Citric Acid

Name and Structure:
Citric Acid is called3-carboxy-3-hydroxy pentanedioic acid normally but it can also be called 2-hydroxypropane- 1, 2, 3- tricarboxylic acid or 3-hydroxypentanedioic acid-3-carboxylic acid Hydrogen citrate.

How it is made:

Citric acid is made in the tricarboxylic acid cycle (TCA cycle) also known as the Krebs cycle or Szent-Gyorgyi-Kerbs cycle. This cycle is a series of enzymatic reactions in aerobic organisms involving oxidative metabolism of acetyl unit. It produces high-energy phosphate compounds, which serve as the main source of cellular energy. At room temperature it is a white crystalline powder.

A simplified view of the TCA cycle:
1. Begins with acetyl-CoA which transfers two-carbon acetyl group to 4-carbon compound (oxalocetate) then form a 6-carbon compound (citrate).
2. It goes through a series of transformations losing two carboxyl groups as CO2. The carbons donated by acetyl-CoA become part of the 4-carbon compound backbone after the first turn of the citric cycle.
3. Most of the energy made in the oxidative steps of the cycle is then transferred as energy-rich electrons to NAD+, forming NADH. For each acetyl group that enters the citric acid cycle, three molecules of NADH are produced.
4. Electrons are transferred to the electron acceptor Q, forming QH2.
5. The four-carbon oxaloacetate has been regenerated, and the cycle repeats.

(diagram below contains a more complex version of the TCA cycle)

How it affects us:

-Citric acid can be used as a food additive. It is used as flavouring and preservative in food and beverages especially in soft drinks. Sour salt which is used in cooking is citric acid.

-We use citric acid in our daily lives. A solution of 6% concentrated citric acid will remove hard water stains from glass without scrubbing. In industries it is used to dissolve rust from steel. It is useful in shampoos to wash out wax and colouring. It is the main ripening agent in the first steps in making mozzarella cheese. It is used by home brewers to modify brewing water for making beer. It is used in lotion and facial mask which can cause skin irritation to people with sensitive skins

-Citric acid is often consumed into the body with minerals such as calcium, which can cause side effects. (the side effects are listed below)
Erosion of tooth enamel: making teeth more susceptible to tooth sensitivity and cavities4.jpg
Heartburn: citric acid can cause the lower esophageal sphincter to relax, thus allowing acid to flow up into the esophagus
Diarrhea, upset stomach or vomiting
Kidney stones: can produce an increase in oxalate production, raising levels in the urine and leading to projection of kidney stones

-Lemon water which contains citric acid can cure heartburn, bloating and belching. It also helps in digesting food to prevent constipation

- Adding citric acid to preserves, fruit deserts, canned vegetables, and meat products will extend the freshness of the products on the shelves. Citric acid is able to fight the effects of bacterial breakdown

-Citrus food like lemon, orange and grapefruit benefit our body. It is proven to breakdown kidney stones by affecting the citric acid balance of urine. (but there is a side effect, look up)

Interesting facts:
-The molecular formula is C6H8O7 with a molar mass of 192.124 g/mol in andhydrous (water-free) and 210.14 g/mol in monohydate.

-It has a density of 1.665 g/cm3 .

-The melting point is 153°C and boiling point is 175°C

-It can be extracted from the juice of citrus fruits by adding calcium oxide to form calcium citrate, an insoluble precipitate that can be collected by filtration. The citric acid can be recovered from its calcium salt by adding sulfuric acid. It can also be obtained by fermentation of glucose with Aspergillus niger and can be obtained synthetically from acetone or glycerol.

-Lemon contains 30-45% juice and the extracted juice contains 4.5-8.5% organic acids (mainly citric acid). It is said that if the citric acid in lemon juice can dissolve a pearl.

-Citric acid makes it easier for the body to absorb some minerals like calcium citrate sometimes added to orange juice.

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