chemistry

Pyruvic acid

Pyruvic acid is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Pyruvic acid rather than just read about it. In short: Pyruvic acid (CH3COCOOH) is the simplest of the alpha-keto acids, with a carboxylic acid and a ketone functional group. Pyruvate, the conjugate base, CH3COCOO−, is an intermediate in several metabolic pathways throughout the cell.

Key takeaways

Pyruvic acid belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Pyruvic acid to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Pyruvic acid from memory before moving on to harder problems.

Reference excerpt

Pyruvic acid (CH3COCOOH) is the simplest of the alpha-keto acids, with a carboxylic acid and a ketone functional group. Pyruvate, the conjugate base, CH3COCOO−, is an intermediate in several metabolic pathways throughout the cell. Pyruvic acid can be made from glucose through glycolysis, converted back to carbohydrates (such as glucose) via gluconeogenesis, or converted to fatty acids through a reaction via acetyl-CoA. It can also be used to construct the amino acid alanine and can be converted into ethanol or lactic acid via fermentation. Pyruvic acid supplies energy to cells through the citric acid cycle (also known as the Krebs cycle) when oxygen is present (aerobic respiration), and alternatively ferments to produce lactate when oxygen is lacking.

History In 1834, Théophile-Jules Pelouze distilled tartaric acid and isolated glutaric acid and another unknown organic acid. Jöns Jacob Berzelius characterized this other acid the following year and named pyruvic acid because it was distilled using heat. The correct molecular structure was deduced by the 1870s.

Production Pyruvic acid is prepared by treating tartaric acid with acid. It can also be produced by oxidation of propylene glycol by potassium permanganate or bleach. The hydrolysis of acetyl cyanide, formed by reaction of acetyl chloride with potassium cyanide, represents yet another route:

CH3COCN + 2 H2O → CH3COCO2H + NH3

Structure Pyruvic acid crystallizes as the keto acid, not the enol. The six non-hydrogen atoms are nearly coplanar. More relevant to biochemistry is the structure of the pyruvate anion. Several salts of pyruvate have been examined by X-ray crystallography. These tests confirm that pyruvate anion also exists in the keto form.

Reactivity As a simple, abundant and bifunctional compound, pyruvic acid has been shown to participate in many reactions. Pyruvate reacts with amino acids to give alanine by the process called transamination:

CH3C(O)CO−2 + RCH2NH2 → CH3CH(NH2)CO−2 + RCHO Pyruvic acid self-condenses to give zymonic acid, a cyclic dehydrated dimer:

2 CH3C(O)CO2H → (O=C)(HOC)(HC)C(CH3)(CO2H) + H2O The dehydration can be induced by distillation of pyruvic acid. Zymonic acid in turn forms a variety of derivatives in aqueous solution. Pyruvic acid is a precursor to several types of heterocycles. When treated with phenethylamine, it gives tetrahydroisoquinoline by a sequential condensation/acylation process (Bischler–Napieralski reaction). With ortho-phenylenediamine it condenses to give quinoxalines. Condensation with 4,5-diaminopyrimidine give hydroxypteridines.

Biochemistry Pyruvate is important in biochemistry. It is the output of the metabolism of glucose known as glycolysis. One molecule of glucose breaks down into two molecules of pyruvate, which are then used to provide further energy, in one of two ways. Pyruvate is converted into acetyl-coenzyme A, which is the main input for a series of reactions known as the Krebs cycle (also known as the citric acid cycle or tricarboxylic acid cycle). Pyruvate is also converted to oxaloacetate by an anaplerotic reaction, which replenishes Krebs cycle intermediates; also, the oxaloacetate is used for gluconeogenesis. These reactions are named after Hans Adolf Krebs, the biochemist awarded the 1953 Nobel Prize for physiology, jointly with Fritz Lipmann, for research into metabolic processes. The cycle is also known as the citric acid cycle or tricarboxylic acid cycle, because citric acid is one of the intermediate compounds formed during the reactions. If insufficient oxygen is available, the acid is broken down anaerobically, creating lactate in animals and ethanol in plants and microorganisms (and in carp). Pyruvate from glycolysis is converted by fermentation to lactate using the enzyme lactate dehydrogenase and the coenzyme NADH in lactate fermentation, or to acetaldehyde (with the enzyme pyruvate decarboxylase) and then to ethanol in alcoholic fermentation. Pyruvate is a key intersection in the network of metabolic pathways. Pyruvate can be converted into carbohydrates via gluconeogenesis, to fatty acids or energy through acetyl-CoA, to the amino acid alanine, and to ethanol. Therefore, it unites several key metabolic processes.

Pyruvic acid production by glycolysis In the last step of glycolysis, phosphoenolpyruvate (PEP) is converted to pyruvate by pyruvate kinase. This reaction is strongly exergonic and irreversible; in gluconeogenesis, it takes two enzymes, pyruvate carboxylase and PEP carboxykinase, to catalyze the reverse transformation of pyruvate to PEP.

Compound C00074 at KEGG Pathway Database. Enzyme 2.7.1.40 at KEGG Pathway Database. Compound C00022 at KEGG Pathway Database. Click on genes, proteins and metabolites below to link to respective articles.

Decarboxylation to acetyl CoA Pyruvate decarboxylation by the pyruvate dehydrogenase complex produces acetyl-CoA.

Carboxylation to oxaloacetate Carboxylation by pyruvate carboxylase produces oxaloacetate.

Transamination to alanine Transamination by alanine transaminase produces alanine.

Reduction to lactate Reduction by lactate dehydrogenase produces lactate.

Environmental chemistry Pyruvic acid is an abundant carboxylic acid in secondary organic aerosols.

Uses Aside from its major role in the functioning of living organisms, pyruvic acid is of interest as a reagent in the synthesis of specialized organic compounds as discussed above in the reactivity section.

Illustrations

Worked examples

Example 1 — a first encounter with Pyruvic acid

Start with the simplest possible case. Write down what Pyruvic acid claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Pyruvic acid before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Pyruvic acid ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Pyruvic acid

In research: Pyruvic acid appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Pyruvic acid in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Pyruvic acid is common in secondary-school and first-year university syllabi. It links to neighbouring topics Alpha-keto acids, Cellular respiration, Exercise physiology, so understanding it makes those chapters shorter.
In everyday life: Look for Pyruvic acid outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Pyruvic acid in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Pyruvic acid means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Pyruvic acid out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Pyruvic acid in simple terms?

Why does Pyruvic acid matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Pyruvic acid?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Pyruvic acid.