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MADE FROM FATTY ACIDS
TAGs ARE BROKEN DOWN INTO MAGs IN SMALL INTESTINE AND FORMED INTO MICELLES
MICELLES ABSORBED BY INTESTINAL CELLS AND MAGs CONVERTED (USING LONG/VERY LONG FATTY ACID CHAINS BACK INTO TAGs
TAGs PACKED WITH OTHER LIPIDS INTO CHYLOMICRONS AND RELEASED THROUGH LYMPH INTO BLOODSTREAM
ACTION OF LIPASES
BREAKS DOWN TAGs INTO FATTY ACIDS, MAGs AND DAGs
HELPS CONVERT FAT DROPS INTO SMALLER EMULSION DROPLETS THAT HAVE HIGHER SURFACE/VOLUME RATION
Pancreatic lipase: Triacylglycerol Monoacylglycerol + 2 Fatty acids
Chylomicrons are secreted into the lymph and eventually reached the blood, where they are attacked by lipoprotein lipase. This enzyme attacks the triacylglycerols to release fatty acids and glycerol. Fatty acids are carried by serum albumin to adipose and other tissues.
STRUCTURE OF PALMITIC ACID
Know how triacylglycerols are broken down in adipose cells
The enzyme triacylglycerol lipase (also known as hormone-sensitive lipase) converts triacylglycerols into diacylglycerols by removing a fatty acid.
Other lipases break down the diacylglycerol into glycerol and three fatty acids.
Regulation of triacylglycerol lipase: This enzyme is activated by adrenaline, glucagon, and adrenocorticotropic hormone (ACTH). The enzyme is inhibited by insulin. In activation, the lipase is phosphorylated
Rationale: Adrenaline and ACTH promote response to stress. To cope with stress we need excess energy, hence, we need to break down fatty acids. Glucagon's role is to increase glucose levels in the blood. If we break down more fatty acids for energy, we will break down less glucose and, hence, glucose levels will be elevated.
HOW ARE FATTY ACIDS TRANSPORTED IN THE BLOOD?
Because of their insolubility, most lipids need to be transported in the blood in a complex with particular proteins.
Free fatty acids are transported by serum albumin
TAGs from the intestine are transported on chylomicrons.
TAGs made in the liver are transported on very-low-density lipoproteins (VLDL).
HOW ARE FATTY ACIDS TRANSPORTED INTO MITOCHONDRIA?
Straight-chain fatty acids (saturated and unsaturated) longer than 10 carbons are transported into mitochondria for degradation.
The fatty acid is carried across the mitochondrial membrane bound to carnitine.
carnitine is a metabolite of the amino acid lysine.
STEPS OF B-OXIDATION IN IN MITOCHONDRIA
Stage 1. Oxidation by Acyl CoA Dehydrogenase to Give Enoyl CoA. LCAD > 12 Cs, MCAD 6-12 Cs, SCAD 4-6 Cs
Stage 2. Hydration of the trans Double Bond by Enoyl CoA Hydratase to Give L-3-Hydroxyacyl CoA
Stage 3. Oxidation by L-3-Hydroxyacyl Dehydrogenase to Give Ketoacyl CoA. This reaction converts the hydroxyl group to a ketone
Stage 4. Cleavage by Thiolase. Product of this step is acetyl CoA. Fatty acid is now 2 carbons shorter. The cycle will continue, releasing 2 carbons per cycle until the last cycle yields two acetyl CoA molecules:
Energy yield of fatty acid β-oxidation
16-carbon palmitic acid MAKES 8 acetyl CoA, 7 of FADH2 and 7 of NADH.
2.5 ATP's per NADH and 1.5 ATP's per FADH2 and processing of acetyl CoA via TCA MAKES 10 ATP's per acetyl CoA
7 x 1.5 + 7 x 2.5 + 8 x 10 = 10.5 + 17.5 + 80 = 108
Recalling that we used up 2 ATP equivalents in the initial activation reaction, the net yield of ATP for the β-oxidation of one molecule of palmitate is 106 ATP's.
WHY ARE FATS MORE FATTENING THAN CARBS?
Compare this with glucose, where we get about 30 ATP's per glucose.
Glucose and palmitic acid have molecular weights of 180 and 256, respectively.
(106/256)/(30/180) = 0.414/0.167 = 2.48
Therefore, per unit weight, fats are more fattening than carbohydrates.
WHERE ARE very long-chain fatty acids degraded? WHAT IS BYPRODUCT?
Degraded in peroxisomes
H2O2 is a by-product
PATHWAY FOR KETOGENESIS
Step 1: Thiolase (an isozyme of the thiolase involved in β-oxidation) turns acetyl CoA into acetoacetyl CoA
Step 2: Hydroxymethylglutaryl CoA synthase reacts acetoacetyl CoA with acetyl CoA to form 3-hydroxy-3-methylglutaryl CoA
Step 3: Hydroxymethylglutaryl CoA lyase breaks down 3-hydroxy-3-methylglutaryl CoA into acetoacetate and acetyl CoA
Step 4: 3-Hydroxybutyrate dehydrogenase converts acetoacetate into D-3-hydroxybutyrate
Acetoacetate and D-3-hydroxybutyrate can freely diffuse out of the liver mitochondria and into the blood
ROLE OF KETOGENESIS
WHEN oxaloacetate supplies are low and yet fatty acid oxidation is proceeding rapidly.
