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Flashcards in Final - oral Deck (56):
1

I. 1. Oxidative degradation of fuel molecules.
-Biochemistry of high energy phosphate compounds.
(Structure, biochemical function)
-Metabolism of creatine.
(Structure, synthesis, biochemical function.)
-Thioester bond.

-Intermed.metabolism: enzymatic proc.; degradation/ synthesis of carb., lipids, proteins and nucleic acids.
-Metabolism: anabolism and catabolism
-Most important fuels: sugars (glu) and FA
-High-E-Ps: formed by condensation of 2 mol. of P, by loss of water.
-High-E-bonds: release more than 6 kJ/mol free E when broken
-ATP: most important high-E-P. 2xphosphoanhydride bonds (-30.6 kJ/mol per reaction).
-UTP: biosynthesis of glycogen
-GTP: protein synthesis + GNG
-CTP: lipid synthesis
-GTP, UTP, CTP: connected w. ATP through nucleoside diphosphokinase
-Substrate-level phosphorylation: both 1,3-diP-glycerate and PEP can donate their P to ADP to form ATP
-Creatine P: stores E in muscles of vertebrates. Formed by transfer of a P from ATP. Cat. by creatine phosphokinase.
-Creatine synthesis: by liver – 3 a.a. are precursors; methyl-gr. from methionine, guanidino-gr. From Arginine, acetate from glycine.
-Creatine degr.: creatine->creatinine
-Thioester bond: R-CO-S-R´
*AcCoA: Thioester of acetic acid. Import. key metabolite, from degr. of glu, FA and ketogenic a.a.

2

I. 2.Glycogenesis, glycogenolysis.
(Steps, location, importance) (Regulation, signal pathways of glucagon/adrenaline and insulin.)

-(!) Flashcard for pathway (!)
-GG: Cytoplasm in skeletal m., liver, kidney. Glu->Gly. Stim. by insulin and incr. BSL. Inhib. by glucagon, epinephrine. KeyE; dephosphorylated (active) glycogen synthase.
-GGL: In liver, (kidney), muscle. Gly->glu. Stim. by fasting, bw.meals, physical exercise, glucagon and epinephrine. Inhib. by insulin. KeyE: P.rylated glycogen phosphorylase.
-Glycogen: glu w. UDP->incr.E->activated in liver: glu reserve for maintainance of normal BSL. In muscle: E source for muscular activity.
-Branching enz.: make new branches from gluc residues and part of gly
-Incr. cAMP: inhib. gly synthase, stim. gly phosphorylase
-Adenylate cyclase: incr. cAMP prod. Phosphodiesterase: decr. cAMP prod.
-Insulin: decr. cAMP activation. Activate phosphodiesterase. Receptor tyrosine kinase. 2nd messenger; PIP3
-Glucagon, epinephrine: incr. cAMP activation by activating adenylate cyclase.
-Allosteric regulation: Faster. By binding an effector molecule at a site other than active site. Liver: glu inactivate glyc phosphorylase. Muscle: Ca2+ activate phosphorylase kinase.

3

I. 3.Glycolysis.
Steps, types, location, regulation, energy balance, importance.
The Pasteur effect and Cori cycle.

-(!) Flashcard for pathway (!)
-Break down glucose, to form pyruvates.
-Cytoplasm
-Aerobic: more efficient -> prod. more ATP. With O2 (required to oxidize NADH+H+). 2 pyruvate prod. In cell w. mitochondria.
*E-balance: glu: 2ATP used, 8ATP gained=6ATP, gly: 1ATP used, 8ATP gained=7ATP
-Anaerobic: wØ O2. Lactic acid prod. NADH+H+ oxidized to NAD+ by reducing pyruvate to lactate. ATP prod. in cells without mitochondria.
*E-balance: glu: 2 ATP used, 4ATP gained=+2ATP, gly: 1ATP used, 4ATP gained=-3ATP
-Regulation: Allosteric + hormonal
-Hexokinase: Inhib.: glu-6-P
-P-fru-kinase 1: most imp. reg.Enz. Cat. rate limiting step. Inhib.: incr. ATP, citrate, glucagon. Stim.: incr. ADP, AMP, fru-2,6-P, insulin.
-Pyruvate kinase: Inhib.: incr. ATP, alanine. Stim.: fru-1,6-P.
-Pasteur effect: O2 has an inhib. effect on the fermentation process (lactate prod.)
-Cori cycle: lactate prod. by anaerobic GL in m. is transp. to liver and conv. to glu. Returns back to m. and is metabolized to lactate again.
-Overall prod. of ATP: 36 ATP

4

I. 4. Gluconeogenesis.
(Steps, entry of different substrates, location, regulation, energy balance, importance)

-(!) Flashcard for pathway (!)
-Liver, kidney – cytoplasm
-Synthesis of glucose from non-carbohydrate precursors (lactate, glucogenic aa., glycerol, propionate)
-Necessary for testis, brain, RBC, medulla renalis
-Hormonal regulation: Glucagon; incr. cAMP->stim. GNG. Insulin; decr. cAMP->inhib. GNG
-Allosteric regulation: Fast. Pyruvate carboxylase; stim. by AcCoA, inhib. by ADP. PEP carbocykinase; inhib. by ADP. Fru-1,6-phosphatase: stim. by citrate, inhib. by AMP and fru-2,6-P.

5

I. 5.Oxidation of pyruvate to acetyl~CoA.
(Steps, necessary cofactors, importance.
Glycerol phosphate shuttle)

-(!) Flashcard for pathway (!)
-AcCoA synthesis from pyruvate: oxidative decarboxylation
-Pyruvate in cytosol -> AcCoA in mitochondria, through transport protein
-Transport protein need: pyruvate DH E complex + 5 factors; thiamine pyrophosphate, lipoic acid, HS-CoA, NAD+, FAD
-Steps:
1. Decarboxylation: CO2 removed. TPP needed.
2. Redox R.; NAD+ red. to NADH+H+. FAD needed.
3. Acylation: HS-CoA -> AcCoA. Lipoic acid needed.
-Regulation: Allosteric stim.; pyruvate, Allosteric inhib.; AcCoA, inhib; incr. ATP
-Gly-P-shuttle: Predom. used by skeletal m.cells.
1. Inside cytoplasm: NADH prod. in GL is ox. To NAD+ by red. dihydroxyacetone-P into gly-3-P. Catalyzed by cytoplasmic gly-3-P-DH.
2.Gly-3-P moves into intermembr.space of mitochondria, and is ox. back to dihydroxyacetone-P by isoenzyme version of gly-3-PDH. This E transfers 2 e-+2H+ to FAD and prod. FADH2.
3.Ubiquinone in inner membr. collects 2e-+2H+ and is red. to ubiquinol and FADH2 is ox. back to FAD.
*Under aerobic conditions, NADH prod. in GL must be transported into mitochondria. Inner mitoch.membr. is impermeable to NAD+/NADH -> e- is extracted from NADH to ubiquinone. Ubiquinol pass the e- to complex III.
*NADH from GL bypasses complex I -> only prod. a net result of 1.5 ATP per NADH.

6

I. 6. Citric acid cycle.
(Steps, location, regulation, energy balance, importance.)

-(!) Flashcard for pathway (!)
-Mitoch. matrix
-24 ATP per glu (3 NADH+H+ x 2 -> 18ATP, 1FADH2 x 2 -> 4ATP, 1ATP x 2 -> 2ATP)
-1 glu = 2 x pyruvate -> 2 AcCoA
-Aerobic: O2 needed to reox. the red. NADH+H and FADH2
-Before TCA: pyruvate need to be ox. to AcCoA
-Oxidative decarboxylation
-Factors needed: TPP, lipoic acid, HS-CoA, NAD+, FAD
-Allosteric regulation:
*Citrate synthase; stim. by incr. ADP, NAD+, inhib. by incr. ATP, NADH+H+.
*Isocitrate DH; stim.by incr. ADP, NAD+, inhib. by incr. ATP, NADH+H+.
*Succinate DH; stim. by succinate, inhib. by OAC

7

I. 7.Respiratory chain, oxidative phosphorylation.
(Structure, steps, location, energy balance, importance. P/O proportion, uncoupling factors)

-(!) Flashcard for pathway (!)
Resp.chain: Inner mitoch.membr.
-e- move from e-donor (NADH or QH2) to a terminal acceptor (O2) via series of redox R.
-A proton gradient necessary to prod. ATP
-Complex I, III and IV: 4H+ pumped to intermembr.space
-Complex I: NADH DH. 1.FMN red. to FMNH2. 2.e- transferred from FMNH2 to Fe-S clusters. 3.e- transferred to coE-Q.
-Complex II: Succinate DH. 1.FAH2 ox. to FAD. 2.2e- transferred to Fe-S clusters. 3.2-e transferred to coE-Q.
-Complex III: Cytochrome reductase. Contains cyt. b and c + Fe-S clusters. Catalyse transfer of e- from QH2 to ox. cyt.C, via Fe-S clusters.
-Cytochrome: e-transferring protein containing a hem-prosthetic gr.
-Complex IV: Cyt.C oxidase. Contains cyt.C, a3 + 2 Cu-complexes. Cyt.C ox, O2 red. to H2O. 4H+ and O2 from matrix goes inside, 2H20 is formed and goes back, 2H+ pumped to intermembr.space.
Ox.ppr:
-Coupled to resp.chain by transport of protons to inner mitoch.membr. -> el.+pH-gradient
-Formation of ATP from ADP-Pin, after e-transfer from NADH/FADH2 to O2
-ATP synthesized when protons flow back to matrix through complex
-Uncoupling factors: 1.physiological: thermogenin, long chain FA from lipids. 2.chemical: dinitrophenol
-P/O ratio: Nr. of moles Pin converted to ATP, per atom of O consumed.
-E-balance: overall prod. of ATP from one glu; 36 ATP (GL=4ATP, pyruvate ox.=6ATP, TCA=24ATP)

