Name: pyruvate pathways in fermentation
Uploaded: 2025-05-22T09:05:36.000Z
Duration: 1 min 20 s
Channel: JoVE

K12 Standards

Florida Department of Education

High School

Life Science

SC.912.L.18

SC.912.L.18.8

Fates of Pyruvate

يمكن أن يكون للبيروفات ، المنتج النهائي لتحلل السكر ، العديد من المصائر الأيضية اعتمادا على الظروف الفسيولوجية داخل الكائن الحي.
في ظل الظروف الهوائية ، يتم تحويل البيروفات إلى أسيتيل إنزيم أ ، والذي يتم توجيهه بعد ذلك من خلال دورة TCA وسلسلة نقل الإلكترون لإنتاج الطاقة في شكل ATP.
ولكن ، في ظل الظروف اللاهوائية ، لا تعمل سلسلة نقل الإلكترون ، كما هو موضح في الخميرة والبكتيريا اللاهوائية. لذلك ، يتم تخمير البيروفات إلى الإيثانول مع أكسدة NADH إلى NAD +. ثم يتم إعادة تدوير NAD + مرة أخرى إلى تحلل السكر.
في معظم الفقاريات ، تؤدي الظروف المؤقتة المنخفضة الأكسجين إلى شكل آخر من أشكال تخمير البيروفات ، حيث يتم تخميره إلى لاكتات ، مما ينتج عنه NAD +.
يساعد تجديد NAD + أثناء التخمير الخلايا على الاستمرار في إنتاج ATP حتى في ظروف الأكسجين المنخفض عن طريق تحلل السكر.
أثناء انخفاض مستويات الجلوكوز في الدم ، يمكن أيضا تحويل البيروفات مرة أخرى إلى 6-فوسفات الجلوكوز عن طريق عملية تسمى استحداث الجلوكوز. ثم يتم تحويل الجلوكوز 6-فوسفات إلى جلوكوز ، مما يعيد مستوى الجلوكوز في الدم.

مصير البيروفات

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البيروفات هو المنتج النهائي لتحلل السكر، حيث يتم أكسدة الجلوكوز إلى البيروفات، مما يؤدي في نفس الوقت إلى اختزال NAD^+ إلى NADH. يتم أيضًا إنتاج جزيئين من ATP بواسطة الفسفرة على مستوى الركيزة.

في الكائنات الهوائية، يتم استقلاب البيروفات عبر دورة حمض الستريك لإنتاج الإنزيمات المساعدة المختزلة NADH وFADH_2. ثم يتم أكسدة هذه الإنزيمات المساعدة في سلسلة نقل الإلكترون لإنتاج ATP. في هذه العملية، يتم تجديد NAD^+ وFAD في الكائنات الحية. يؤدي التخمر إلى اختزال البيروفات إلى اللاكتات في غياب الأكسجين، مما يؤدي إلى أكسدة NADH إلى NAD^+. يسمح تجديد NAD^+ بتحلل السكر بمواصلة إنتاج ATP عن طريق الفسفرة على مستوى الركيزة.

تخمير حمض اللاكتيك

أثناء تخمير حمض اللاكتيك، يقبل البيروفات الإلكترونات من NADH ويتم اختزاله إلى حمض اللاكتيك، وتنتج الميكروبات التي تقوم بالتخمر المثلي حمض اللاكتيك فقط كمنتج التخمير. تنتج الميكروبات التي تقوم بالتخمر غير المتجانس خليطًا من حمض اللاكتيك والإيثانول و/أو حمض الأسيتيك وثاني أكسيد الكربون. يمنع إنتاج حمض اللاكتيك بواسطة الكائنات الحية الدقيقة الطبيعية نمو مسببات الأمراض في مناطق معينة من الجسم. هذا أمر مهم لصحة الجهاز الهضمي مثلا.

تخمير الإيثانول

يستخدم تخمير الإيثانول للبيروفات بواسطة خميرة Saccharomyces cerevisiae في إنتاج المشروبات الكحولية ويجعل منتجات الخبز ترتفع أيضًا بسبب إنتاج ثاني أكسيد الكربون. خارج صناعة الأغذية، يعد تخمير الإيثانول للمنتجات النباتية مهمًا في إنتاج الوقود الحيوي.

تعتبر العديد من منتجات التخمير مهمة تجاريًا، خارج صناعة الأغذية. على سبيل المثال، يتم إنتاج المذيبات الكيميائية مثل الأسيتون والبيوتانول أثناء تخمير الأسيتون والبيوتانول والإيثانول يتم إنتاجه من خلال التخمر الحمضي المختلط.
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البيروفات هو المنتج النهائي لتحلل السكر ، حيث يتأكسد الجلوكوز إلى البيروفات ، مما يقلل في نفس الوقت من NAD + إلى NADH. جزيئان من ATP هما أيضا ...

Education

JoVE Core

Cell Biology

بيولوجيا الخلية

Unit 1

الوحدة الأولى

Introduction to Metabolism

مقدمة في عملية التمثيل الغذائي (الأيض)

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

pyruvate pathways in fermentation

Pyruvate is a key product of glycolysis and can follow different pathways depending on oxygen availability. During glycolysis, glucose is oxidized to pyruvate, NAD+ is reduced to NADH, and two ATP are made by substrate-level phosphorylation. In aerobic organisms, pyruvate then enters the citric acid cycle, which helps produce the reduced coenzymes NADH and FADH2. These coenzymes are later oxidized in the electron transport chain to make ATP and regenerate NAD+ and FAD.

