Fatty Acids synthesisand imporatnce.pptx

Citric acid is a versatile organic acid found in many fruits, especially citrus fruits like lemons, oranges, limes, and grapefruits. Its chemical formula is C6H8O7, and it's classified as a weak acid. Citric acid has a wide range of applications, from food and beverage production to household cleaning and skincare. In this comprehensive description, I'll delve into its properties, uses, production methods, health effects, and environmental impact.

*1. Properties of Citric Acid:*
Citric acid appears as a white crystalline powder or granules. It's odorless and has a tart, sour taste. It's highly soluble in water, making it easy to incorporate into various products. Citric acid is stable at room temperature but decomposes at higher temperatures, losing its acidic properties. It's a chelating agent, meaning it can bind to metal ions, making it useful in certain industrial processes and household cleaners.

*2. Sources of Citric Acid:*
While citric acid occurs naturally in citrus fruits, it's also produced commercially through microbial fermentation, primarily using strains of the fungus Aspergillus niger. This method allows for large-scale production of citric acid to meet the demand in various industries. Additionally, it can be synthesized chemically, although this method is less common due to higher production costs and environmental concerns.

*3. Uses of Citric Acid:*
*- Food and Beverage Industry:* Citric acid is widely used as a flavoring agent, acidity regulator, and preservative in the food and beverage industry. It enhances the flavor of many products and provides a tart taste in sodas, candies, jams, and preserves. It also acts as a preservative, extending the shelf life of packaged foods and preventing discoloration in fruits and vegetables.
*- Pharmaceutical Industry:* Citric acid is used in pharmaceuticals as a pH regulator, excipient in tablets and capsules, and as a flavoring agent in syrups and liquid medications.
*- Cleaning Products:* Due to its chelating properties, citric acid is used in household cleaning products such as descalers, bathroom cleaners, and dishwashing detergents. It effectively removes mineral deposits and stains without the need for harsh chemicals.
*- Cosmetics and Personal Care:* Citric acid is found in skincare products like exfoliating scrubs, facial peels, and anti-aging creams. It helps to promote skin renewal by gently removing dead skin cells and promoting collagen production.
*- Industrial Applications:* Citric acid is used in various industrial processes, including water softening, metal cleaning, and the production of detergents and surfactants.

*4. Production Methods:*
*- Microbial Fermentation:* This is the most common method for commercial production of citric acid. It involves fermenting glucose or sucrose-containing substrates with strains of Aspergillus niger in large-scale bioreactors. The fungus produces citric acid as a byproduct of its metabolism, which is then extracted and purified.
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1. Fatty Acids Biosynthesis

2. Arachidonic acid is referred to as an ω -6 fatty acid because the closest double bond to the end begins six carbons from ω end. Linoleic acid , is the precursor of arachidonic acid , the substrate for prostaglandin synthesis linolenic acid , the precursor of other ω -3 fatty acids important for growth and development

3. SYNTHESIS OF FATTY ACIDS FA are mainly supplied by diet Excessive carbohydrates and proteins are converted to FA which are stored as TAG In humans, fatty acid synthesis occurs primarily in the liver and lactating mammary glands To a lesser extent in adipose tissues­ The process incorporates carbons from acetyl CoA into the grow­ing fatty acid chain, using ATP and NADPH

4. Production of cytosolic acetyl CoA 1 st step Transfer of acetate units from mitochondrial acetyl-CoA to the cytosol The coenzyme A portion of acetyl-CoA cannot cross the mitochondrial membrane; only the acetyl portion is transported to the cytosol. Citrate is produced by the condensation of oxaloacetate (OAA) and acetyl CoA.

5. Carboxylation of acetyl CoA to form malonyl CoA The energy for the carbon-to- carbon condensations in fatty acid synthesis is supplied by the process of carboxylation and then decarboxylation of acetyl groups in the cytosol.

6. Formation of malonyl -CoA Irreversible process Catalyzed by acetyl-CoA carboxylase. The bacterial enzyme has three separate polypeptide subunits In animal cells, all three activities are part of a single multifunctional polypeptide. In all cases, the enzyme contains a biotin prosthetic group

7. In all organisms, the long carbon chains of fatty acids are assembled in a repeating four-step sequence, catalyzed by a system collectively referred to as fatty acid synthase . There are two major variants of fatty acid synthase: fatty acid synthase I (FAS I), found in vertebrates and fungi , fatty acid synthase II (FAS II), found in plants and bacteria. The FAS I is a single multifunctional polypeptide chain ( Mr 240,000 ). The mammalian FAS I is the prototype. Seven active sites for different reactions lie in separate domains. The mammalian polypeptide functions as a homodimer ( Mr 480,000 ). The subunits appear to function independently.

8. Fatty acids elongation Long-Chain Saturated Fatty Acids Are Synthesized from Palmitate fatty acid elongation systems present in the smooth endoplasmic reticulum and in mitochondria Different enzyme systems are involved, and coenzyme A rather than ACP is the acyl carrier in the reaction, the mechanism of elongation in the ER is otherwise identical to that in palmitate synthesis : The double bond is introduced into the fatty acid chain by an oxidative reaction catalyzed by fatty acyl–CoA desaturase , a mixed-function oxidase

9. Fatty Acid Biosynthesis Is Tightly Regulated The reaction catalyzed by acetyl-CoA carboxylase is the rate-limiting step in the biosynthesis of fatty acids, and this enzyme is an important site of regulation. In vertebrates, palmitoyl -CoA, the principal product of fatty acid synthesis, is a feedback inhibitor of the enzyme; citrate is an allosteric activator

10. When the concentrations of mitochondrial acetyl-CoA and ATP increase, citrate is transported out of mitochondria. it then becomes both the precursor of cytosolic acetyl-CoA and an allosteric signal for the activation of acetyl-CoA carboxylase citrate inhibits the activity of phosphofructokinase-1, reducing the flow of carbon through glycolysis .

11. Acetyl-CoA carboxylase is also regulated by covalent modification . Phosphorylation , triggered by the hormones glucagon and epinephrine, inactivates the enzyme and reduces its sensitivity to activation by citrate, thereby slowing fatty acid synthesis . In its active form , acetyl-CoA carboxylase polymerizes into long filaments phosphorylation is accompanied by dissociation into monomeric subunits and loss of activity.

12. when animals ingest an excess of certain polyunsaturated fatty acids , the expression of genes encoding a wide range of lipogenic enzymes in the liver is suppressed. Β - oxidation is blocked by malonyl -CoA , which inhibits carnitine acyltransferase -I