Final - oral Flashcards
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.
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.
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
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.
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.
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
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)
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)
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.
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)
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
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.
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+
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
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
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
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.
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.
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
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
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
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.