8

I. 8.The pentose phosphate pathway.
(Steps of oxidative and non-oxidative phase, location, regulation, importance)

-(!) Flashcard for pathway (!)
-Anabolic pathway
-Utilize C6-sugars to generate 5C-sugars -> ribose-5-P -> synthesis of nucleotides and n.a.
-Generate NADPH+H+
-Cytoplasm in liver (FA synthesis), adipose tissue, adrenal cortex, testis and lactating mammary gl.
1.Oxidative: Substrate is glu-6-P. Generate NADPH+H+
2.Non-ox.: Generate ribose-5-P.
-Allosteric reg.: glu-6-DH (key E). Stim. by incr. NADP+., make more NADPH+H+. Inhib. by incr. NADPH+H+, make less.
-Control: both GL and PPP use glu-6-P. ATP needed for GL, NADPH needed for PPP.
-R. is repeated 6 times to get enough carbons
-Antiox.: NADPH+H+ and glutathione
-Erythrocyted use PPP to generate NADPH+H+ used in red. of glutathione
-PPP and GL linked by transketolase and transaldolase; created a reversible link bw. Them by catalysing 3 reacions;
1. Xylose-5-P + rib-5-P gly.ald.-3-P + sedoheptulose-7-P
2. Gly.ald.-3-P + sedoheptulose-7-P fru-6-P + erythrose-4-P
3. Erythrose-4-P + Xylose-5-P fru-6-P + gly.ald.-3-P
Net R.: 3-rib-5-P (15C) 2-fru-6-P (12 C) + gly.ald.-3-P (3C)

9

I. 9.Blood sugar level and its regulation.
(Physiological values of blood sugar level. Hormonal regulation of blood sugar level, intracellular regulatory mechanisms, signaling pathways. Transporters of glucose circulation)

-Blood glu.=transport form of carbs.
-Ru: 2-3 mmol/L, other mammals: 4-5 mmol/L, poultry: 8-9 mmol/L
-Glu.transportes: GLUT-1(brain+RBC), GLUT-2(liver+kidney), GLUT-3(brain), GLUT-4(muscle+adipose tissue, insulin dependent)
-Insulin dependence: binds to receptor that induce a signal transduction cascade allowing GLUT-4 to transport glu. to the cell.
-Placenta of Ung. prod. fru. -> fetal fru.conc. higher than glu.conc.
-Glu-precursor: glu-6-P
-Glu-6-phosphatase: only in ER of liver and kidney
-Hormonal regulation:
1.Glucagon: Prod. by alpha-pancr.cells. Stim. liver only. Effect: Hyperglycaemia. Affected P: +liver GNG, +GNG, -liver GG, -GL.
2.Epinephrine: Prod. by adrenal medulla. Stim. muscle only. Effect: Hyperglycaemia. Affected P: +muscle GGL, -muscle GG.
3.Glucocorticoids: Prod. by adrenal cortex. Effect: Hyperglycaemia. Affected P: +GNG from aa., -GL.
4.ACTH: Prod. by adrenohypophysis. Effect: Hyperglycaemia. Affected P: + (indirect) incr. GNG -> incr. BSL secretion
5.Somatropin/growth hormone: Prod. by adrenohypophysis. Effect: Hyperglycaemia. Affected P: +LL, -GNG from aa.
6.Insulin: Prod. by beta-pancr.cells. Effect: HYPOglycaemia. Affected P: +glu uptake, +GG/GL, -GGL/GNG, -fat+prot. degr.
-Hyperglycaemia: glu leave liver-cells to enter blood circ. Incr. BSL back to normal level when BSL is to low.
-Hypoglycaemia: glu removed from blood and enter cells for storage/utilisation. Decr. BSL back to normal when BSL is to high.

10

I. 10. Metabolism of fructose and galactose.
Synthesis and degradation of fructose. Synthesis of galactose, its entry in the synthesis of lactose and mucopolysaccharides, galactolysis.
Biochemistry of milk production.
The components of milk. Synthesis of lactose, milk proteins and milk fat.

-(!) Flashcard for pathway (!)
Fru.metabolism: (compounds of sucrose)
1.Ingested fru is phosphoryl. at C1 to fru-1-P by fructokinase.
2.Fru-1-P is split into dihydroxyacetone-P and gly.ald.
3.Gly.ald. is phosphoryl. to gly.ald.-3-P.
4. Gly.ald.-3-P + dihydroxyacetone-P can enter GL
Gal.metabolism: in intestinal tract by enzymatic hydrolysis of lactose
1.Liver: gal. is phosphoryl. by galactokinase to yield gal-1-P
2.Gal-1-P is converted to glu-1-P through a sequence of R requiring UTP
3.Glu-1-P enters glycolytic P
Biosynthesis of milk:
-Contains: fat, carb., prot., inorg.salts (-Fe and Cu), vitamins
-Major E-source: glu, free aa., acetate, beta-HB, TAGs, non-esterified FA
Biosynthesis of milk fat:
-Contains: TAGs mainly, P-lipids, chol., free FA
1.Chylomicrons+lipoprot. of blood plasma are hydrolysed by lipoprotein lipase (activ. by heparin). Major protein of FAs absorbed by mam.gl. FAs then converted to TAGs.
2.Acetate+b-HB: major precursors of milk FAs in de novo synthesis. B-HB conv. to acetate. Acetate activ. in cytosol to AcCoA by AcCoA synthase.
Biosynthesis of lactose: Only by mam.gl.
-Glu=blood precursors (2kg glu taken up daily by mam.gl)
-Only small amount of glu abs. from digestive tract -> GNG responsible for larynx glu prod.
-Synthesis: formed from glu and UDP-galactose by lactose synthetase sys.
Biosynthesis of milk prot.:
-Tot.milk prot; 33g/L
-Proteins: casein, globulin and a-lactalbumin (de novo synthesis, mam.gl.), milk serum albumin and Igs (from blood)

11

I. 11.Oxidative deamination of amino acids.
(Oxidative deamination of L- and D-amino acids.)
Fate of the nitrogen-free carbon chain of amino acids.
(Glucogenic and ketogenic amino acids.)
Transamination of amino acids.
(Transamination reactions in general, AST, ALT. Production of Schiff-base and the mechanism of transamination.)

Ox.deamination of aa: degradation
1.Glutamate: L-glutamate+NAD+ +H2Oa-ketoglutarate+NH3+NADH+H+
-L-glutamate DH: Mitoch. CoE; NAD+ + NADP+. Allosteric reg.; stim. by ADP+GDP, inhib. by ATP+GTP.
2.D-amino oxidases: ox. ingested D-aa. derived from cell walls of bacteria. Prost.gr.; FAD. In peroxisomes of liver cells.
-D-aa.+FAD+H2O->a-keto acid+NH2+FADH2
-Catalan(in peroxisomes of liver cells): decomposes H2O2 to H2O and O2
Fate of C-atoms of degraded aa.:
-Ketogenic aa: D-aa. that are degr. to AcCoA (or Acetoacetyl CoA) and capable of forming KBs.
-Glycogenic aa: D-aa. that are degr. to pyruvate, a-ketoglutarate, succinyl-CoA, fumarate or OAC.
-Leucine: can´t yield net form. of glu (all C are conv. to CO2/AcCoA), only ketogenic
-Isoleucine, lysine, phenylalanine, tyrosine: both gluco- and ketogenic because in degr. they´re cleaved to form fumarate, succinyl-CoA or pyruvate(glucogenic) and acCoA(ketogenic)
Transamination of aa.:
-Cat. by transaminases: coE; pyridoxal P (PALP)
-Aspartate transaminases(AST): glutamate+OAC a-keto-glutarate+aspartate
-Alanine transaminases(ALT): glutamate+pyruvatea-ketoglutarate+alanine
-Transaminase: prominent in liver, skeletal m., heart. In mitochon.+cytosol.
1.Amino gr. of most aa. are removed in cytosol by transam. to pyruvate, OAC or a-ketoglutarate.
2.All amino gr. are collected by transam. To a-ketoglutarate, yielding glutamate.
3.Glutamate enters mitoch.; a) deamin. By L-glutamate DH b)amino gr. is transfered to OAC yielding aspartate

12

I. 12. Essential and non-essential amino acids.
Decarboxylation of amino acids. Biogenic amines and their degradation. Biochemistry of glutathione, gamma-glutamyl cycle. Carnosine and anserine.

-Nonessential aa: Required for normal health and growth. Can be synthesized within body or derived in body from essential aa.
-Essential aa: Must be obtained from oxogenous sources, can´t be synthesized within body.
-Bacteria: can synthesize all of the 20 aa.
-Ru: can receive their essential aa. through microbial synthesis in rumen
-Chickens: glycine is essential because the purine synthesis in the liver requires a high amount of glycine
-Limiting aa.: limiting factors in nutrition
Decarboxylation of aa: E=decarboxylan. Cofactor=PALP. Aa amine + CO”
-Decarboxylans: animal tissues, especially liver, kidney and brain. Several amines also formed in gut by bacterial decarboxylans.
Biogenic amines and their degradation:
-Most important amines: Histamine (capillary dilator, allergic R), serotonin (vasoconstriction), tyramine (SM constrictor), cysteamine + B-alanine, ethanolamine, G-amino-butyrate, cadaverine + putrescine
Biochem. of glutathione:
-tripeptide: gamma-glutamy-cysteinyl-glycine
-Important role: in ox-red-proc. R-SH+R-SHR-S-S-R
Carnosine and anserine: dipeptides
-Carnosine: B-alanyl-histidine. Constituent of m. in mammals.
-Anserine: B-alanyl-I-methylhistidine. Constituent of m. in birds.

13

I. 13. Detoxification of ammonia.
Urea cycle (steps, location, regulation, energy balance, importance). Alternative detoxification pathways.

-(!) Flashcard for pathway (!)
-Ammonia: Toxic. Derived from ox.deamin. Leads to amination of a-ketoglutarate, catalysed by L-glutamate DH.
-a-ketoglutarate + NH3 + NADH+H+ L-glutamate + NAD+ + H2O
-NH3 removes a-ketoglutarate from TCA and causes severe inhib. of cell resp.
-Mammals: most excess NH3 is converted to urea. Some can be excreted as NH4+ by kidney.
-Birds: terrestrial reptiles convert NH3 into uric acid
-Many aquatic animals: excrete NH3.
Urea cycle: Convert toxic NH3 into less toxic urea. Require E (ATP). In liver only.
-Urea=neutral water-sol.molec, excreted in urine
-Start molecule: free NH3 prod. from deamin. of L-glutamate in mitochondria
-Allosteric inhib. in step.1: N-acetyl-glutamate
-Synthesis of fumarate: links TCA with urea cycle
-Overall R: 2NH3 + CO2 + 3ATP + 2H2O -> urea + 2ADP + 2Pin + AMP + PP
-Formation of NH4+: in close connection to metabolism of glutamate; 1.Diff. aa. is transam. To glutamate. 2.Glutamate is converted into glutamine after uptake of an NH3
-Glutamine: transport form of NH3. Formed by glutamine synthetase
Glutamate + NH3 + ATP –(glutamine synthetase)-> glutamine + ADP + Pin
-Glutamine gives up free NH3 into kidney tubules, catalysed by glutaminase.
Glutamine + H2O -> glutamate + NH3
-The released NH3 can accept H+ and will be converted to NH4+

14

I. 14. Synthesis and degradation of purine nucleotides.
De novo synthesis, degradation, resynthesis, deoxyribonucleotides.

