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

Пируват, конечный продукт гликолиза, может иметь несколько метаболических судеб в зависимости от физиологических условий внутри организма.
В аэробных условиях пируват превращается в ацетил-коэнзим А, который затем направляется через цикл ТСА и цепь переноса электронов для производства энергии в форме АТФ.
Но в анаэробных условиях цепь переноса электронов не функционирует, как это наблюдается у дрожжей и анаэробных бактерий. Так, пируват ферментируется в этанол при одновременном окислении NADH в NAD+. Затем NAD+ возвращается в гликолиз.
У большинства позвоночных условия временного низкого содержания кислорода вызывают другую форму ферментации пирувата, при которой он ферментируется в лактат, образуя НАД+.
Регенерация НАД+ во время ферментации помогает клеткам продолжать вырабатывать АТФ даже в условиях низкого содержания кислорода с помощью гликолиза.
При низком уровне глюкозы в крови пируват также может быть преобразован обратно в глюкозу-6-фосфат с помощью процесса, называемого глюконеогенезом. Затем глюкоза-6-фосфат превращается в глюкозу, которая восстанавливает уровень глюкозы в крови.

Судьба пирувата

Пируват является конечным продуктом гликолиза, при котором глюкоза окисляется до пирувата, одновременно восстанавливая NAD+ до NADH. Две молекулы ATP также образуются путем фосфорилирования на уровне субстрата. В аэробных организмах пируват метаболизируется в рамках цикла лимонной кислоты с образованием восстановленных коферментов NADH и FADН2. Эти коферменты затем окисляются в цепи переноса электронов с образованием ATP и в процессе регенерации NAD+ и FAD. Как видно на примере некоторых типов клеток и организмов, ферментация восстанавливает пируват до лактата в отсутствие кислорода, окисляя NADH до NAD+. Восстановление NAD+ позволяет гликолизу продолжать производство ATP путем субстратного фосфорилирования. Молочнокислое брожение Во время молочнокислого брожения пируват принимает электроны от NADH и восстанавливается до молочной кислоты. Микробы, осуществляющие гомолактическое брожение, производят в качестве продукта брожения только молочную кислоту; микробы, осуществляющие гетеромолочную ферментацию, производят смесь молочной кислоты, этанола и/или уксусной кислоты и CO2. Производство молочной кислоты нормальной микробиотой предотвращает рост патогенов в определенных участках тела и важно для здоровья желудочно-кишечного тракта. Этаноловое брожение Этаноловая ферментация пирувата дрожжами Saccharomyces cerevisiae используется в производстве алкогольных напитков, а также заставляет хлебобулочные изделия подниматься за счет выделения CO2. Помимо пищевой промышленности, этаноловое брожение растительных продуктов играет важную роль в производстве биотоплива. Некоторые продукты ферментации имеют коммерческое значение за пределами пищевой промышленности. Например, химические растворители, такие как ацетон и бутанол, производятся в ходе ферментации ацетон-бутанол-этанол. Сложные органические фармацевтические соединения, используемые в антибиотиках (например, пенициллине), вакцинах и витаминах, производятся путем смешанного кислого брожения. Этот текст адаптирован из <a href="https://openstax.org/books/biology-2e/pages/7-5-metabolism-without-oxygen">Openstax, Biology 2e, Раздел 7.5: Метаболизм без кислорода</a>

Пируват является конечным продуктом гликолиза, при котором глюкоза окисляется до пирувата, одновременно восстанавливая НАД+ до НАДН. Две молекулы АТФ также являются ...

Education

JoVE Core

Cell Biology

Клеточная биология

Unit 1

Раздел 1

Introduction to Metabolism

Введение в метаболизм

KEY TERMS AND CONCEPTS

ОСНОВНЫЕ ТЕРМИНЫ И ПОНЯТИЯ

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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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;

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fats as energy storage molecules

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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.18.7

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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