Cause a build-up of acetyl CoA, which cannot easily be transported between tissues
Cells cope by USING ketogenesis, turns acetyl CoA into a readily water soluble and transportable form.
The four enzymes in this pathway are located in the mitochondria. The products and intermediates in ketogenesis are referred to as ketone bodies
USE OF KETONES
Certain tissues, such as cardiac muscle and the renal cortex prefer to use ketone bodies as fuel instead of glucose.
Important during exercisE AND starvation when glucose is not available
brain switches over to using ketone bodes BY convertING D-3-hydroxybutyrate into acetoacetate USING 3-hydroxybutyrate dehydrogenase
In uncontrolled diabetes and in starvation, supply of glucose inside cells is exhausted.
There is little oxaloacetate with which acetyl CoA can react. As acetyl CoA builds up, ketogenesis turns the acetyl CoA into ketone bodies.
Increased concentration of the acidic ketone bodies in the blood lowers the blood pH in a condition known as ketoacidosis.
The decreased pH can cause a coma
Role and regulation of acetyl CoA carboxylase in fatty acid synthesis
Fatty acids synthesized in the cytosol
The pathway not just the reverse of fatty acid degradation, but there are some interesting parallels between the two pathways
Two enzymes synthesize palmitate (16-carbons) from acetyl CoA (acetyl CoA Carboxylase and Fatty Acid Synthase)
For Acetyl CoA Carboxylase, a carboxyl group is added to acetyl CoA to generate Malonyl CoA.
biotin-containing enzyme catalyzes the committed step in fatty acid biosynthesis
subject to complex regulation
SERIES OF REACTIONS CATALYZED BY FATTY ACID SYNTHASE (7)
- 1. Acetyl Transacylase. Transfers the acetyl group from acetyl CoA to ACYL CARRIER PROTEIN (ACP)
2. Malonyl Transacylase. Transfers the malonyl group from malonyl CoA to ACP
- 3. Acyl-malonyl ACP Condensing Enzyme. Reacts a malonyl ACP with the acetyl ACP. One ACP is discarded as is a CO2; this creates a 4-carbon acetoacetyl group
4. β-Ketoacyl ACP Reductase. Uses NADPH to reduce the ketone to a hydroxyl group
5. 3-Hydroxyacyl ACP Dehydratase. Removes a water
6. Enoyl ACP Reductase. Reduces the double bond to give the 4-carbon fatty acyl butyryl ACP
The elongation process will then resume at step 3. At the end of each cycle of elongation the fatty acid is 2 carbons longer
7. Thioesterase. When the fatty acyl group is 16 carbons long, this enzyme cleaves it to generate free palmitic acid and ACP
COMPARISON OF FATTY ACID SYNTHESIS VS. B-OXIDATION
REGULATION OF ACYTYL CoA CARBOXYLASE
Citrate stimulates allosterically AND INACTIVATES by phosphorylation.
Phosphorylation catalyzed by AMP-activated protein kinase (AMPK).
AMPK is activated by AMP and inhibited by ATP.
Dephosphorylated by protein phosphatase 2A, WHICH IS in turn is inhibited by phosphorylation by protein kinase A. INSULIN ACTIVATES PROTEIN PHOSPHATASE 2A
PKA is activated by adrenalin and glucagon.
STRUCTURE OF FATTY ACID SYNTHASE
Three polypeptide chains, two of which are identical to each other.
The third is a very small polypeptide called acyl carrier protein (ACP), which contains a phosphopantetheine group that is identical to the one in Coenzyme A.
The other two polypeptides have 7 different enzymatic activities. First mobilizing malonyl CoA and acetyl CoA (attaching them to ACP). Then begins a cycle of reactions in which a fatty acid grows from ACP.
At the end of each cycle the growing fatty acid is 2 carbons long. When the fatty acid has reached 16 carbons in length, it is cleaved from the ACP.
SYNTHESIS OF LONGER-CHAIN FATTY
The mitochondria and the endoplasmic reticulum are the sites where we make fatty acids longer than 16 carbons
- A single cycle of four different enzymes (analogous to the ones in fatty acid degradation) uses acetyl CoA to convert palmitoyl CoA to the 18-carbon stearoyl CoA.
NADH and NADPH are used as reductants.
- 2. Endoplasmic Reticulum (general)
- A single cycle of four different enzymes uses malonyl CoA to convert palmitoyl CoA to stearoyl CoA.
NADPH is the reductant.
- 3. Endoplasmic Reticulum (brain)
- Four different enzymes similar to those in other tissues, acting in multiple cycles, use malonyl CoA to convert palmitoyl CoA to longer-chain fatty acids, up to 24 carbons long.