-Purine: aromatic heterocyclic compound derivate of pyrimidine. Consist of fused pyrimidine and imidazole rings.
-Synt+degr.: cytosol-each cell type
-PRPP: key intermediate in both purine and pyrimidine biosynthesis.
-Inosinate: important intermed. prod. of biosynthesis
De novo synthesis:
1.PRPP reacts with glutamine to form 5-P-ribosyl-1-amine, free glutamate + pyrophosphate.
2.The purine ring is formed in the next steps, utilizing precursors and ATP mol. In the final step inosinate forms the ring.
3.AMP and GMP are prod. after two phosphoryl. catalysed by phosphokinases.
-Controlled by feedback inhib.
-Regulatory E: PRPP synthetase (catalyzes form. of PRPP). Inhib. by AMP and GMP.
-Purine can also by synthetized from preformed basis by a salvage R. Catalyzed by specific transferases.
Degradation: nucleotides -> nucleosides: by nucleotidases
-Phosphorolytic cleavage of nucleoside to free bases and rib-1-P catalysed by nucleoside phosphorylases.
-Rib-1-P is isomerized by phosphoribomutase to rib-5-P
Resynthesis: some bases are reutilized to form nucleotides by salvage R.
Deoxyribonucleotides:
-Formed from ribonucleotides by red.
-All 4 ribonucleosides diP (ADP, GDP, VDP and CDP) can be directly red. to corresponding deoxy analog.
-Ribonucleotide diP + NADPH+H+ -> deoxyribonucleoside diP + NADP+ + H2O
-Ribonucleoside diP reducats: allosteric inhib.; dATP

15

I. 15. Synthesis and degradation of pyrimidine nucleotides.
De novo synthesis, degradation, resynthesis, deoxyribonucleotides.

-(!) Flashcard for pathway (!)
Synthesis:
-Cytoplasm in each cell type
-Need a lot E –> 7 ATP
-Regulation: Feedback inhib., carbamoyl P synthetase (inhib. by UMP), Asp carbamoyl transferase (inhib. by CTP)
Degradation:
-In cytoplasm of each cell type
-Regulation: depends on amount of nucleotides to be degraded

16

I. 16. Structure and biochemical role of haemoglobin. Synthesis of haemoglobin.
Steps, location, regulation, importance.

-(!) Flashcard for pathway (!)
Structure:
-Formed by conjugation of basic prot., globin with heme
-Hemoglobin A: major haemoglobin in adults. Consist of 4 poypetides (2 a-chians, 2 b-chains) and 4 hemes. Heme residue bound to polypeptides w. non-covalent linkage.
-The iron atom in heme binds to 4 N in the centre of the protoporphyrin ring
-The iron can form 2 addition bonds: 1) 5th coordination position (imidazole N of a histidine residue) 2) 6th coordination position (oxygen-binding site)
Biochem. role:
-Prim. function in blood: transport O2 from lungs to tissues
-Dissociable Hb-O2-complex: (deoxy)Hb + O2 oxyhemoglobin
-Each heme can bind one O2 mol. Incr. binding per O2 mol.
-MethHb: Fe3+ instead of Fe2+. Can´t bind O2.
-Hb bound to CO forms carboxyHb. Binds to CO 3-400x than O2.
-Biosynthesis:
1.All C of porphyrin are provided by succinyl CoA and glycine -> d-aminolevulinic acid
-D-aminolevulinic acid synthetase: cofactor; PALP. Rate controlling step. Allosteric inhib.; accumulation of endprod., Heme.
2.Two d-aminolevulinic acid condense to form porphobilinogen, by d-aminolevulinic acid DH
3.Condensation of 4 porphobilinogen forms protoporhyrin IX
4.Fe2+ goes into protoporhyrin spontaneously, but incr. by ferrochelatase.
-Hb A: formed in red BM of adults
-Hb F: synthesized in liver. In human + calf fetus. 2 a-chains+2 g-chains

17

I. 17. Degradation of porphyrines.
Myoglobin, cytochromes, catalase, peroxidase.
Iron metabolism.

Degradation:
-Avg. lifespan of erythrocytes: 60-160d
-Old cells removed from circ. by spleen.
-Globin: hydrolysed to aa., which are used in protein synthesis.
-Heme:
1.Cleavage of a-methene bridge to form biliverdin. Cat. by heme oxygenase. Need O2, NADP. Fe3+ released and reused for form. of new Hb mol.
2.Central methane bridge of biliverdin red. by biliverdin reductase to form bilirubin. Need NADPH.
3.Bilirubin transp. to liver by binding to albumin.
4. Bilirubin dissoc. from albumin and enters hepatocyte.
5. In liver: bilirub esterified into bilirubin diglucuronide by addition of 2 glucuronic acids.
6.Bilirubin diglucuronide is secreted into bile.
7.In int.: bilirubin diglucuronide hydrolysed and red. by bacterial E into UBG and SBG.
8.Some UBG/SBG ox. to urobilin/stercobilin.
Myoglobin: small globular prot. Contains a single polypept.chain of 153 aa. and a iron-porphyrine heme gr. like Hb.
-(deoxy)myoglobin + O2 oxymyoglobin
-In heart and red skeletal m. fibres
-Function: O2 carrier and –storage
Cytochromes: Hemoproteins. Iron atom is reversibly converted from Fe3+ to Fe2+. Reversible carrier of e- in resp.chain.
-3 major classes: cyt.a+a3, cyt.b, cut.c
-Cyt.a+a3 inhib. by CO + cyanide
Catalase+peroxidase: Hemin E. Contain Fe3+-protoporphyrin IX. React w.H2O2.
Catalase: 4 subunits. Cat. decomposition of toxic H-peroxide.
Peroxidase: cat. overall peroxidatic R.
Iron metabolism:
-Iron absorption: dietary iron-usually Fe3+ form
1. Enter acidic environment of stomach; release iron from prot. and maintain available Fe3+ and Fe2+ in sol.
2.Alkalinic environment of Ascorbic acid red. Fe3+ to Fe2+.
Controlled by: Apoferritin in mucosal cells
-Iron transport: transferrin bind 2 Fe3+ and transport it in plasma
-Iron storage: iron not required for Hb and myoglobin synthesis is transferred to reticuloendothelial cells of liver, spleen and BM for incorporation into the iron storage compounds.
-Iron excretion: very low. Large amount in feces. Small amount in exfoliated skin cells, hair, nails, milk and urine.

18

I. 18. Absorbtion and circulation of lipids in the organism. Lipolysis (Steps, location, regulation, importance)
Lipogenesis (Steps, location, regulation, importance)

Lipids: water insol organic subst. in animal + plant cells.
-Extractable by nonpolar solvents
-Groups: fats and lipoids
Fats: neutral; FA of glycerol.
FA: saturated(no double bonds)/unsaturated
-Saturated: palmitic-, stearic-, oleic-, linoleic-, linolenic- and arachidonic acids.
-FA stored in adipocytes as TAG
-Mobilization initiated by HSL; removes FA from TAG
-HSL activated when hormones binds to receptor on cell membr. and activate adenylate cyclase, which cat. synthesis of 2nd messenger, 3,5-cyclic AMP from ATP. cAMP activate protein kinase -> activate HSL in cascade of R.
Lipogenesis: cytoplasm – adipose tissue, liver, mammary gland
-Lipids only begin digestion in small intestines, and must be broken down before absorbed.
-Resynthetised once taken up
-Lymph: main transporter for TAG, stored in liver, muscle or adipose tissue
-Three lipase E w. diff. effects
Lipolysis: breakdown of fats into glycerol and FA. FA can undergo b-ox. while glycerol is further catabolized into an intermediate of GNG or GL.

19

I. 19. Degradation of fatty acids: beta-oxidation.
(Transport of fatty acids into the mitochondrial matrix. Steps of beta-oxidation of fatty acids with even carbon atoms. Location, regulation, energy balance, importance. Specificities of beta-oxidation of unsaturated fatty acids and fatty acids with odd carbon atoms)

-(!) Flashcard for pathway (!)
-Mitochondria
-FA must be transport through inner membr. of mitoch., 2 stages:
1.Conversion of the coA derivate
2.Transport of fatty acyl gr. by specialized carrier molecule; carnithine
-Carnithine acyltransferase I: regulatory E. Allosteric stim.: high conc. of free FAs. Allosteric inhib.: malonyl CoA
Beta-ox.: recurring sequence of 4 R resulting in shortening of C-chain by 2 C:
1.1st DH step that prod. FADH2
2. Hydration
3. 2nd DH step that prod. NADH
4. Thiolytic cleavage that releases a molec. of AcCoA
-E-balance: 1 mol. Of palmiotyl CoA:
overall eq.: palmiotyl CoA + 7HS-CoA + 7FAD + 7NAD+ + 7H2O -> 8CH3-CO-S-CoA + FADH2 + 7NADH + 7H+
-Ox. in resp.chain to CO2 and H2O yields: 131 ATP
-2ATP needed for prod. of palmiotyl CoA from palmitic acid: 129 ATP
Ox. of odd-C FAs:
-By same general pathway as sat. FAs, but 2 problems occur:
1. The double bonds of nat. occurring unsat. FAs are in cis-config. -> the unsat. Acyl CoA ester are in trans-config.
2.The position of the unsat. Bonds yields beta, gamma, unsat. Fatty acyl CoA instead of alpha, beta, fatty acyl CoA, and the E enolhydratase can´t hydrate them -> cis,trans isomerase instead.
-Cis, trans isomerase: cat. the shift of ouble bond from beta, gamma to alpha, beta pos. + from cis to trans config

20

I. 20.Synthesis of fatty acids.
(Transport of acetyl~CoA to the cytoplasm. Steps of synthesis of fatty acids with even carbon atoms. Location, regulation, importance. Specificities of synthesis of unsaturated fatty acids and fatty acids with odd carbon atoms.)

