What is citric: Definition and 32 Discussions

The citric acid cycle (CAC)—also known as the Krebs cycle, Szent-Györgyi-Krebs cycle or the TCA cycle (tricarboxylic acid cycle)—is a series of chemical reactions to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins. The Krebs cycle is used by organisms that respire (as opposed to organisms that ferment) to generate energy, either by anaerobic respiration or aerobic respiration. In addition, the cycle provides precursors of certain amino acids, as well as the reducing agent NADH, that are used in numerous other reactions. Its central importance to many biochemical pathways suggests that it was one of the earliest components of metabolism. Even though it is branded as a 'cycle', it is not necessary for metabolites to follow only one specific route; at least three alternative segments of the citric acid cycle have been recognized.The name of this metabolic pathway is derived from the citric acid (a tricarboxylic acid, often called citrate, as the ionized form predominates at biological pH) that is consumed and then regenerated by this sequence of reactions to complete the cycle. The cycle consumes acetate (in the form of acetyl-CoA) and water, reduces NAD+ to NADH, releasing carbon dioxide. The NADH generated by the citric acid cycle is fed into the oxidative phosphorylation (electron transport) pathway. The net result of these two closely linked pathways is the oxidation of nutrients to produce usable chemical energy in the form of ATP.
In eukaryotic cells, the citric acid cycle occurs in the matrix of the mitochondrion. In prokaryotic cells, such as bacteria, which lack mitochondria, the citric acid cycle reaction sequence is performed in the cytosol with the proton gradient for ATP production being across the cell's surface (plasma membrane) rather than the inner membrane of the mitochondrion.
For each pyruvate molecule (from glycolysis), the overall yield of energy-containing compounds from the citric acid cycle is three NADH, one FADH2, and one GTP.

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  1. I

    Magnesium bisglycinate + citric acid = ?

    Hello, I have a question or two that I need help with: What happens when you put magnesium bisglycinate and citric acid into water solution? Does magnesium change form here? Kind regards, IN
  2. Y

    Milk + citric acid or pineapple juice formula? (chemistry)

    I have a chemistry project involving milk coagulation under certain circumstances. One of the circumstances is milk combined with citric acid or pineapple juice. I need to find the chemical formula of this reaction.
  3. I

    Chemistry Citric acid polyprotic acid equilibria

    Using the first equilibrium, H3A <-> H2A- + H+, the [H+] is solved to be 0.01165 M ~ 1.1 * 10^-2 M. Using the second equilibrium, H2A- <-> HA2- + H+, the additional change in H+ is found to be 1.8 * 10^-5 M. The solution says that this second equilibrium is negligible, because 1.1 * 10^-2 M +...
  4. V

    [Cheese making help] Lower pH with citric acid

    I made an account to ask this. I have looked and could not understand any of the formulas I came across. I even looked for calculators, but did not understand how to use them. Milk has a pH of 6.5 to 6.7 (lets use 6.7) And I wish to lower the milk's pH to 4.9 (as an example) How do I...
  5. N

    At what temperature does citric acid decay?

    I am currently performing a school experiment in which I am testing when citric acid decays. We are juicing lemons, filtering them to get a higher concentration of citric acid, placing them in water baths from 10 to 90 degrees Celsius and then titrating them against one mole of sodium hydroxide...
  6. I

    Does Citric acid decompose in a lemon over time?

    Hi! So I am thinking of doing a concentration of citric acid in a lemon lab, by titrating it against sodium hydroxide. I want my independent variable to be time, and so i plan to do it over the span of 25 days, in which I think it will be long enough to show some change. I'm just unsure about...
  7. Safwat z

    Citric Acid pKa: Calculate pH of Molar Concentration

    I got granulated citric acid 99.9% pure Food Grade, my question is which pKa to use in the pH formula since this acid has three pKa values? I am trying to calculate a pH of a certain molar concentration. I appreciate your input. The formula I am using is pH=1/2(pKa-log molar concentration of...
  8. C

    What is the right amount of citric acid and sodiumhypophosphite?

    Homework Statement In the materrials and methods of one article is mentioned that: A specific amount of citric acid and the catalyst sodium hypophosphite (50 % w/w, on weight of citric acid used) was dissolved in the starch solution. My question is how much citric acid and sodium...
  9. R

    Making a 50% solution from Liquid Citric Acid

    I have a bottle of !00% liquid Citric Acid with the label showing Citric Acid and Water as contents. I need a 50% solution of the acid. Do I dilute this with water 50-50?
  10. L

    Sodium bicarb AND citric acid powder?

    Ok, quick question. I know that baking soda is great for heartburn, but why is it in certain medicines, they have sodium bicarb AND citric acid powder? My wife actually uses those two compounds to make bath fizzies. She adds esentual oils to them for health benefits and smells. haha. Anyway...
  11. T

    Sodium Bicarbonate and Citric Acid

    Homework Statement What salt is produced from sodium bicarbonate and citric acid? Just to be clear, this isn't actually homework. I would hope no professor would ever be so hard. I'm not even in chemistry. Although I did take it last year in high school. Homework Equations I really...
  12. R

    PH to Concentration of Citric Acid

    I am working on making Meads (Honey wine) and after speaking to a master Vinter he advised I lower the pH of my starting water & honey mixture to 3.5 for various reasons. I'm interested in experimenting to see if this gives a noticeable taste difference to the mead. I know honey is Basic but...
  13. D