Patients with this disease lack peroxisomes. They are unable to metabolize, not only fatty acids, but other lipids as well (e.g. plasmalogens).
They suffer severe abnormalities of bones, cartilage, brain, liver and other organs. They generally do not survive beyond 6 months of age
Generally due to a mutation in the very-long-chain acyl CoA dehydrogenase.
Boys who have this disease are generally normal for the first 4-8 years of life. Then they exhibit neurological symptoms that gradually progress to a vegetative state.
They have an accumulation of very long chain fatty acids, particularly hexacosanoic acid (26 carbons). There is no real cure.
There is some evidence that when patients known to have the biochemical lesion but who have not yet developed neurological symptoms are treated with a mixture of glyceryl trioleate and glyceryl trierucate, development of symptoms can be slowed down.
Glyceryl trierucate is a 22-carbon fatty acid found in rapeseed oil. The mixture of these two fatty acids is named "Lorenzo's oil"
Proteolytic enzyme of the stomach, derived from the zymogen pepsinogen.
Pepsinogen molecule is secreted into the stomach AND undergoes a conformational change that causes it to digest itself. This is called auto-activation.
Going from a pH of about 7-8 TO 1-2 in the lumen of the stomach. This changes the charges of all the glutamate and aspartate residues and causes the protein to undergo a major conformational change, creating the active site.
After the conformational change, the N-terminal region masks the active site. Then the active is cleaved off the N-terminus exposing the active site and creating the pepsin molecule.
Once one molecule of pepsin is activated, it can cleave the N-terminus of other molecules of pepsinogen, thereby creating more pepsin molecules. This is called auto-catalysis.
In auto-activation, a given molecule of a protein acts on itself. In auto-catalysis, one molecule of a protein acts on another molecule of that protein.
MECHANISMS OF PANCREATIC DIGESTION ENZYMES
In serine proteases (such as trypsin, chymotrypsin, elastase, and some blood coagulation and complement factors), cleavage is generally between a hydrophilic area near the N-terminus and an adjoining hydrophobic area.
The hydrophilic area acts like a "buoy" pulling the hydrophobic area toward the surface of the protein molecule.
Following cleavage, the hydrophobic area, now free of the hydrophilic "buoy", sinks inside the molecule. The newly exposed N-terminal amino group makes a salt link with the carboxyl group of an aspartate or glutamate residue in the active site.
The movement of this aspartate or glutamate residue to form the salt link exposes and creates the active site. The hydrophilic portion that is cut off during zymogen activation is referred to as the activation peptide.
In certain cases, the activation peptide has no function; in others (such as complement) it acts as a messenger.
In pepsin, the active site is created by a conformational change and then unmasked by cleavage. In the second mechanism cleavage occurs first and causes a conformational change that creates the active site
CLASSICAL PATHWAY COMPONENTS
- C1 (C1q, C1r, C1s)
IgG BINDS TO ANTIGEN AND CREATES A CONFORMATIONAL CHANGE IN ITS Fc REGION WHICH INCREASES AFFINITY FOR C1q
C1q IS PART OF C1 COMPLEX (1 MOL C1q, 2 MOL C1r, 2 MOL C1s, AND 1 MOL Ca)
C1q HAS 18 SUBUNITS AND CAN BIND 6 MOLS OF IgG
STEPS OF CLASSICAL PATHWAY (11)
1) PATHOGENIC CELL ENTERS
2) IgG BINDS TO SURFACE AT LOCATION ARBITRARILY CALLED SITE 1
3) C1 COMPLEX BINDS TO IgG, WITH C1q BINDING TO THE CH
2 DOMAIN OF IgG
4) C1q UNDERGOES CONFORMATIONAL CHANGE CAUSING IT TO CLEAVE AND ACTIVATE ITSELF. C1r IS ACTIVATED AND CLEAVES OTHER C1r, WHICH CLEAVES AND ACTIVATES C1s
5) C1s IS A PROTEOLITIC ENZYME AND CLEAVES C4 AND C2. MANY C4 AND C2 MOLs CAN BE ACTIVATED BY C1s, ILLUSTRATING AMPLIFICATION
6) C4b AND C4a FORM C4,2 COMLEX THAT BINDS TO NEW SITE 2
7) C4,2 IS A PROTEASE SPECIFIC FOR C3. IT CLEAVES INTO FRAGMENTS C3a AND C3b
- 8a) C3b BINDS TO PATHOGENIC CELL DISTINCT FROM SITE 2
- 8b) 1 C3b BINDS TO C4,2 COMPLEX TRANSFORMING IT INTO C4,2,3 COMPLEX, WHICH IS NOW SPECIFIC FOR C5
9) C4,2,3 COMPLEX CLEAVES C5 INTO C5a AND C5b
10) C5b, C6, C7, C8 AND 6 MOLECULES OF C9 FORM MAC COMPLEX AT SITE 2
11) MAC OPENS CHANNELS IN SURFACE AND LYSES CELL
SPECIAL ABOUT C3a, C4a, AND C5a
ANAPHYLATOXINS WHICH INCREASE VASCULAR PERMEABILITY, CONTRACTION OF SMOOTH MUSCLE, AND RELEASE OF HISTAMINES FROM MAST CELLS.