-(!) Flashcard for pathway (!)
-Cytoplasm, mainly in adipose tissue and liver
Transport of Ac-CoA to cytoplasm:
-Non-Ru: major part of Ac-CoA prod. in mitoch.
-Ac-CoA need to be transported to cytosol for FA synthesis
-Mitoch.membr. not permeable to Ac-CoA
-Citrate formed in mitoch.matrix by condensation of Ac-CoA and OAC -> diffuses to cytosol where it´s cleaved by citrate lyase: citrate + ATP + HS-CoA -> Ac-CoA + ADP + Pin + OAC
Synthesis of even-C FAs:
1.Carboxylation of Ac-CoA to malonyl CoA: irreversible, cat. by Ac-CoA carboxylase (pr.gr.; biotin), pos.allosteric regulator; citrate, neg. allosteric regulator; end prod.-palmiotyl CoA
-Further steps: cat. by a complex of 7 E called fatty acyl synthetase complex (need Ac-CoA, malonyl-CoA, NADPH mol.)
FA synthetase complex:
1.Transfer of acetyl+malonyl gr.: Acyl gr. transferred to thiol gr. of acyl carrier protein, cat. by acetyl transacylase + malonyl transacylase
2.Condensation R: acetyl gr. condenses w. malonyl gr.
3.First red.: AcAc-5-ACP undergoes red. w. NADPH to form D-steroisomer of b-hydroxybutyryl-5-ACP, cat. by reductase 1.
4.Dehydration R: D-b-hydroxybutyryl-5-ACP is dehydrated to a, b,-unsat. Acyl-5-ACP by enoyl dehydratase.
5.2nd red.: a,b-unsat. acyl-5-ACP is red. to butyryl-5-ACP by reductase II. NADPH is the H-donor.
-Overall R for palmitic acid synthesis: 8 CH3-CO-S-CoA+14NADP+14H+ + 7ATP->palmitic acid+8HS-CoA+14NADPH+ + 7ADP+7Pin
Synthesis of unsat. FAs: stearic acid is precursor of olec acid
-E: oxygnase, located in ER, in adipose tissue+liver (need mol. Oxygen+NADH/NAPDH)
-Stearoyl CoA+NADH+H+ + O2->Oleoyl CoA + NAD+ + 2H2O
-Animals can´t synthetise linolenic acid or linoleic acid (lack E to introduce double bonds at C beyond C9)
Synthesis of odd-C FAs: diff. is in first step only; proprionyl CoA instead of Ac-CoA

21

I. 21.Ketogenesis, ketolysis.
(Steps, location, energy balance, importance. Biochemical function of ketone bodies)

-(!) Flashcard for pathway (!)
Ketogenesis: synthesis of KBs by breakdown of FAs
-Happens when Ac-CoA is in excess amount/not sufficient amount of OAC available -> AcCoA can´t enter TCA. KB are prod. from Ac-CoA and transported via blood to peripheral tissues where they can be ox.
-During fasting, diabetes…
-In mitoch. in liver
1.LL in adipose tissue to incr. level of circ. free FAs.
- + low plasma glu. level: glucagon secr. Induce LL
- - in well-fed state: insulin inhibits KG via triggering diphosphorylation and inactivation of HSL in adipose tissue.
-HMG CoA synthetase: cat. the rate-limit. Step. Present in significant quantities in liver only. + Incr. FAs
2.Fate of FA: free FAs are either ox. to CO2 or KBs, esterified to triacylglyc. and P-lipids.
-Carnithine transferase 1: activ. by low conc. of mal-CoA. In well-fed state; incr. insulin -> red. plasma free FAs conc. -> incr. conc. of mal-CoA -> inhib. the E
3.Fate of Ac-CoA: can be either ox. in TCA cycle or enter KG to form KBs. High plasma conc. of free FAs -> more of them converted to KBs, less ox. to CO2 via TCA cycle. No OAC available -> KG occur
Ketolysis: degradation of KBs
-In heart, muscle, brain
1.Free Acetoacetate+b-hydroxybutyrate diffuse from liver cells to circ. to peripheral tissues
2.KL in peripheral tissues
3.Prod.-2 Acetyl CoA enter TCA cycle
Energy balance: 6NADH(18ATP)+2FADH2(4ATP)+2GTP(2ATP)=24ATP
KBs: acetoacetate, actone, beta-hydroxybutyrate
-E-source for tissues
-Utilization of KBs at extrahepatic tissues:
1.Well-fed, healthy condition
2.Early stages of starvation
3.Prolonged starvation

22

I. 22.Biochemistry of cholesterol.
(Structure, synthesis (steps, location, regulation, importance) and biochemical function of cholesterol. )
Biochemistry of bile acids.
(Synthesis, circulation and biochemical function of bile acids)

Cholesterol: sterol (steroid w. alcoholic hydroxyl gr. at C3 + branched aliphatic chain of 8 or more C at C17)
-Constituent of: plasma membrane, mitoch. membr., ER membr.
-Other roles: precursor of steroid hormone, bile acids + vit.D
-Structure: OH at C3, 8-membr.branched HC-chain at C17 (D-ring), one –CH3 at C10 and on C13, double bond in B-ring bw. C5-C6
-Organs rich in cholesterol: brain, NS, adrenal cortex, liver, (bile)
-Can be obtained from diet or synthetized de novo
-De novo synthesis: all 27 C are derived from Ac-CoA
-Excretion: 1.converion to bile acids->feces 2.solubilization of cholesterol in bile->transported in intestine for elimination
Bile acids: from degradation of cholesterol
-In liver only
-Prim: cholic acid and chenodeoxycholic acid
-Bile salts: bile acids conjugated w. glycine/taurine by peptide bond bw. carboxyl gr. of bile acid and amino gr. of glycine/taurine -> glycocholic/taurocholic acid. Before leaving liver.
*Important in fat digestion (enable to lower surf. tension, lipase can´t act more sufficiently)
-Cholyl CoA=activated bile acid
1.Cholic acid + ATP + HS-CoA -> cholyl CoA + AMP + PP
2.Cholyl CoA + glycine -> glycocholic acid + HS-CoA
-In intestine: bacteria remove some glycine/taurine from bile salt, and convert the prim. to sec. bile acids by removing one hydroxyl gr. -> deoxycholic acid (from cholic acid), litocholic acid (from chenodeoxycholic acid)
-Prim.+sec. bile acids is reabsorbed and reused via enterohepatic circ.

23

I. 23.Carbohydrate metabolism of ruminants. (Degradation of carbohydrates in the rumen, production, absorption and metabolism of volatile fatty acids in the organism)

-(!) Flashcard for pathway (!)
-Metabolism of volatile FAs: short chain FA, e.g.acetate, proprionate, butyrate. Prim. E-source.
-Nearly all food in Ru is plant origin -> carbs. predominant component
-Carbs in plants: 1)non-structural polysaccharides 2)structural polysaccharides
-Non-structural: storage material for E. Sucrose or starch
-Structural: cellulose+hemicellulose most significant
-Degradation:
1.Attachment of microorganisms to plant particles and dissociation of large carb.polymers
2.Hydrolysis of released polymers to small monosaccharides, mainly glu
3.IC fermentation of glu to volatile FAs
-Formation of VFAs in Ru fermentation:
1.pyruvate->acetate 2.pyruvate->proprionate 3.pyruvate->butyrate
-Methane prod. in rumen: from red. of CO2 by H2P
-Form. of VFAs from proteins: most aa. are degraded in rumen to NH3, CO2, VFAs or branched chain FA. Anaerobic mechanism->non-ox. deamination which prod. VFAs.
-Absorption of VFAs: affects buffer capacity in rumen. Simple diffusion. The rate incr. with chain length. Decr. pH incr. the VFA abs. rate.
-Metabolism of acetate: used by peripheral tissues. Activ. in cytoplasm of peripheral tissues into Ac-CoA by Ac-Coa synthetase
-Metabolism of butyrate: rumen mucosa convert ca. 50% of absorbed butyrate to hydroxybutyrate, rest by liver (converted to Ac-CoA and enters TCA)
-Metabolism of proprionate: over 90% of the abs. proprionate is removed from portal blood by liver.

24

I. 24.Metabolism of nitrogen-containing compounds in ruminants. (Production and absorption of ammonia in the rumen. NPN agents, bypass proteins. Bacterial protein production in the rumen. Ruminohepatic nitrogen- circulation)

4 essential stages of N metabolism in rumen:
1.Protein degradation: often by bacteria and protozoa. Two steps; 1.proteolysis (prot. chain broken by hydrolysis of peptide bonds resulting in peptides and aa) 2.deamination
-Bacteria: outside bact. Wall. The peptides + aa are transported inside bact. Cell and peptides further hydrolysed into aa
-Protozoa: engulf small feed particles. Inside protozoal cell.
-Bypass protein: portion of dietary prot. escaping rumen degradation
2.NH3 prod.: Two types; 1.Degr. of aa (ox.deamination) 2)degr. of NPN (urease from rumen bacteria hydrolyzes urea to NH3 and CO2)
3.Microbial protein synthesis: during rumen digestion, microbes multiply and synthetize microbial prot. using dietary prot. or NPN as source for N. Requires E, main source is breakdown of carbs.
4.Absorp. of NH3: by microbes, through rumen wall or flushed in abomasum. Passively, in non-ionized form (diffusion). Decrease pH.
Ruminohepatic N-circ.
-Liver: the abs. NH3 is detoxified by conversion to urea
-NHR intoxication: when it escapes to peripheral bloodstream by exceeding livers capacity for detoxification or by uptake from rumen directly into lymphatic sys.
-Urea recycled into rumen via saliva or attenuated diffusion into ruminal epithelium

25

I. 25.Biochemical background of ketosis in ruminants (connection between gluconeogenesis and ketogenesis. Development and features of ketosis)
Lipid metabolism in ruminants (synthesis and degradation of lipids in the rumen. Characteristics of lipid metabolism of ruminants)

Ketosis: A condition charact. by raised levels of KBs in body. Assosiated w. abnorm. fat metab. and diabetes mellitus.
-Acetone: non-metabolized side-prod. secr. w. milk/urine in ketosis
-Neg. E balance (NEB) state: Incr. LL->Incr.FFA->B-ox. in liver. Incr. AcCoa
-Ketonaemia: incr. level of KB in blood
a) Prim.: high yielding cattle. Pregnancy toxicosis.
b) Sec.: fasting ketosis. Diabetes mellitus.
-Ketonuria: incr. level of KB in urine
KG and GG:
-Prod more KB than used.
-Cow-dairy ketosis/ewe-pregnancy toxaemia -> ketonemia + ketonuria happens
-Excess amount of AcCoA, because TCA is unable to ox. all AcCoA gener. from B-ox of FAs -> GNG use up OAC which is ess. for entry of AcCoA into TCA -> Liver will start prod. of KBin large amount, released in blood by kidney (prim. ketosis).
-Ru also capable for extrahepatic KG
1) Rumen mucosa: B-hydroxybutyrate
2) Mammary gl: acetoacetate
-Tissue/precursor/KB:
1.Liver – Free FAs – Acetoacetate
2.Mammary gl. – Acetate – Acetoacetate
3.Rumen mucosa – butyrate – B-hydroxybutyrate
Lipid metabolism:
-Low lipid diet (2-5&)
-Saturation in rumen
-microbial conjugated linoleid acid synt.