When oxygen is absent, some cells and organisms use fermentation to keep energy production going. Fermentation reduces pyruvate to lactate and oxidizes NADH back to NAD+. This regeneration of NAD+ is important because it allows glycolysis to continue making ATP by substrate-level phosphorylation.

In lactic acid fermentation, pyruvate accepts electrons from NADH and becomes lactic acid. Microbes that carry out homolactic fermentation make only lactic acid. Microbes that carry out heterolactic fermentation make a mix of lactic acid, ethanol and/or acetic acid, and CO2. Lactic acid made by normal microbiota can help prevent pathogen growth in some body regions and supports gastrointestinal tract health.

Pyruvate can also be fermented to ethanol by the yeast Saccharomyces cerevisiae. This process is used to make alcoholic beverages and helps bread rise because it releases CO2. Ethanol fermentation of plant products is also important in biofuel production. Other fermentation products have commercial value too. Acetone and butanol are made during acetone-butanol-ethanol fermentation, and complex organic compounds used in antibiotics such as penicillin, vaccines, and vitamins are produced through mixed acid fermentation.

Pyruvate Pathways in Fermentation

overview of metabolism

Metabolism in Plants, Animals, and Microbes

Metabolism is the set of chemical reactions that keep living cells working. These reactions are linked through many pathways. Together, they support the normal function of cells in plants, animals, and microbes. In plants, sunlight is the main energy source. Chlorophyll pigments in the leaves absorb this light. The plant then uses that energy for photosynthesis. During photosynthesis, water is oxidized to oxygen and carbon dioxide is reduced to glucose. Glucose then serves as a starting...

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Carbohydrates are an important source of energy and a key part of human nutrition. They are made of carbon, hydrogen, and oxygen. One gram of carbohydrate provides four kilo-calories of energy, so carbohydrates are the body’s most efficient instant fuel. Starch makes up about 60% of the carbohydrates people eat. It is broken down by amylase enzymes, but amylase cannot work in the stomach’s acidic environment. That is why starch digestion happens in the mouth and the small intestine. Simple...

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glycolysis: pay-off phase

Glycolysis: ATP and NADH Output

The pay-off phase of glycolysis turns the two three-carbon sugar molecules into ATP, NADH, and pyruvate. By this stage, the cell has already spent two ATP molecules. The remaining reactions recover that investment and add two more ATP molecules and two high-energy NADH molecules. The sixth step oxidizes glyceraldehyde 3-phosphate, a three-carbon sugar made earlier in glycolysis. High-energy electrons are transferred to NAD+, which becomes NADH. A second phosphate group is then added to form...

fates of pyruvate

Pyruvate is a key product of glycolysis and can follow different pathways depending on oxygen availability. During glycolysis, glucose is oxidized to pyruvate, NAD+ is reduced to NADH, and two ATP are made by substrate-level phosphorylation. In aerobic organisms, pyruvate then enters the citric acid cycle, which helps produce the reduced coenzymes NADH and FADH2. These coenzymes are later oxidized in the electron transport chain to make ATP and regenerate NAD+ and FAD. When oxygen is absent,...

role of reduced coenzymes nadh and fadh&#8322;

Electron Carriers in Cellular Energy

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sugars as energy storage molecules

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fats as energy storage molecules

How Triglycerides Fuel ATP Production

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regulation of metabolism

How Cells Control Metabolic Enzymes

Cells control metabolic enzymes to match changing needs and conditions. Different cells use different enzymes and energy levels, and those needs can also change within the same cell over time. Stomach cells, fat storage cells, skin cells, blood cells, and nerve cells do not all need the same metabolic activity. A digestive cell also works harder soon after a meal than it does many hours later. As cell needs change, the amount and activity of enzymes change too. Enzymes lower activation energy,...

positive and negative feedback loops

Homeostasis and Body Feedback Control

Homeostasis keeps body conditions in a steady range through feedback control. Animal organs and organ systems constantly adjust to internal and external changes. This balance is called a dynamic equilibrium because the body keeps adapting while still staying within specific ranges. The goal of homeostasis is to stay near a set point, which is the value the body tries to maintain. A change in the internal or external environment is a stimulus. A receptor detects that change and sends a signal...

key terms and concepts

Explore how pyruvate is used in aerobic respiration and fermentation, including lactic acid and ethanol fermentation, ATP production, and real-world uses.

Pyruvate Pathways in Fermentation | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

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SC.912.L.18.3

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SC.912.L.18.4

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SC.912.L.18.5

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SC.912.L.18.6

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SC.912.L.18.7

A. All living things are composed of four basic categories of macromolecules and share the same basic needs for life.

B. Living organisms acquire the energy they need for life processes through various metabolic pathways (primarily photosynthesis and cellular respiration).

C. Chemical reactions in living things follow basic rules of chemistry and are usually regulated by enzymes.

D. The unique chemical properties of carbon and water make life on Earth possible.

Pyruvate Pathways in Fermentation

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