C3a AND 5a PARTICULARLY POTENT
C5a IS CHEMOTACTIC FACTOR
INVOLVEMENT OF THIOESTER IN CLASSICAL PATHWAY
PRESENT AS POST-TRANSLATIONAL MODIFICATION (LINKING CYSTEIN AND GLUTAMINE) IN CERTAIN PROTEINS (C3 & C4)
FORMATION IS SPONTANEOUS (DOES NOT REQUIRE ENZYME)
WHEN THIOESTER IS CLEAVED, ENDS BECOME HIGHLY REACTIVE TO OH-R. C3b AND C4b USE THIS TO BIND TO BACTERIA
C-REACTIVE PROTEIN (CRP)
APPEARS DURING SEVERE INFLAMMATIONS
BINDS TO CERTAIN LIPIDS AND BACTERIAL POLYSACCHARIDES
ONCE BOUND, THEN BINDS C1q CAUSING ACTIVATION OF C1 AND REST OF COMPLEMENT COMPONENTS.
CRP CAN SUBSTITUTE FOR IgG
USED AS MARKER FOR CORONARY ARTERY DISEASE
ALTERNATE PATHWAY COMPONENTS
- B, D, H, I, & P
ALTERNATIVE PATHWAY SUMMARY
DEFENSE AGAINST PATHS FOR WHICH THE HOST MAY NOT HAVE Ab. DOES NOT NEED Ab TO BEGIN
IgM CAN ON OCCASION INITIATE THE PATHWAY
IMAGINE PATHWAY CONTINUALLY GETTING STARTED AND ITS CONTINUATION ID DEPENDENT ON PRESENCE OF PATHOGEN
ALTERNATIVE PATHWAY STEPS (12)
1) C3 REACTS WITH WATER (THIOESTER REACTION) PRODUCING C3-H2
0 BINDS WITH B & D FORMING C3 CONVERTASE. D BECOMES ACTIVE PROTEOLYTIC ENZYME
3) C3 CONVERTASE CLEAVES C3 MAKING C3a AND C3b USING D. C3b CAN EITHER BIND TO PATHOGEN, TO NON-ACTIVATING SURFACE, OR TO WATER. BINDING TO PATH CONTINUES ALT PATHWAY!!!
- 4a) IF C3b BINDS TO WATER, INACTIVATED BY H & I (H ENHANCES PROTEOLYTIC ENZ I)
- 4b) IF C3b BINDS TO NON-ACTIVATING SURFACE, INACTIVATED BY H & I
5) C3b BOUND TO PATHOGEN SETS UP SITE FOR B. D JOINS AND CLEAVES/ACTIVATES B, WHICH LAUNCHES REST OF PATHWAY. Ba FROM N-TERMINUS OF B AND IS BY-PRODUCT OF ACTIVATED COMPLEX IS CHEMOTACTIC FOR NEUTROPHILS
6) Bb BINDS TO C3b FORMING C3b,Bb COMPLEX WHICH IS PROTEOLYTIC ENZYME FOR C3
7) C3b,Bb COMPLEX CLEAVES/ACTIVATES MOLECULES OF C3
8) C3b FORMED IN 7 BINDS TO NEARBY SURFACE AND MEDIATES IMMUNE ADHERENCE, OR BINDS TO C3b,Bb COMPLEX TO FORM C3bn
,Bb COMPLEX SPECIFIC FOR CLEAVING C5
9) PROPERDIN (P) ADDS TO C3bn,Bb TO FORM C3bn,P,Bb WHICH STABILIZES THE COMPLEX
10) C3bn,P,Bb CLEAVES C5
11) C5b ACTIVATES REST OF COMPLEMENT PATHWAY AS IN CLASSICAL PATHWAY
12) PATHOGENIC CELL LYSES
REGULATION OF COMPLEMENT
- 1) RAPID DECAY
- C3 & C4 HIGHLY UNSTABLE DUE TO THIOESTER BOND
- 2) ENZYMATIC INACTIVATION OF C3a, C4a, C5a, AND Ba
- REMOVAL OF THEIR C-TERMINAL ARGININES BY SERUM CARBOXYPEPTIDASE B
- 3) INHIBITION OF COMPLEMENT BY SPECIFIC PROTEIN FACTORS
- H & I INHIBIT C3b
- 4) DECAY-ACCELERATING FACTOR (DAF)
- ERYTHROCYTES AND MANY OTHER HOST CELLS IN BLOOD CONTAIN DAF WHICH ACCELERATES DESTRUCTION OF C3b BY H & I
PEOPLE WITH PAROXYSMAL NOCTURNAL HEMOGLOBINURIA OFTEN LACK DAF. URINE TURNS RED AT NIGHT DUE TO INCREASED DESTRUCTION OF ERYTHS
INTRINSIC PATHWAY SUMMARY FOR COAGULATION
BEGINS WHEN BLOOD TOUCHES ABNORMAL SURFACE
TRIGGERED BY ELECTROSTATIC INTERACTIONS BETWEEN (-) SURFACE AND (+) LYSINE RESIDUES IN FXII
ENDS WHEN FX IS ACTIVATED
INTRINSIC PATHWAY COAGULATION STEPS (7)
1) XII BINDS TO SURFACE
2) XIIa CLEAVES/ACTIVATES PREKALLIKREIN
3) KALLIKREIN CLEAVES/ACTIVATES XIIa TO FORM XIIb
4) XIIb CLEAVES AND ACTIVATES XI
5) XIa CLEAVES/ACTIVATES IX
6) IXa COMBINES WITH VIIIa, Ca, AND A MEMBRANE
7) THIS COMPLEX CLEAVES/ACTIVATES X
EXTRINSIC PATHWAY SUMMARY OF COAGULATION
INITIATED BY TISSUE FACTOR (TF)
ENDS WHEN X IS ACTIVATED, WHICH IS LOCATED ON MEMBRANES OF ENDOTHELIAL CELLS.