26

I. 26.Central role of the liver in the intermediary metabolism (Carbohydrate and lipid metabolism, metabolism of nitrogen-containing compounds) (Secretion activity of the liver)

-Composition: water (70-75%), protein (12-24%), lipid (2-6%), glycogen (2-8%)
-Central role: processes+distributes nutrients (because the serous drainage of gut passes through hepatic portal v. before general circ). Takes up carbs., lipids and most aa. during abs. period-the nutrients are then metabolized, stored or transp. to other tissues
Carbohydrate metabolism:
-Liver is norm. glu. prod., but after intake of feed containing carbs -> net consumer of glu.
-Elevated levels of IC glu in hepatocytes: glucokinase phosphorylate glu to glu-6-P, which is a central compound of carbs. metabolism
Aa. metabolsim:
-During abs.: liver takes up aa. which can be used locally as substrates of prot.form.
-After intake of prot.-rich food: more aa. present than liver can use in prot.synthesis – excess amount released into blood for all tissues to use in prot.synth./deamination
-NH3 dervied from cat. of aa. enters ura cycle -> urea form. in liver
-GNG occurs prim. in liver -> glucogenic aa. can serve as precursor of glu. synth.
Lipid metabolism:
-Plasma lipoprot. are predom. synth. in liver and intestine
-FAs can be metabolized in liver: B-ox. (major source of E in hepatic tissue)
-Prod. chol. In highest amount
-Synthesixe KB from Ac-CoA
Secretion of liver:
-Bile: continuously secreted by hepatocytes and transported though a sys. of ducts to gallbladder where it´s modified, conc. and stored. Major comp.: bile pigments+bile salts
-Bile pigments: biliverdin, bilirubin
-Bile salts: under norm. condit. only conjugated bile acids present in bile

27

I. 27. Detoxification activity of the liver (Different detoxification processes: synthesis, hydrolysis, oxidation, reduction, conjugation. Operation of cytochrome P450 enzyme system)

-Detoxif.R: biochem. changes in liver, converting foreign/toxic mol. to more readily excretable ones.
-Synthesis: detoxif. of NH3; converted to larger, not toxic compounds excreted w. urine. 1)Urea cycle in mammalian liver 2)uric acid cycle in avian liver
-Ox.: hydroxylations-conversion of ald.+acids.
a)Alpha-hydroxylation: E is mixed-function oxygenases, requires activ. of O2 by cytochrome P420 E.
-Cyt. P450 oxygenase sys.: major P for hydroxylation of aromatic+aliphatic comp. Detoxify drugs+foreign comp.
b)Metabolic activ. of ethanol: yields Ac-CoA by a P of 2 ox.R by E found in liver
-Red.: hydrolytic cleavage of ester, amide, glucoside linkages
-Conjugation: Most common is form. of an ester type of linkage w. glucuronic acid. Activ. from UDP-glucuronic acid. Compounds containing phenolic or alcoholic hydroxyl gr. are conjugated to form glucuronides.
-Sulphuric acid: used for detoxif. of compounds w. phenolic or alcoholif hydroxyl gr. Sulfates formed are secreted w. salts. Indole is ox. w. indoxyl -> conjugated w.H2SO4 to form indoxyl sulphuric acid

28

I. 28. Biochemistry of the muscles (Mechanism of muscle contraction. Metabolism of muscles, types of muscle fibres)
Biochemistry of adipose tissue, kidneys and brain.

Striated muscle:
-Red m.: sustained activity. Higher rate of O2 utilization.
*High myoglobin, low glycogen, many mitoch., aerobic matab., slow fatigue.
-White m.: larger high-E-P reserved, higher capacity to derive E from glycolytic Rs.
*Low myoglobin, high glycogen, few mitoch., anaerobic metab., quick fatigue
Muscle contraction:
-Myofibrils: 1)contractile (myosin, actin) 2)regulatory (tropomyosin, troponin)
-Myosin: 2xH-chains, 2xL-chains. When exposed to trypsin, peptide linkages near tail are cleaved to yield 1H and 1L fragment: H/L meromyosin
-L meromyosin: forms filaments. No ATPase activ. -> can´t combine w. actin
-H meromyosin: cat. hydrolysis of ATP+binds to actin. Can´t form filaments. Can be split into 2 globular fragments (S1) and 1 red-shaped fragment (S2). Each S1 contain ATPase active site+binding site for actin.
-Actin: G-actin (globular) and F-actin (fibrous). G-actin binds 1Ca2+ + 1ATP
Cardiac m.:
-Under norm. condit: high resp. activity. Uses mainly FAs instead of carbs. Under anaerobic/ischemic condit. E is derived from anaerobic GL -> lactic acid
-During starvation: cardiac glycogen level remains relatively stable
-More intensive aa metab. + rate of prot.synthesis
Muscle contraction:
1.AP trigger release of Ca2+ by SR
2.Ca2+ binds to troponin and causes conf. changes transmitted to tropomyosin and then actin
3.Tropomyosin moves from binding site of actin
4.S1-heads of myosin interact w.actin units and actomyosin complex is formed
-E-source: ATP and P-creatine. Red m.; mainly resp. White m.; mainly GL.
White adipose tissue: major E reservoir
-Cytoplasm is major site for accumulation of TAGs
-Specialized for synthesis+storage of TAGS and their mobilization into fuel mol.
Brown adipose tissue: intensive vascularization, dense mitoch. Prod heat instead of ATP.
Brain: glut-1,3-transported
-No significant stores of glycogen/TAGS
-For E: Substrates must cross the blood-brain barrier, by blood-glu
-FAs not fuel (bound to albumin)
-KB replace glu as fuel during starvation
Kidney: glutaminase activity (glu+H2O->glu+NH3)
-NH3 in acidic milieu->NH4->excreted by urine
-Glu uptake: need SGLT-1+2, GLUT-2
-Ps: GG, GGL, GL, GNG, KG, KL, FA-B-ox.

29

II. 1. Vitamins in general. Antivitamins. Vitamin antagonists.

Vit. in gen.:
-Organic nutrients
-Required only in small amounts
-Essential and necessary for normal maintenance, growth, reprod.
-Some can be synthetised from precursors or provitamins, e.g. B-carotene
-Fat-sol.vit.: lipids (insol. in water but extractable w. org.solv.). Derived from isoprenoid (vit. A, K, E). Vit.D from steroid derivate. Digested and absorbed w. fat in diet.
*Bile secretion by liver + lipase secr. by pancreas is vital to abs. of fat and fat-sol.vit.
*Abs. in small intestine to lymph.sys. or portal v.
-Water-sol.vit.: Vit.B + C. Main abs.sites is jejunum and ileum. In Ru B.vit.synth. in forestomachs, abs. in small intestine. Monogastric anim. has microbial synth. in colon+cecum.
*Excretion: prim. in urine
*Vit.B12: require intrinsic factor abs. in ileum, excreted in bile+urine
Antivit.: makes vit. ineffective. Similar structures as vit.
-Known for all vit. except A and D
-Pyrithiamine: competitively inhib. action of thiamine
-Dicumarol: nat. occurring, isolated from spoiled sweet clover hay
Vit.antagonist: specif. antagonize the bio. action of the vit. Diff. structures as vit.
-Avidin: heat-labile->changed/destroyed at high temp. In raw egg-white
-Thiaminase E: splits and activates thiamine. Destroyed by heat.
-Avitaminosis: condition induced by tot. abscense of a single vit. from the diet
-Hypovitaminosis: partial deficiency of a given vit.
-Hypervitaminosis: excess amount of a vit. (unlikely)

30

II. 2. Structure and metabolism of β-carotene and derivatives of retinol (vitamin A).

-Pathway(!)
-Provit. for vit.A (retinol, retinal, retinoic acid)
-Retinoic acid can´t substitute for retinol and retinal
-Both B-carotene and A.vit is destroyed when O2 is present
-Cattle abs. B-carotene, since there is no carotenase activ. in mucosal cells
1.Vit.A occur in feed as palmitate ester
2.Palmitate ester is hydrolysed in small int. by retinyl-ester hydrolase (pancreas)
3.Abs. as retinol by mucosal cells (vit.A norm. abs. as retinol)
4.Re-esterified to palmitate in mucosal cells
5.Excreted to lymph
6.Removed+stored by liver as palmitate
7.Released as retinol (hydrolysed) bound to RBP
8.Tissue cells containing cellular RBP carries retinol to sites in nucleus where they act as steroid hormones
9.Metabolized retinol, retinal+retinoic acid converted+excreted in bile

31

II. 3. Biochemical role and deficiency of retinol (vitamin A). Toxicity of vitamin A (hypervitaminosis)

Biochem.role:
1.Maintain epith.cells
2.Reprod. (stim spermatogenesis, inhib. fetal resorp.)
3.Bone growth (reg. osteoblast+osteoclast activity)
4.Visual cycle (rhodopsin)
Deficiency:
-Affect bone develop.+growth, reprod., vision
-Animals lose appetite because of keratinization of taste buds
-Slow bone growth->can´t keep pace w. CNS growth->CNS damage
-Night blindness-early sign
-Xerophtalmia: pathol. dryness of cornea+conjunctiva
-Deficiency if B-carotene in cattle->affects reprod.
Hypervitaminosis: toxicosis in farm animals
-Occur only after ingestion and injection of large doses (not B-carotene)
-Mostly young animals
-Symptoms: red. appetite, poor growth, loss of weight, bone fragility

32

II. 4. Structure and metabolism of calciferol (vitamin D). Conversion of provitamin to calciferol.

-Pathway(!)
-Steroid derivate
-Group of vit.-2 important; Vit D2 (ergocalciferol) and D3 (cholecalciferol)
Metabolism: two sources:
1.) diet: ergocalciferol present in sundried hay, cholecalciferol in animal tissues
2) endogenous vit. precursor: 7-dehydrocholesterol (converted to cholecalciferol in sun-exposed skin)
-Vit.D2+D3: bio. inactive->converted in vivo to active form by 2 hydroxylation R
-Regulation of 1-a-hydroxylase:
1) Direct: low plasma P incr. activity
2) Indirect: low plasma Ca incr. activity (triggers release of parathyroid hormone)
-Hypocalcaemia: elevates level of plasma 1,25-diOH D3

