Gastroenterology

Gut microbiota acts like an auxiliary liver, study finds

Microbes in the mammalian gut can significantly change their hosts' amino acid and glucose metabolism, acting almost like an extra liver, according to a new preclinical study by Weill Cornell Medicine investigators.

Health

Guidance on energy and macronutrients across the lifespan

In the long history of recommendations for nutritional intake, current research is trending toward the concept of "food as medicine"—a philosophy in which food and nutrition are positioned within interventions to support ...

Diabetes

Could lack of sleep increase your risk of type 2 diabetes?

Not getting enough sleep is a common affliction in the modern age. If you don't always get as many hours of shut-eye as you'd like, perhaps you were concerned by news of a recent study that found people who sleep less than ...

Inflammatory disorders

Researchers find evidence a natural juice can help gut health

A team of researchers at the University of Missouri is uncovering how the juice from red cabbage, long used in traditional medicine, can alleviate inflammation-associated digestive health conditions such as inflammatory bowel ...

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Acid

An acid (from the Latin acidus/acēre meaning sour) is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red. Chemicals or substances having the property of an acid are said to be acidic.

Common examples of acids include acetic acid (in vinegar), sulfuric acid (used in car batteries), and tartaric acid (used in baking). As these three examples show, acids can be solutions, liquids, or solids. Gases such as hydrogen chloride can be acids as well. Strong acids and some concentrated weak acids are corrosive, but there are exceptions such as carboranes and boric acid.

There are three common definitions for acids: the Arrhenius definition, the Brønsted-Lowry definition, and the Lewis definition. The Arrhenius definition states that acids are substances which increase the concentration of hydronium ions (H3O+) in solution. The Brønsted-Lowry definition is an expansion: an acid is a substance which can act as a proton donor. Most acids encountered in everyday life are aqueous solutions, or can be dissolved in water, and these two definitions are most relevant. The reason why pHs of acids are less than 7 is that the concentration of hydronium ions is greater than 10−7 moles per liter. Since pH is defined as the negative logarithm of the concentration of hydronium ions, acids thus have pHs of less than 7. By the Brønsted-Lowry definition, any compound which can easily be deprotonated can be considered an acid. Examples include alcohols and amines which contain O-H or N-H fragments.

In chemistry, the Lewis definition of acidity is frequently encountered. Lewis acids are electron-pair acceptors. Examples of Lewis acids include all metal cations, and electron-deficient molecules such as boron trifluoride and aluminium trichloride. Hydronium ions are acids according to all three definitions. Interestingly, although alcohols and amines can be Brønsted-Lowry acids as mentioned above, they can also function as Lewis bases due to the lone pairs of electrons on their oxygen and nitrogen atoms.

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