WHEN MEMBRANES DAMAGED, TF CONFORMATIONALLY CHANGES AND ACTIVATES, BINDS TO VII
TF NOT AN ENZYME
STEPS OF EXTRINSIC PATHWAY COAGULATION (5)
1) TF ACTIVATED
2) TF BINDS TO VII AND PATIALLY ACTIVATES
3) VII CLEAVES/ACTIVATES X
4) Xa CLEAVES VII AND INCREASES ITS ACTIVITY
5) VIIa CLEAVES/ACTIVATES MORE X. VIIa ALSO CLEAVES/ACTIVATES IX WHICH CONNECTS INTRINSIC/EXTRINSIC PATHWAYS
STEPS OF COMMON PATHWAY COAGULATION (5)
1) Xa COMPLEXES WITH Va, Ca, AND A MEMBRANE
2) THIS COMPLEX CLEAVES/ACTIVATES PROTHROMBIN (II)
3) THROMBIN CLEAVES FIBRINOGEN (I) AND MAKES FIBRIN AND FIBRINOPEPTIDES A & B
4) FIBRIN AGGREGATES TO FROM SOFT CLOT
5) XIIIa CROSS-LINKS FIBRIN TO FORM HARD CLOT. XIIIa IS A TRANSGLUTAMINASE THAT CROSS-LINKS GLUTAMINE TO LYSINE
FACTOR V IN COAGULATION
NOT AN ENZYME
ACTS TO MAKE CLEAVAGE OF THROMBIN FASTER
CLEAVED BY Xa AND THROMBIN (CLEAVAGE BY THROMBIN EXAMPLE OF FEED-FORWARD ACTIVATION)
FACTOR VIII IN COAGULATION
SIMILAR TO V
CLEAVED BY IXa, Xa, AND THROMBIN
NOT AN ENZYME
ACCELERATES CLEAVAGE OF X
FACTOR XIII IN COAGULATION
MADE BY CLEAVAGE OF INACTIVE PRECURSER BY THROMBIN
PRODUCT NOT PROTEOLYTIC ENZYME BUT TRANSGLUTAMINASE (CROSS-LINKING ENZYME)
METHODS FOR REGULATING COAGULATION (5)
1) DILUTION OF ACTIVATED COAGULATION FACTORS
- 2) REMOVAL BY LIVER CELLS OF ACTIVATED COAGULATION FACTORS
- IF PROTECTIVE OLIGOSACCHARIDE IS LOST THROUGH ACTIVATION, COAG FACTORS ARE DESTROYED THROUGH LIVER CELLS
- 3) INACTIVATION OF ACTIVATED COAG FACTORS
- a2-MACROGLOBULIN INACTIVATES SEVERAL PROTEOLYTIC ENZYMES GENERATED IN COAGULATION. ENZYME ACTS ON a2 CAUSING CONFORMATIONAL CHANGE THAT TRAPS IT. COVALENT BOND FORMED BETWEEN a2 AND EZYME (THIOESTER IN a2). ALSO a2 LOSES OLIGOSACCHARIDE AND THEN DESTROYED BY LIVER
ANTITHROMBIN III INHIBITS THROMBIN AND ALL PROTEOLYTIC ENZYMES. ENHANCED BY HEPARIN
a1-ANTITRYPSIN, TF INHIBITOR, SERPIN, AND PROTEIN Z
- 4) DESTRUCTION OF VIIIa AND Va
- ACTIVATED PROTEIN C (APC) CLEAVED BY THROMBIN (REQUIRES THROMBOMODULIN)
- 5) DISSOLUTION OF BLOOD CLOTS
- THROMBIN --> tPA --> PLASMIN = FIBRINOLYSIS = UROKINASE <-- KALLIKREIN
ALSO, PLASMINOGEN BINDS TO FIBRIN CLOT AND tPA OR UROKINASE BINDS TO FIBRIN AND CLEAVES/ACTIVATES PLASMINOGEN. PLASMIN LYSES CLOT
LIPOPROTEIN A (LpA) COMPETES WITH WITH PLASMINOGEN FOR BINDING FIBRIN (ENHANCES CLOTTING)
ROLE OF VITAMIN K IN COAGULATION
NEEDED TO MAKE g-CARBOXYGLUTAMATE POST-TRANSLATIONALLY
g-C IS UNUSUAL AA THAT Ca BINDS ON MEMBRANES
VII, IX, X, PROTHROMBIN, AND PROTEIN C NEED Ca FOR ACTION OR ACTIVATION
VK TARGET FOR ANTICOAG THERAPY. DICUMAROL AND WARFARIN ARE COMPETITIVE INHIBITORS OF CARBOXYLATION REACTION (RESEMBLE VK)
VON WILLEBRAND FACTOR/DISEASE
LARGE IMPORTANT PROTEIN IN COAGULATION
HELPS VIII AND PLATELETS INTERACT WITH EACH OTHER
FACILITATES INTERACTION BETWEEN PLATELETS AND DAMAGED ENDOTHELIAL CELLS AT WOUND SITE
