Bài giảng Basic Food Chemistry - Chapter 1: Protein

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1. Content – Amino acid biosynthesis • Essential amino acid (EAA: ensentials) • Non essential amino acid (NEAA: nonessentials) • EAA biosynthesis • NEAA biosynthesis 12/31/2022 by TDLV 2
2. Polar R groups make the amino acid hydrophilic Non-polar R groups make the amino acid hydrophobic
3. AMINO ACID 12/31/2022 by TDLV 6
4. Modified or Unusual Amino Acids
5. GENES AND PROTEINS 12/31/2022Fig. The flow of genetic informationby inTDLV prokaryotes (left) and eukaryotes (right)10
6. The Nitrogen cycle (fixation) Nitrogen fixation by: • Lightning • Bacteria 12/31/2022 by TDLV 12
7. Nitrogenase • Present in Rhizobium bacteria that live in root nodules of leguminous plants • Some free-living soil and aquatic bacteria also possess nitrogenase • Nitrogenase reaction: + - N2 + 8 H + 8 e + 16 ATP + 2 NH3/NH4 + H2 + 16 ADP + 16 Pi 12/31/2022 by TDLV 14
8. Nitrifying Bacteria – NH NO3 3 "Oxidation"
9. Ammonia → Glutamate • amination of a-ketoglutarate by glutamate dehydrogenase occurs in plants, animals and microorganisms
10. Glutamine → glutamate Prokaryotes & plants Glutamate synthase transfers a nitrogen to a-ketoglutarate
11. Amino acid biosynthesis (anabolism) ❑ Non-essential amino acids: synthesized from the products of their catabolism: ▪ 3 phosphoglycerate, pyruvate, acetyl CoA, or the relevant Krebs cycle intermediates (oxaloacetate, a-keto glutarate). ▪ Transamination of a-keto acids that are available as common intermediates ❑ Essential amino acids: synthesized in micro-organisms (bacteria and yeasts) and passed through the food chain until they reach us in our diet. ▪ a-ketoacids are not common intermediates (enzymes needed to form them are lacking); they are present in micro-organisms and plants ▪ fixation of atmospheric nitrogen (by bacteria): inorganic nitrate →amino groups in amino acids. 12/31/2022 by TDLV 22
12. a-keto glutarate → glutamate 12/31/2022 by TDLV 26
13. Aspartate → asparagine 12/31/2022 by TDLV 28
14. 3-phosphoglycerate → serine 12/31/2022 by TDLV 30
15. Serine → glycine 12/31/2022 by TDLV 32
16. SYNTHESIS OF ESSENTIAL AMINO ACIDS • PATHWAYS ONLY IN MICROORGANISMS AND PLANTS – probable evolutionary loss in mammals – pathways are very complicated – actual pathways vary across species! • in contrast to lipid and carbohydrate pathways, which are almost universal • SYNTHESIZED FROM COMMON METABOLIC PRECURSORS – aspartate – pyruvate – Erythrose-4-phosphate & phosphoenolpyruvate – purine + ATP (histidine)
17. Biosynthesis of Amino Acids Highlight : precursors : intermediates in glycolysis, TCA cycle, pentose phosphate 12/31/2022 by TDLV 36
18. Homocysteine → methionine 12/31/2022 by TDLV 38
19. Synthesis of Chorismate 12/31/2022 by TDLV 40
20. ATP + Glutamate + Glutamine + phosphoribosyl pysophosphate → histidine 12/31/2022 by TDLV 42
21. Pyruvate → Leucine • Leucine regulates its own synthesis by inhibiting in earlier steps 12/31/2022 by TDLV 44
22. Synthesis of Lysine, Threonine 12/31/2022 by TDLV 46