    Citric acid effect on body chemistry pH

    I see a lot of quacky sites about acid/alkaline body chemistry claiming that lemon juice and orange juice make the body alkaline. They both contain citric acid, orange juice also has lots of potassium... I cannot think of any mechanism whereby citric acid would somehow cause a persons body to...
  14. V

    Quick citric acid question

    Homework Statement just a curosity of mine. citric acid is triprotic, with a pKa3 of 5.41, so does this mean that i will be inf ull conjugate base form(3-) at solution pH >5.41 Homework Equations The Attempt at a Solution
  15. A

    Citric acid buffer solution for prac

    Hi Guys, Citric acid has three different values for pKa because it is a polyprotic acid. I am aiming to make a buffer solution with sodium citrate but I am not sure which pKa value to use in the Henderson-Hasselbalch equation. Does anyone have any ideas?
  16. A

    Flame retardant properties of citric acid

    I am planning to use natural sources of citric acid-lemons preferably-to demonstrate a flame retardant mixture using chiefly sodium benzoate(preservative) and ammonium phosphate besides citric acid.Will a natural source work? I suspect the other chemicals in the lemon extract will spoil the...
  17. Sirsh

    Equation for Citric acid reacting with Sodium hydrogen-carbonate

    Hi, Is this the correct equation for Citric acid reacting with Sodium hydrogen-carbonate. C6H8O7 + 3NaHCO3 -> 3CO2 + 3Na+1 + C6H5O73- Is there supposed to be H2O present also??
  18. G

    Concentation of Citric Acid in Fruit Juice

    Homework Statement This is a lab for Chemistry in grade 12. I'll give some basic info I have. Juice substance is Tang. A solution of juice is prepared by dissolving 4.00 grams of crystals in 100.0 mL of solution. The juice solution is then titrated using a given solution of sodium hydroxide...
  19. Y

    How much lime juice to be used iso. citric acid?

    How much lime juice to be used iso. citric acid?? Dear all, I'm now trying to make mozzarella cheese. The recipe wrote that use 1 1/4 tsp. for a gallon of milk (I think US gallon). The problem is I can't find citric acid right now. If I want to try lime juice instead of it, how much of...
  20. S

    Does citric acid decay over time?

    Does citric acid "decay"? Hi I'm preparing about 80 mL of citric acid from anhydrous crystals, using 1g of crystals to 1 mL of de-ionized water. It is for the purposes of etching GaAs with a 3:1 citric acid to H2O2 (by volume) mixture. I wait at least a day after making the acid from the...
  21. T

    Creating a 50% Citric Acid Solution: Step-by-Step Guide

    how can I make a 50% citric acid solution?
  22. J

    ATP in Fatty acid oxidation and citric acid cycle

    At what point in either beta-oxidation or citric acid cycle is ATP used? I see where ATP is produced in citric acid cycle (originally as GTP) as when succinyl CoA is converted to Succinate, but I can't find any part where ATP is required. Apparently according to my lecture notes, it is...
  23. J

    Citric Acid Cycle -matching carbons

    Citric Acid Cycle --matching carbons Which glucose carbons are pyruvate carbons from? I've been trying to get this for hours. please help.. Also how do you trace carbons along the ciric acid cycle?
  24. R

    Uncovering Citric Acid's Chemical Composition and pH

    [SOLVED] pH question... i'm writing a research paper on the organic medicinal massage oils. i need to know the chemical composition of citric acid and it's pH. can anyone help me?
  25. E

    Calculating Citric Acid for pH Adjustment

    How can I calculate the amount of citric acid to add to a solution of a given pH, to achieve another value of pH?
  26. J

    Solving for Grams of Citric Acid in Juice Solution

    [SOLVED] Titration Lab Homework Statement How many grams of pure citric acid in the juice solution when 4.00 g of the juice crystals are dissolved in 100.0 mL solution? The juice solution is titrated using a given solution of sodium hydroxide. The NaOH is titrated into 10 mL of the juice...
  27. K

    Creating a 15% Citric Acid Solution: A Guide

    I have a bottle of 100% pure citric acid. I would like to know how to make a 15% solution of citric acid from this.
  28. L

    Calculate pH of Citric Acid at Various Concentrations

    Hello, i would really appreciate it if someone could help me with this problem. I would like to know the pH of citric acid at various concentrations. 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%. From what i have read it has something to do with its pKa value which for citric acid is...
  29. J

    Exploring Citric Acid in Drinks & Fruits

    hi, iam doing a investigation in my chemistry class. this investigation is totally independent & there is very little help available frm the teachers. so for the investigation they have given some suitable topics on which i can do my practical & other stuff. the topic i choosed is CITRIC ACID...
  30. N

    Pros & Cons of Citric Acid in Lemon Juice

    Hey Guys, Sorry once again i am posting a thread of a boring topic, but seriously i couldn't find any information on the search engines that why i need your help on, the advantages and disdavantages of Citric acid in lemon juice. I found couple of sentences, but i don't know what it means...
  31. N

    Concentration Citric Acid in Lemon Juice?

    Hey there ppl! I am doing an Acid/Base Titration to investigate whether the concentration of citric acid lemon juice, change over a period of 5 days. So i kindda need some help in this experiment, cause we are not allowed to ask our teacher any help! The main purpose of this experiment is that...
  32. wasteofo2

    Why do citric acids increase your bodys alkalinity?

    I was reading through a physiology book and it stated that oranges and other citric fruits actually increase the alkalinity of your body, even though they're acidic themselves. Does anyone have an explanation for this? Thanks, Jacob