MOST COMMON BLEEDING DISORDER
TYPES OF MUTATIONS (4)
- POINT PUTATIONS
- 1) TRANSITION - SUBSTITUTION OF PURINE FOR PURINE OR PYRIMIDINE FOR PYRIMIDINE
2) TRANSVERSION - SUBSTITUTION OF PURINE FOR PYRIMIDINE OR PYRIMIDINE FOR PURINE
- READING FRAME SHIFTS
- 3) DELETION
CAUSES OF GENETIC MUTATIONS
1) DEAMINATION - A-->HX, G-->X, X-->U, CAUSES DIFFERENT BASE PAIRING PROPERTIES
- 2) COVALENT MODIFICATION
- ALKYLATION - ETHYLENE OXIDE AND BENZO MODIFY GUANINE
- 3) CROSS LINKING
- PSORALIN DERIVATIVES ACIVATED BY UV LIGHT
- MITOMYCIN C AND CISPLATIN AS CHEMOTHERAPY
- 4) RADIATION DAMAGE
- DNA FRAGMENTATION
- THYMIDINE DIMERIZATION
CONSEQUENCES OF MUTATIONS (3)
SILENT MUTATIONS - SUBSTITUTION, USUALLY IN WOBBLE ZONE RESULTING IN SAME AA
MISSENSE MUTATION - SUBSTITUTION OF DIFFERENT AA
NONSENSE MUTATION - STOP CODON
METHYL-DIRECTED MIS-MATCH REPAIR (3)
SUBSTITUTION CAUSES HEMI-METHYLATION
1) FINDING MIS-MATCH - LOOK FOR BULGES CAUSED BY MIS-MATCH
2) REMOVAL OF MIS-MATCH - METHYLATION ON PARENT GROUP DIRECTS EXPNUCLEASE
3) REPAIR - DNA POL B AND DNA LIGASE
REPAIR OF UV DAMAGE IN DNA
UV LIGHT CAUSES COVALENT LINKING OF ADJACENT THYMINE BASES FORMING DIMERS WHICH INHIBIT REPLICATION AND TRANSCRIPTION
DNA PHOTOLYASE BREAKS LINKAGE
NUCLEOTIDE EXCISION REPAIR SCANS FOR BULKY DIMERS, NEW DNA SEG SYNTHED BY DNA POL I, THEN DNA LIGASE
BASE EXCISION REPAIR (3)
REPAIRS MANY DIFFERENT MUTATIONS INCLUDING DEAMINATED BASES, OXIDIZED BASES, AND AP SITES
1) FINDING DAMAGE - GLYCOSYLASE CLEAVES BOND BETWEEN BASE AND SUGAR
2) REMOVAL - BASE REMOVED, THEN BACKBONE BY AP ENDONUCLEASE AND SUGAR REMOVED BY AP LYASE
3) REPAIR - DNA POL AND LIGASE
MUATION IN GENES OF NUCLEOTIDE EXCISION REPAIR PATHWAY
- SENSITIVITY TO UV LIGHT, SUNBURN, ULTRA-DRY SKIN, BLISTERS, MULTIPLE SKIN TUMORS
- UV CAUSES THYMINE DIMERS WHICH ARE NOT REPAIRED
- DAMAGE PERSISTS LEADING TO MUTATIONS
- AVOID UV, FREQUENT SKIN/EYE EXAMS, PROMPT REMOVAL OF TUMORS
HEREDITARY NONPOLYPOSIS COLON CARCINOMA (HNPCC)
AKA LYNCH SYNDROME
DEFICIENCY IN PROTEINS AND ENZYMES OF METHYL-DIRECTED MIS-MATCH REPAIR SYSTEM
- INCREASED RISK COLON CANCER (80%) AND OTHER CANCERS
- DEFECT IN MIS-MATCH REPAIR SYSTEM DUE TO MUTATION IN GENES (hMSH2, hMLH)
- UN-REPAIRED MUTATIONS
- UNRESTRAINED CELL GROWTH
ATAXIA-TELANGIECTASIA AND BLOOM'S SYMDROME
- LOW WBC, RBC, PLATELETS, INCREASED GENOMIC INSTABILITY AND RISK FOR LEUKEMIA/LYMPHOMAS/CANCERS/CHROMO TRANSLOCATIONS AND RECOMBINATIONS
- ATAXIA-TELAGIECTASIA - DEFECT IN ENZYMES THAT REPAIR DOUBLE STRANDED DNA BREAKS (PHOSPHODIESTER)
BLOOM'S - DEFECT IN DNA LIGASE
- AVOID INONIZING RADIATION, REGULAR CHECKUPS FOR TUMORS, ERYTHROPOIETIN, BONE MARROW TRANSPLANT
MUTATION IN BRCAI GENE
HEREDITARY AND AFFECTS PRODUCT WHICH PARTICIPATES IN DNA REPAIR
MUTATION FOUND IN THIS GENE INCLUDE ALTERED SPLICE SITE, NONSENSE AND FRAMESHIFT MUTATIONS