33

II. 5. Biochemical role and deficiency of calciferol (vitamin D). Toxicity of vitamin D (hypervitaminosis).

-Major function: maintain plasma Ca+P at a level which plasma is supersaturated w. respect to bone minerals, allowing calcification to proceed. Accomlished by:
1) Int.Ca+P abs.
2) Mobilization of Ca+P from bone
3) Renal reabs. of Ca+P
-1,25-diOH D3: acts at a cellular level on int. cells, renal tubular cells, osteoblasts
-Effect on int.:
1)promote movement of Ca from int.lumen to blood
2)1,25-diOH D3 initiates int.P-transport mechanism
-Effect on bone: incr. plasma Ca+P conc. by stim. metaboliz. of Ca+P from bone. Requires PTH+prot.synth.
-Effect on kidney: incr. reabs. of Ca+P
Deficiency:
1.Richets in young animals: continioud form. of collagen matrix, but incomplete mineralization in soft, pliable bones
2.Osteomalacia in adults: demineralization of pre-existing bones incr. their susceptibility to fracture
-In both cases: low plasma Ca+P level and incr. activity of alkaline phosphatase
-Low plasma Ca level: direct stimulus for parathyroid gl. to incr. the hormonal output
Hypervitaminosis: Vit.D is most toxic
-Can be stored in body + slowly metabolized
-Characteristics: Incr. Ca abs. + bone dissolution (incr. plasma levels of Ca -> calcification of diff. tissues -> fragile, deformed bones)

34

II. 6. Structure, metabolism and deficiency of tocoferol (vitamin E).

-Derived from parent compound: tocol
-Several nat. occurring tocopherols
-Alpha-tocopherol: widest nat. distribution+greatest bio.activity
-Very heat-stable in absence of O2
-Withstand acids at elevated temp
-Destroyed w. ultraviolet light + ox.
-Good antioxidants
-Ox. of a-tocopherol prod. a quinone derivate
Metabolism: vit.E ester of feed are hydrolysed prior to abs.
-Bile is essential for abs.
-Most enter blood circ. via lymph, where it´s associated w. chylomicrons+lipoprot.
-Storage: mainly in liver, also adipose tissue
-Excretion: mainly via bile, some water-sol. via urine
Deficiency:
-Prod. of auto-ox. (lipid peroxides) detected in adipose tissue of a-tocopherol-deficient animals, since it acts as an antioxidant
-Cause ultrastructural+biochem. changes in cellular membranes
-Sympt. in rats:
1)female: mild defic. may distrurb estrus cycle, stronger can cause death+resorption of foetuses 8-10d after conception
2)male: degeneration of germinal epith., testes w. complete sterility
-Sympt. in cattle+sheep: white muscle disease
-Sympt. in poultry:
*Chickens: encephalomalacia (cause loc. haemorrhage+neucrosis in cerebellum)
*absence of vit.E+selenium in diet: chicken develop exudative diathesis (incr. capillary permeability resulting in subcut.oedema)

35

II. 7. Biochemical role of tocoferol (vitamin E). Oxidative stress, free radicals, antioxidants.

-Strong antioxidant->prevent non-E ox. of polyunsat. FAs by molecular O2 and free radicals
-Peroxidation (auto-ox.) of lipids exposed to O2 responsible for: worsen the quality of feed+damage tissue. Initiated by free radicals.
-First line of defence against peroxidation of cellular+subcellular membr. lipids
*Acts as chain-breaking antioxidant and inhib. destructive peroxidation of polyunsat. FAs that are associated w. membr. lipids.
-Glutathione peroxidase: 2nd line of defence (cytoplasmic E, contain selenium, converts toxic peroxides into harmless)
-Prevent activ. of lysosomal E: protects organic mol., mainly tissue prot. from hydrolytic degradation
Antioxidants: vit.A, vit.E and vit.C

36

II. 8. Structure and metabolism of phylloquinon (vitamin K).

-Substituted napthoquinones
-Both vit.K1,K2 and K3 bio.active
-Vit.K1 (phylloquinone): 2-methyl-3-phytul-1,4-napthoquinone. Side-chain contains 20 C. Found in green plants.
-Vit.K2 (menaquinone): prod. of bact. synth. Contains side-chain w. diff. length. Original contain 6 isoprene units in side chain at 3rd position, others 7/9 isoprene units
-Vit.K3 (menadione): 2-methy-1,4-napthoquinone. No side chian. Chem. Synth. from the vit.
Matabolism:
-Abs. in small int.
-Bile salts: appear to have a direct role in the abs.
-Vit.K2 can be abs. from colon
-Side-chain of menadione formed in mitoch. of hepatic cells
-Not stored in signif. amounts->continuous intake necessary
-Excreted in urine as glucuronide/sulphate
-Animals can´t sunth. napthoquinone-ring, must be provided in diet. Bact.+plants can synth. from shikimic aicd

37

II. 9. Biochemical role and deficiency of phylloquinon (vitamin K)

Biochem.role:
-Required in hepatic synthesis of pro-thrombin and other blood-clotting factors
-Pro-thrombin are synth. as inactive precursor mol. Form. of active form requires vit.K dependent carboxylation of glutamic acid residues. It forms a mature clotting factor containing gamma-carboxy-glutamic acid. R. need vit.K, O2, CO2
Deficiency
-Decr. in blood plasma pro-thrombin conc. Severe def.: incr. blood-clotting time
-Young chicken: haemorrhage syndrome characterized by int. bleeding and long blood-clotting time.
-Other sp.: supplied w. vit.K2 from ruminal/intestinal bact. which synth. it.
-Can lead to deficiency:
*Monogastric animals kept on wire-bottom cages and then prevented from eating feces
*Minimalized growth of int.flora by oral drug administration
*Any influences that eliminate flow of bile into the int. (decr. abs.)
-Newborn: can develop alimentary vit.K deficiency since the vit. is not readily passed from mother to fetus + int. tract of newborns is sterile for the first days after birth.
-Hypovitaminosis in dogs can be prod. by surgical procedures that allow bile to drain through the ureter into urinary bladder
-Vit.K antagonists: dicumarol (in spoiled sweet clover hay), warfarin (rat poison)

38

II. 10. Biochemistry of essential fatty acids.

-2 unsat. FAs are essential in domestic animals: Linoleic (18:2) and linolenic aicd (18:3)
-Arachidonic acid (20:4) is essential is its precursor, Lineleic acid, is missing in diet.
Metabolism:
-Plants: can synth. linoleic and linolenic acid from oleic acid (animals can´t)
-Animals: can synth. arachidonic acid from linoleic acid
-Biochem. function: 1)required for prostaglandin synth. 2)required for membr. form.
-Prostaglandins: elicit wide range of physio. respons. Prod. in very small amounts. Differ from true hormones because they are formed in almost all tissues and act locally.
*Dietary precursor: linoleic acid
1) linoleic a. is first converted to 20-C polyunsat. FA, mainly arachidonic a.
2) ox.+cyclization of arachidonic a. into prostaglandins
-Membr.form: unrelated to prostaglandin synth. Found in struct. lipids of cell. Present in phospholipids.
Deficiency: rare because they are widely distributed in nature. Not seen in adult animals
*Young animals: diet w. low fat content develop scaly dermatitis+hair loss

39

II. 11. Structure and metabolism of thiamine (vitamin B1).

-Consists of: substituted pyrimidine ring, substituted thiazole ring, methylene bridge (link the 2 rings) and pos. charged N in the thiazole ring.
-Nat. occurring mol. and synthetic vitamin. Contains: 1) HCl on the amino gr. 2) Cl- neutralizing the pos. charge on the N
-Destroyed at elevated temp. unless pH is low
-In alkaline sol.: thiochrome is formed under controlled conditions
Metabolism:
-Animals require thiamine in diet, except Ru; their bact. provide the vit.
-Abs. of dietary thiamine: mainly duodenum and prox. jejunum
-The abs. thiamine is transported to liver where it´s phosphorylated by means of ATP to form the coE thiamine pyrophosphate (TPP)
* Thiamine+ATP –(thiamine kinase (need Mg2+)->TPP+AMP
-Storage: in very limited amounts, except swine (muscle is rich in thiamine)
-Excretion: the vit. + it´s metabolites are excreted in urine

40

II. 12. Biochemical role and deficiency of thiamine (vitamin B1)

-TPP: cofactor in ox. decarboxylation of alpha-keto acids: 2 a-keto acids, pyruvate and a-ketoglutarate are ox.decarboxylated
-In mitoch. Matrix
-Both multi-E complexes need 5 cofactors that acts as carriers or oxidants for the intermediates of the R: TPP, NAD+, FAD, HS-CoA, lipoic acid
-TPP: cofactor in non-ox. R of PPP: ribose-5-P is converted to intermediates of GL
-TPP is only cofactor needed: prosthetic gr. of transketolase
Deficiency:
-Low thiamine intake develop def. symptoms
-Impaired cellular function due to decr. activity of the DH R: mainly NS, where carbs are the predominant ox. substrates
-Elevated blood pyruvate levels
-In human: Bero-Beri disease: in areas where polished rice is the main source of E
1) Dry Beri-Beri: muscular weakness, loss of weight, neuritis, evidence of involvement of CNS
2) Wet Beri-Beri: oedema, impaired cardiac function
-In poultry: impairement of NS: lameness, convulsions, retraction of head
-Thiaminase: destroy the vit. by splitting it at the methylene bridge prod. free pyrimidine and thiazole components.
*Found in some raw fish used in diet of fur-bearing animals (affect: chastek´s paralysis, head pulled back)
*Some rumen-bact. also prod. thiaminase. Cattle, sheep: cerebrocortical necrosis
-Ingestion of synthetic antivit.: pyrithiamine (pyridine ring instead of thiazole ring). Reversible when sufficient amount of extra thiamine is induced in diet.

