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

Il piruvato, il prodotto finale della glicolisi, può avere diversi destini metabolici a seconda delle condizioni fisiologiche all'interno dell'organismo.
In condizioni aerobiche, il piruvato viene convertito in acetil-coenzima A, che viene poi incanalato attraverso il ciclo TCA e la catena di trasporto degli elettroni per produrre energia sotto forma di ATP.
Ma, in condizioni anaerobiche, la catena di trasporto degli elettroni non funziona, come si vede nel lievito e nei batteri anaerobi. Quindi, il piruvato viene fermentato in etanolo mentre ossida il NADH in NAD+ . Il NAD+ viene quindi riciclato per ottenere glicolisi.
Nella maggior parte dei vertebrati, le condizioni temporanee di basso ossigeno innescano un'altra forma di fermentazione del piruvato, in cui viene fermentato in lattato, producendo NAD+.
La rigenerazione del NAD+ durante la fermentazione aiuta le cellule a continuare a produrre ATP anche in condizioni di basso contenuto di ossigeno attraverso la glicolisi.
Durante bassi livelli di glucosio nel sangue, il piruvato può anche essere riconvertito in glucosio-6-fosfato mediante un processo chiamato gluconeogenesi. Il glucosio-6-fosfato viene quindi convertito in glucosio, che ripristina il livello di glucosio nel sangue.

xil destino del piruvato

Il piruvato è il prodotto finale della glicolisi, dove il glucosio viene ossidato in piruvato, riducendo contemporaneamente il NAD+ in NADH. Due molecole di ATP vengono prodotte anche mediante fosforilazione a livello del substrato.

Negli organismi aerobici, il piruvato viene metabolizzato attraverso il ciclo dell'acido citrico per produrre coenzimi ridotti NADH e FADH2. Questi coenzimi vengono poi ossidati nella catena di trasporto degli elettroni per produrre ATP e, nel processo, rigenerare NAD+ e FAD. Come osservato in alcuni tipi di cellule e organismi, la fermentazione riduce il piruvato in lattato in assenza di ossigeno, ossidando il NADH in NAD+. La rigenerazione del NAD+ consente alla glicolisi di continuare a produrre ATP mediante fosforilazione a livello del substrato.

Fermentazione dell'acido lattico

Durante la fermentazione dell'acido lattico, il piruvato accetta elettroni dal NADH e viene ridotto ad acido lattico. I microbi che effettuano la fermentazione omolattica producono solo acido lattico come prodotto della fermentazione; i microbi che effettuano la fermentazione eterolattica producono una miscela di acido lattico, etanolo e/o acido acetico e CO2. La produzione di acido lattico da parte del normale microbiota previene la crescita di agenti patogeni in alcune regioni del corpo ed è importante per la salute del tratto gastrointestinale.

Fermentazione con etanolo

La fermentazione etanolica del piruvato ad opera del lievito Saccharomyces cerevisiae viene utilizzata nella produzione di bevande alcoliche e fa lievitare anche i prodotti a base di pane a causa della produzione di CO2. Al di fuori dell’industria alimentare, la fermentazione con etanolo dei prodotti vegetali è importante nella produzione di biocarburanti.

Numerosi prodotti di fermentazione sono importanti dal punto di vista commerciale al di fuori dell'industria alimentare. Ad esempio, durante la fermentazione acetone-butanolo-etanolo vengono prodotti solventi chimici come acetone e butanolo. I composti farmaceutici organici complessi utilizzati negli antibiotici (ad esempio, penicillina), nei vaccini e nelle vitamine vengono prodotti attraverso la fermentazione acida mista.

Questo testo è adattato da <a href="https://openstax.org/books/biology-2e/pages/7-5-metabolism-without-oxygen">Openstax, Biology 2e, Section 7.5: Metabolism without oxygen</a>

xIl destino del piruvato

Il piruvato è il prodotto finale della glicolisi, in cui il glucosio viene ossidato a piruvato, riducendo contemporaneamente il NAD+ a NADH. Due molecole di ATP sono anche ...

Education

Didattica

JoVE Core

Cell Biology

Biologia cellulare

Unit 1

Unità 1

Introduction to Metabolism

Introduzione al metabolismo

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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

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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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regulation of metabolism

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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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