CAUSED BY MUTATION IN PROMOTER REGION
TRANSLOCATION BETWEEN 8 AND 14 CAUSES DEREGULATION OF C-MYC PROTEIN AND OVEREXPRESSION LEADING TO UNRESTRAINED CELL DIVISION
TERTIARY STRUCTURE MADE OF 8 ALPHA HELICES
WIDE VARIANCE IN GLOBIN SEQUENCES, BUT CONSERVED REGIONS (HYDROPHOBIC) ALLOWS FOR FOLDING INTO IDENTICAL STRUCTURE
HIS F8, ASP FG1, TYR HC2, AND HIS HC3 IMPORTANT FOR Hb BINDING TO 02
STRUCTURE OF HEME
COMPOSED OF ORGANIC AROMATIC RING STRUCTURE CALLED PROTOPORPHYRIN (Fe-PROTO WHEN BOUND TO IRON).
PORPHYRIN RING COMPOSED OF 4 PYROLE RINGS BRIDGED BY METHINE BRIDGES. ATTACHED TO PYROLE RINGS ARE 2 PROPIONATE GROUPS, 4 METHYL GROUPS, AND 2 VINYL GROUPS
- STABILIZE HEME WITH Hb:
- 1) COVALENTLY LINKED Fe VIA PROXIMAL HIS F8
2) (+) RESIDUES IN POCKET STABILIZE (-) PROPIONIC GROUPS
3) HEME TIGHTLY PACKED IN HYDROPHOBIC BINDING POCKETS THAT A) CREATE VAN DER WAALS FORCES B) PREVENTS H20 EXPOSURE AND C) PREVENTS Fe(2+) OXIDATION TO Fe(3+)
- 6 LIGANDS CAN BE BOUND TO Fe(2+):
- 1-4 PYROLE RING NITROGENS
- 5TH PROXIMAL HIS F8
- 6TH 02, CO, NO, AND H2S
Hb WITH ONLY 5 LIGANDS CALLED DEOXYHEMOGLOBIN & 02 AS 6TH CALLED OXYHEMEOGLOBIN
02 BINDS CAUSING TRANSFER OF ELECTRONS FROM Fe AND RESONANCE STRUCTURE Fe2+/O2 AND Fe3+/O2-
DISTAL HIS E7 STABILIZES
Hb WITH Fe3+ (METHEMOGLOBIN) DOES NOT BIND O2
STRUCTURE OF Hb
SIMILAR TO Mb, BUT Hb FUNCTIONS AS TETRAMER AND POSSESSES A HYDROPHOBIC PATCH (ABSENT IN Mb) TO MEDIATE A QUARTERNARY STRUCTURE.
FUNC TETRAMER COMPOSED OF PAIR OF ab DIMERS, OR DIMER OF DIMERS
- 1) FIXED INTERFACE BETWEEN a1 AND b1 & a2 AND b2
- 2) VARIABLE INTERFACE BETWEEN a1 AND b2 & a2 AND b1. LEADS TO CONFORMATIONAL CHANCE UPON 02 BINDING
Hb IS ALLOSTERIC AND BINDING OF O2 CHANGES a1b1 RELATIVE TO a2b2 (R STATE CALLED OXYHEMOGLOBIN
DURING T STATE, 2,3-BPG CAN BIND AND ACT AS NEGATIVE MODULATOR OF Hb
HIS F8, ASP FG1, TYR HC2, HIS HC3 CLOSE TOGETHER IN TERTIARY STRUCTURE AND INDUCE CONFORMATIONAL CHANCE DURING 02 BINDING
6 DIFFERENT CHAINS - b,g,d,&e ON CHROM 11 AND z,a ON 16
a,b, AND g HAVE 2 TYPES
VARIOUS COMBINATIONS OF CHAINS CREATE DIFFERENT FORMS OF Hb, BUT ONLY PRODUCTS ON SAME GENE ARE INTERCHANGEABLE
DIFFERENT EXPRESSION OF THESE CHAINS DURING DEVELOPMENT ALLOWS FOR VARYING 02 LEVELS. PREDOMINANT ADULT FORM IS HbA CONSISTING OF 2 a AND 2 b CHAINS
ASP FG1, TYR HC2, AND HIS HC3 ALL CONSERVED AMONG b ISOFORMS
- THALASEMIA CAUSED BY LACK OF EITHER a OR b CHAINS
- a-THAL LACKS a CHAIN, 4 b CHAINS CANNOT EFFICIENTLY RELEASE 02
- b-THAL LACKS b CHAIN, a CHAINS BY THEMSELVES ARE NOT SOLUABLE AND ARE NONFUNCTIONAL
SINGLE GLU6-->VAL6 MUTATION AT POSITION A3 ON SURFACE OF b-SUBUNIT
DECREASED SOLUBILITY esp DEOXY FORM
HYDROPHOBIC PATCH ON SURFACE OF T-STATE (DEOXY) b-SUBUNIT CAUSES ASSOCIATION WITH HYDROPHOBIC PATCH MADE BY PHE85 AND LEU88 ON OTHER b-SUB.
