cytosol of a cell, and it can be broken down into two main phases: the energy-requiring phase, above the dotted line in the image below, and the energy-releasing phase, below the dotted line.

Energy-requiring phase. In this phase, the starting molecule of glucose gets rearranged, and two phosphate groups are attached to it. The phosphate groups make the modified sugar-now called fructose-1,6-bisphosphate-unstable, allowing it to split in half and form two phosphate-bearing three-carbon sugars. Because the phosphates used in these steps come from , two molecules get used up.

The three-carbon sugars formed when the unstable sugar breaks down are different from each other. Only one-glyceraldehyde-3-phosphate-can enter the following step. However, the unfavorable sugar, , can be easily converted into the favorable one, so both finish the pathway in the end

Energy-releasing phase. In this phase, each three-carbon sugar is converted into another three-carbon molecule, pyruvate, through a series of reactions. In these reactions, two molecules and one molecule are made. Because this phase takes place twice, once for each of the two three-carbon sugars, it makes four and two overall.

Detailed steps: Energy-requiring phase

We've already seen what happens on a broad level during the energy-requiring phase of glycolysis. Two s are spent to form an unstable sugar with two phosphate groups, which then splits to form two three-carbon molecules that are isomers of each other.

Next, we'll look at the individual steps in greater detail. Each step is catalyzed by its own specific enzyme, whose name is indicated below the reaction arrow in the diagram below.

Step 2. Glucose-6-phosphate is converted into its isomer, fructose-6-phosphate.

Detailed steps: Energy-releasing phase

Here, we'll look in more detail at the reactions that lead to these products. The reactions shown below happen twice for each glucose molecule since a glucose splits into two three-carbon molecules, both of which will eventually proceed through the pathway.

Step 8. 3-phosphoglycerate is converted into its isomer, 2-phosphoglycerate.

What happens to pyruvate and ?

Fermentation is a primary metabolic strategy for lots of bacteria-including our friend from the introduction, Lactobacillus acidophilus. Even some cells in your body, such as red blood cells, rely on fermentation to make their .

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Glycolysis | Cellular respiration | Biology (article) | Khan Academy

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Learn for free about math, art, computer programming, economics, physics, chemistry, biology, medicine, finance, history, and more. Khan Academy is a nonprofit with the mission of providing a free, world-class education for anyone, anywhere.

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• Glycolysis occurs in the cytoplasm and has two major phases: an energy investment phase and an energy payoff phase.

• Glycolysis occurs WITH or WITHOUT oxygen

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Glycolysis harvests chemical energy by oxidizing glucose to two molecules of pyruvate – it is the first stage of cellular respiration.

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Aerobic respiration consumes organic molecules and O2 and yields ATP.

Anaerobic respiration is similar to aerobic respiration but consumes compounds other than O2.

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Fermentation produces organic molecules, including alcohol and lactic acid, and it occurs in the absence of oxygen.

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Three parts of Cellular Respiration:

Glycolysis: (breaks down glucose into two molecules of pyruvate) – occurs in cytosol

• The citric acid cycle (completes the breakdown of glucose) – occurs in mitochondrial matrix

• Electron Transport/Oxidative Phosphorylation (accounts for most of the ATP synthesis) – occurs across inner membrane of mitochondria

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organic compounds + oxygen -----> carbon dioxide + water + energy

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Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate (ATP).