41

II. 13. Structure and metabolism of riboflavin (vitamin B2)

-Consists of D-ribitol attached to 6,7-dimethyl-isoalloxazine
-Water sol. to a limitied degree
-Yellow water-sol.
-Intense green fluoresence
-Reversibly red. by several agents to leucoriboflavin
-In gen. both acid- and alkali-stable
Metabolism:
-Dietary riboflavin is phosphorylated in the int. mucosa, liver + other organs into bio. active forms: flavin mononucleotide (FMN), flavin adenine dinucleotide (FAD)
1) Riboflavin+ATP-(flavo-kinase, Mg2+)->FMN+ADP
2) FMN+ATP-(Falvin nucleotide phosphorylase, Mg2+)->FAD+PP
-Liver, kidney: may contain great amount of the vit., mainly in phosphorylated form
-Excretion: in urine, milk (contain the free vit.)
-Microbial synth. of riboflavin: rumen, gut

42

II. 14. Biochemical role and deficiency of riboflavin (vitamin B2)

-FMN-FAD=prosthetic gr. for flavoE (flavoprot.)
-The prosthetic gr. are covalently linked to the apoE through the methyl gr. in the isoalloxazine ring
-The prosthetic gr. are usually only sep. from the apoE after acid treatment
-Both flavin nucleotides are capable of reversibly binding 2 H to the isoalloxazine ring: FMNH2, FADH2
-Flavoprot. can be classified into:
1) Aerobic DH: the red. form can react directly w. mol. O2 to form H2O2 which is decomposed to H2O and O2 by catalase. E.g.:
a) FAD-dependent D-amino acid oxidase: cat. the ox.deamination of the un-nat. D-isomers of aa.
b)FAD-containting xanthine oxidase: converts hypoxanthine to xanthine-> to uric acid
2) Anaerobic DH: the E usually also contains a metal ion. Most important:
a) FMN-linked NADH DH: member of resp.chain acting as a carrier of e- from NADH to the more elctropos. components
b) Succinate DH: E of TCA. Contain covalently bound FAD+iron sulphur prot.
c) Fatty acyl CoA DH: contain FAD. Cat. the first DH-step in the beta-ox. of FAs
Deficinecy:
-Not associated w. major diseases
-Frequently accompanies other vit.B def.
-In adult Ru: no def. symptoms occur under norm. cond.; synth. in ruminal microbes
-Leas to impairment of many metabolic processes
-Gen. symptoms: poor growth, dermatitis, loss of hair, eye changes incl. keratitis
-Young poultry: leg paralysis
-Laying hens: red. egg prod. + hatching-ability

43

II. 15. Structure and metabolism of niacinamide (vitamin B3).

-Nicotinic acid: substituted pyridine derivate -> pyridine 3-carboxylic acid
-Nicotinamide: amide instead of carboxyl gr.
-Both have vitamin activity, but nicotinamide is the active form in the organism
-Nicotinic acid: prod. by ox. of nicotine w. strong ox.agents. Only 1% water-sol, but sol. in alkaline sol.
Metabolism:
-Feed containing pyridine nucleotide derivatives are broken down in the digestive tract to give nicotinic acid
-Nicotinic acid is abs. into circ. and transported to liver via portal v.
-Liver: nicotinic acid/nicotinamide converted to NAD+ in several steps (need PRPP+ATP)
-NAD+ is phosphorylated into NADP+ by NAD+ kinase
-Nicotinic acid can also be synth. from tryptophan in liver: other B-vit. is needed. Inefficient (only 1 mg is formed from 60 mg tryptophan). Only when there is great amount of the aa.
-NAD+ is converted into nicotinamide + ADP-ribose by NAD+-ase
-Nicotinamide deaminase R occur in liver: nicotinamide+H2O->nicotinic acid-NH3
-Nicotinic acid: not stored in organism
-Excretion in Ru: unchanged, in urine
-Excretion in monogastric sp.: methylated, in urine (methylation occur In liver, forming N-methylnicotinic acid)

44

II. 16. Biochemical role and deficiency of niacinamide (vitamin B3)

-Bio. active cofactor forms of the vit.: NAD+ and NADP+
-Both found in all cell types
-NAD+ is usually present in much greater amount than NADP+
-In liver cells: ca. 60% of NAD+ found in mitoch., rest in extramitoch. Cytoplasm
-NADP+ more in cytoplasm than mitoch.
-Both serve as coE in redox-R where the coE undergoes red. of the pyridine ring by acceptin a H+ + 2e-
-DH of NAD+: only H of substrate is directly transferred to NAD+, the other appears in the solvent
-Most of pyridine-linked DH are specific for either NAD+ or NADP+, except L-glutamate DH which can react w. both
-P requiring the ox. or red. form of NAD+: GL, TCA, GNG, FA degradation, KG, ethanol degradation
-P requiring the ox. or red. form of NADP+: PPP, FA synth., cholesterol synth.
Deficiency:
-Human: pellagra (corn=large part of diet): low tryptophan content of corn prot. Dermatitis, diarrhea, dermentia
-Dogs: black tongue syndrome (=pellagra): necrotic lesions of tongue+buccal mucosa, intense salivation, diarrhea, death
-Pigs: loss of appetite, dermatitis, degenerative changes in int.mucosa, diarrhea
-Young chicks, goslings, ducklings: appetite loss, poor growth, slow feather development, perosis

45

II. 17. Structure and metabolism of pantothenic acid (vitamin B5), synthesis of HS~CoA.

-Consist of: alpha, gamma-dihydroxy-beta,beta-dimethylbutyric acid, joined to beta-alanine
-Free acid: viscous, yellow oil, soluble in water, ethylacetate
-Easily broken down by acidic or alkaline sol., heat
-Commercially prod.: synthetic white Ca-salt, Ca pentothenate
Metabolism:
-Abs. in int.
-Excretion: pantothenic acid not degraded before it´s excreted. 60-70% in urine, 30-40% in feces
-Flashcard for synthesis-pathway(!)

46

II. 18. Biochemical role and deficiency of pantothenic acid (vitamin B5).

-Biochem. role: pantothenic acid is component of
1)CoA: (nucleotide) cysteamine, pantothenic acid, 2+P gr., ribose-3-P, adenine
-Present in almost all tissues and organs: thickest conc. in liver, adrenal gl., heart, kidneys
-Free/red. form: HS-CoA
-Thiol gr.: acts as carrier of acyl-gr. forming activated thiolesters
-Acyl-sulphur bond: high-E bond
-Acetyl CoA, succinyl CoA, fatty acyl CoA, methylmalonyl CoA
2)FA synthetase complex: multiE complex, consist of 6E prot. and ACP
-Can serve as a acyl carrier through thioester. Form. w. it´s thiol gr.
-Carrier acetyl and acyl units during FA synth.
Deficiency:
-Rare, because the vit. is supplied in nearly all feeds + synth. by microorg. in rumen+int.
-Rats: lesions of adrenal cortex; CoA content red. w. 30-40%
-Black rats: loss of hair color (restored by a diet rich in pantothenic acid)
-Young chicks, turkeys: dermatitis (chicken pellagra), lesions around eyes, sealing of eyelids, retarded´rough feathering. Others: retarded growth, fatty degeneration of liver, red. hatchability
-Pigs: slowly growth, locomotor distrubances (goose stepping), sometimes paralysis of the HL
-Dogs: fatty liver, nervous symptoms (convulsions), GI tract disorders (diarrhea)

47

II. 19. Structure and metabolism of pyridoxine (vitamin B6).

-Vit.B6: collective term for pyridoxine, pyridoxal, pyridoxamine
-Derivatives of pyridine
-Differ only in the funct.gr. attached to the ring
-Func.gr.: -CH2OH (pyridoxine), -CHO (pyridoxal), -CH2NH2 (pyridoxamine)
-Sol. in water, slightly in ethanol
-Stable in dry heat, not in moist heat
-Synthetic form: pyridoxine hydrochloride (used in nutrient supplements)
Metabolism:
-Pyrodoxine: main form in neutral feeds
-Abs. into portal v.
-Transported to the liver
-Liver: converted into it´s active form
1) Oc. By NADP+-dependent pyridoxine DHs
2) In presence of ATP, pyridoxal kinase phosphorylates pyridoxal into the active coE form pyridoxal P (PALP)
-The various forms of vit.B6 are interconvertible, which is why pyridoxal and PALP can be prod. from the conversion of pyridoxamine
-Final elimination prod.: the bio. inactive pyridoxic acid, excreted in urine
-Storage: only small amount
-Microflora of rumen, colon: able to synth. the vit.

48

II. 20. Biochemical role and deficiency of pyridoxine (vitamin B6)

-PALP: coE for large nr. of E, especially those that cat. reactions involving aa.:
1)Transamination: all require PALP. Transaminases transfer the amino gr. of an aa. to the coE to generate pyridoxamine P, which then reacts w. an a-keto acid to form an aa. and regenerates the original aldehyde form of PALP
2)Decarboxylation: the non-ox. R of aa. also involve PALP as coE. Function of decarboxylases: prod. of bio. active amines.
3)Condensation: PALP participates in the biosynth. of porphyrins as coE of delta-aminolevulinic acid synthetase. All C-atoms of porphyrine is provided by glycine+succinyl CoA -> condense to form delta-aminolevulinic acid
*PALP involved in conversion of tryptophan to nicotinic acid
Deficiency:
-May be provided experimentally by feeding with the structural analog, 4-deoxypyridoxine
-Isoniazid (drug used to treat tuberculosis) can induce vit.B6 def. by forming an inactive derivative w. PALP
-Growth, reprod., function of NS, hematopoiesis, etc. are seriously affected
-Gen. symptoms: convulsions, loss of apetite, anemia, retarded growth, decreased feed utilization, dermatitis
-Epileptiform-type seizures: believed to be due to decreased decarboxylase activity -> leading to decr. of GABA levels in brain

49

II. 21. Structure, metabolism, biochemical role and deficiency of biotine (vitamin H).

-Cyclic compound: fusion of an imidazole ring w. a tetrahydrotiophene ring w. acid side chain
-Free biotin: soluble in dilute alkali+hot water. Slightly in dilute acid, cold water and alcohol
-Dry, crystalline biotin: fairly stable to air, daylight and heat
-Gradually destroyed by UV radiation
Metabolism:
-Abs. as an intact molecule in small int.
-Biotin plasma conc.: linearly related to biotin intake
-No detailed info. on how biotin is catabolized: undergoes some metabolic changes, involving ox. of the side chain, the ring is not broken -> not able to degrade it
-Excretion: mainly urine
-Biochem.role: prosthetic gr. in many E. Covalently bound to gamma-amino gr. of lysine residue of the biotin-dependent apoE.
-Biocytin: carboxyl gr. of biotin linked to the gamma-amino gr. of lysine
-Covalently attached to the apoE through a peptide linkage w. lysine residue at the active site
-Act´s as prosthetic gr. in carboxylation Rs->carrier of activated CO2
1) First step in FA synth=carboxylation of AcCoA, cat. by AcCoA carboxylase (cytoplasm of adipose cells)
2a) A key R in GNG cat. by pyruvate carboxylase (E-location: mitoch., hepatocytes, kidney cells, not m. cells)
2b) Biotin is the prosthetic gr. of propionyl CoA carboxylase, which prod. methylmalonyl CoA (E-location: mitoch., hepatocytes)
Deficiency:
-Rare, since the vit. is widely distributed in diff. feeds + ruminal/int. bact. supply
-Not observed in adult Ru
-Easily induced in most animals by inclusion of raw egg white in diet – contains Avidin
-Avidin: binds biotin and prevents its abs. from int.
-Rats: dermatitis around the eyes, Alopecia (spot baldness), weight loss, death
-Poultry, swine: observed on a biotin-def. diet without avidin
-Young chicks, turkey: specific dermatitis, lesions on beak, eyelids, toes, shanks, poor feather development
-Laying hens: red. egg. prod.+hatchability, fatty liver
-Pigs: scalness, rough hair coat, loss of hair, cracks in the feet