EFFECTS NOT SEEN IN R-STATE AS PHE85 AND LEU88 ARE BURIED
HYDROPHOBIC INTERACTIONS LEAD TO FIBERS WHICH CHANGE RBC SHAPE
HbS CELLS DO NOT STAY IN CIRCULATION AS LONG, CAUSING ANEMIA
OTHER Hb MUTATION METHEMOGLOBIN REFERS TO ANY MUTANT Hb THAT CAUSES OXIDATION OF Fe2+ TO Fe3+
Hb CONFORMATIONAL CHANGE
CHANGE FROM T TO R STATE INVOLVES a1b2 AND a2b1 INTERACTION
T STATE STABILIZED BY APOLAR AND IONIC INTERACTIONS LOCATED MOSTLY? ON b-SUBUNIT
HIS F8 - PROXIMAL HIS BOUND TO Fe2+ IN BOTH T/R STATES
ASP FG1 - FORMS IONIC BOND WITHIN b-SUB WITH FULLY PROTONATED HIS HC3 SIDE CHAIN
TYR HC2 - SIDE CHAIN HYDROXYL GROUP FORMS HYDROGEN BOND TO BACKBONE CARBONYL OF VAL FG5
HIS HC3 - SIDE CHAIN FORMS IONIC BOND WITHIN b-SUB WITH ASP FG1. REQUIRES FULLY PROTONATED HIS. ITS TERMINAL COO- PARTICIPATES IN IONIC BOND BETWEEN SUBUNITS
REGULATION OF Hb O2 BINDING BY pH AND CO2.
OTHER THAN COOPERATIVITY, BOHR EFFECT IS MOST IMPORTANT FACTOR IN DETERMINING THE PERCENT OF O2 BOUND IN THE LUNGS THAT IS DELIVERED TO TISSUES
pH DECREASE CAUSES O2 AFFINITY DECREASE
CO2 INCREASE CAUSES O2 AFFINITY DECREASE
Mb NOT AFFECTED BY pH
HIS HC3 - TO UNLOAD O2 (R TO T STATE), MUST BE PROTONATED (LOW pH HELPS), THEN IONIC BOND FORMED WITH ASP FG1 WITHIN b-SUB.
CO2 AFFECT Hb FUNCTION
- DIRECT ROLE (10-14% OF CO2 TRANSPORT)
- INVOLVES N-TERMINUS OF EACH OF 4 SUBUNITS.
EACH N-TER FORMS COVALENT CARBAMATE OR CARBAMINO COMPOUND WITH CO2 WHICH FAVORS O2 RELEASE IN 2 WAYS.
1) RELEASES PROTONS WITH REDUCES pH AND FAVORS T STATE AND 02 RELEASE
2) (-) CARBAMATE USES SALT BRIDGE INTERACTIONS THAT STABILIZE THE T STATE
- INDIRECT ROLE
- CO2 IN TISSUES DIFFUSES INTO RBCs AND REACTS WITH H2O FORMING CARBONIC ACID (H2CO3)
10^6 - 10^7 TIMES FASTER WITH CARBONIC ANHYDRASE
H2CO3 SPONT BREAKS DOWN TO H+ AND HCO3- (BICARB). H+ RELEASE STABILIZES T STATE
HCO3- LEAVES RBC THROUGH SPECIFIC MEM TRANS PROTEIN IN EXCHANGE FOR Cl- IN PLASMA
EFFECTS OF 2.3-BPG
ALLOSTERIC MODULATOR OF Hb, ONE CAN BIND PER Hb
SYNTHED IN RBCs FROM GLUCOSE
(-) 2,3-BPG BINDS IN (+) POCKET BETWEEN b-SUBUNITS ONLY IN T STATE
MORE T STATE Hb CAUSES MORE UNLOADING OF 02 IN TISSUES
CO POISONING EFFECTS ON Hb
AFFINITY FOR CO IS 200 TIMES GREATER THAN 02
BINDING CAUSES LEFTWARD SHIFT IN OXYHEME DISSOCIATION CURVE, IMPEDING O2 DELIVERY TO TISSUES