50

II. 22. Structure and metabolism of folic acid (vitamin B9)

-Consists of substituted pteridine ring, p-amino benzoic acid, glutamic acid
-Pteridine moiety is linked through a methylene gr. at the 6th position to the p-aminobenzoylglutamate
-Several forms of folic acid: pteroylpolyglutamic acid derivatives
-Yellow colour
-Slightly water sol. in acid form, water sol. salt form
Metabolism:
-Dietary forms: usually polyglutamate derivatives
-Abs.: polyglutamate need to be hydrolysed into monoglutamate prior to the transport across the int. mucosa (cat. by pteroylpolyglutamate hydrolase)
-Circ. form: monoglutamate derivatives
-In tissue: predominantly polyglutamate derivatives
-Under norm.cond.: over 50% of the vit. is stored in the liver
-Folic acid: no coE activity
-Converted by a 2-step red. to it´s active form, tetrahydrofolic acid (FH4). Terminal step is red. of dihydrofolic acid, cat. by FH2 reductase)
1) Folic acid+NAPDH+H+->FH2+NADP+
2) FH2+NADPH+H+-(FH4 reductase)->FH4.+NADP+
-Excretion: urine (small amount, feces (great amount)

51

II. 23. Biochemical role and deficiency of folic acid (vitamin B9)

-Metabolic role of folic acid coE: acceptor/donor of one-C fragments
-One-C fragments: bonded to N-5 or N-10 or both of the folic acid coE
-Most important one-C fragment-FH4 compounds: N^5N^10-methylene-FH4, N^5-formyl-FH4, N^10-formyl-FH4
-Serve as donors of one-C units in variety of biosynthesis:
1)Some of the C of purines are derived from the N10-formyl-FH4. Methyl gr. of thymine from N5, N10-methylene-FH4
2)Synth. of aa:
Deficiency:
-Animals unable to synth. a pteridine ring – from diet/microorg. In GI tract
-Young chickens, turkeys: hypovitaminosis easily induced by low folic acid intake
-Pigs: don’t develop folic acid deficiency symptoms, unless sulphonamides are added to diet->analogs of p-aminobenzoic acid->competitively inhib. the microbial synth.
-Other domestic animals: less susceptible to hypovitaminosis->def. sympt. can be provoked by using several drugs: aminopterin+amethopterin->analogs to FH2->competitive inhib of FH2 reductase
-The analogs can prevent normal synthesis of FH4 coE (anti-folic acid agents)
-Most important gen. def. sympt.: anemia, red. growth rate
*depressed synth. of purines and thymine inhib. growth, especially m. growth
*anemia: result of diminished DNA synth. that requires FH4 derivatives

52

II. 24. Structure and metabolism of cobalamin (vitamin B12)

-Contains a corrin ring sys. having 4 pyrrole units
-2 of them (ring A+D) are directly bonded to each other, the others by methylene bridges
-Substituents on pyrrole rings: methyl, proprionamide, acetamide gr.
-Cobalt: held in centre of corrin ring by 4 coordinate bonds from N of pyrrole gr.
-5th sub: derivative of 5,6-dimethylbenzimidazole containing ribose-5-P+1-amino-2-propanol
-Cyanocobalamin: red., needle-like, hydroscopic crystals
Metabolism:
-Obtain vit. from their neutral bact. flora or by eating feeds derived from other animals
-Abs.: require intrinsic factor (glycoprot.)
1. Intrinsic factor binds cobalamin in int. lumen
2. Complex binds to ileal receptor
3. Complex dissociates
4. Vit. actively transported into bloodstream
-Cobalamin in plasma: most attached to specific proteins
-Most occur as 2 coE-atically active forms: 5-deoxyadenosylcobalamin, methylcobalamin
-Stored in liver in great amount
-Excretion: urine, bile, feces.
-60-70% is reabsorbed in ilium by means of intrinsic factor mechanism

53

II. 25. Biochemical role and deficiency of cobalamin (vitamin B12)

1) Rs requiring DA-cobalamin: all except one of the R can be classified as rearrangement Rs
-Exception: red. of ribonucleotide to deoxyribonucleotide
-Most important intramolecular rearrangement: form. of Succinyl-CoA from methylmalonyl CoA: the –CO-S-CoA gr. migrates from C2 to C3 in exchange for a H-atom
-Ribonucleotide red.: the 2´-hydroxyl gr. is replaced by H. Provides building block for synth. of DNA.
2) Rs requiring methylcobalamin: the synth. of methionine from homocysteine (can accept a methyl gr. from N5-methyl-FH4 and methionine is formed cat. by homocysteine methyl transferase) + B9/folic acid as methyl gr. donor
Deficiency:
-Human: in patients who fail to abs. the vit. from int..
*Due to failure of the parietal cells of stomach to secrete intrinsic factor. B12 is not abs.=pernicious anemia.
*The erythropoietic tissue of BM needs DA-cobalamin for DNA synth. Def. leads to megaloblastic anemia
-Farm animals: mild anemia can be observed. Other sympt: red. appetite, red. growth, impaired feed utilization, neurological disorders, reprod. Failure
-Ru: usually indirect and related to a dietary shortage of cobalt (in centre of B12)
-Vit.B12: only synth. by microorg., not present in plants
-Herbivores: vit. prod. by ruminal or int. flora+by coprophagy
-Ca: int. synth. not sufficient, dietary cobalamin needed

54

II. 26. Structure, synthesis and metabolism of ascorbic acid (vitamin C)

-Flashcard for pathway (!)
-L-ascorbic acid: one of the most imp. sugar acids
-Gamma-lactone of 2-keto-L-gluconic acid, having an enediol structure at C2+C3
-Very unstable->ox. to dehydro-L-ascorbic a.
-Redox sys. bw. ascorbic a. and dehydro ascorbic a. (both bio. active)
-Ox. of dehydro-ascorbic a.: prod. diketogulonic a. (inactive), due to heat, light
-Ox. of dehydro-ascorbic a by molecular O2 is cat. by cupric+siwer ions
-When lactone ring has opened: further ox. of the mol. -> may be degraded to oxalic acid
Metabolism:
-Synth. in plants+almost all mammals+birds, except human, monkey and guinea pig
-Prod. in liver by animals who can synth. it
-Birds: liver+kidney
-Precursor: free D-glucuronic acid
-Abs.: 1)human, guinea pig: great amount in small int. 2)others: simple diffusion from int.
-Ox. of ascorbic acid to dehydro-ascorbic acid occur in kidney
-In blood plasma: vit.C usually present in red. form
-Highest conc. in glandular tissues: pituitary gl., adrenal fl., corpus luteum
-Excretion: urine as dehydro-ascorbic acid and oxalic acid
-Microorg.: unable to synth.

55

II. 27. Biochemical role and deficiency of ascorbic acid (vitamin C)

-Flashcard for pathway (!)
-Effective red. agent: 1)essential to many hydroxylation proc. 2)facilitates abs. of iron by red. it to Fe2+ in stomach
1a)Collagen synth.: Enzymatic hydroxylation of proline and lysine to form hydroxyproline and hydroxyproline (???). Need molecular O2+ascorbic acid
1b)Steroid hormone synth.: mitoch. and microsomal steroid hydroxylases in adrenal gl. account for the form. of corticosteroid
1c)Serotonin synth.: tryptophan is first hydroxylated to 5-hydroxy-tryptophan, in presence of ascorbic acid. Serotonin is then formed through decarboxylation.
1d)Tyrosine degradation: 2 mixed-function oxidases, dependent on vit.C. Occurs largely in CNS.
2)Iron abs. as Fe2+ from duodenum: must be red. by ascorbic acid from Fe3+ before abs.
Deficiency:
-Human: scurvy disease (capillary fragility, widespread hemorrhages, swollen+bleeding gums, teeth loosening, weak bones, anemia. Def. in hydroxulation of collagen: defective CT
-Farm animals: only mild def. sympt. can be seen; weakness, fatigue, dyspnoea
-Swine, poultry: during heat stress

56

II. 28. Biochemistry of lipotropic factors (choline, inositol)

Choline: Beta-hydroxyethyltrimethyl-ammoniumhydroxyde
-Strong quaternary base
-Sol. in water+alcohol. Insol. in ether, chloroform
Metabolism:
-Ingestion: mainly in form of lecithin, less than 10% as free base/sphingomyelin
-Microorg. unable to synth.
-Obtained from diet+catabolism of membr. phospholipids+liver (de novo synth.)
-Synth.:
1)Ethanolamine form. from serine by decarboxylation
2)Ethanolamine converted to choline by 3 methylations (methyl donor: 5-adenosylmethionine)
-Storage: as lecithin and sphingomyelin in liver, kidney, brain
Biochem.role:
1)Form. of lecithin and sphingomyelin from choline
2)Physiological precursor of acetylcholine
3)Lipotropic agent: accelerates the rate of fat removal from liver
4)Source of labile methyl gr. for transmethylation Rs
Deficiency: fatty liver. Prolonged def.: cirrhosis (chronic liver disease). Haemorrhagic kidney degeneration. Highest importance in poultry+swine.
Inositol: derivative of cyclohexane: on H to each C is replaced by a hydroxyl gr.
-9 possible isomeric inositols, only one w. bio. activity: myo-inositol
-Metabolism: occur in nature or combined forms
-Phytin: Ca- and Mg-salts of inositol and hexaphosphoric acid
-Phytase: E capable of hydroyzing phytin
-Liver, kidney of young animals able to convert glu into inositol
-Ruminal+int.flora can prod. inositol
Biochem.role: not considered a vit. in humans+domestic animals, synth. endogenously in large animals+have no cofactor function
-Essential for certain sp., like fish
-Lipotropic sub. under special conditions
-Phospholipid component of membranes
-Phosphorylation of membrane-bound phosphatidyl-inositol occur in response to binding of diff. hormones, neutrotransmitters, growth factors on the receptor of cell membr.
Deficiency:
-Not been reported in farm animals
-Experimentally conditions, rats: growth failure, fatty liver, alopecia (spot baldness)