Carb

• Define carbohydrate
  • hydrated carbon
  • (CH2O)n≥3
  • basic units: monosaccharides
  • source from gluconeogenesis, photosynthesis
• Functions of carbohydrate
  • carbon source
  • energy source
  • temporary stores of glucose
  • structural and supportive elements
  • components of cell membranes and CT
  • antigenicity and anticoagulant
  • lubricate skeletal & adhesive
• Classification of carbohydrate
  • Monosaccharides
  • Oligosaccharides (Disaccharide and trisaccharide)
  • Polysaccharides
• Monosaccharide
  • families/class→aldoses (carbonyl at end) & ketoses
  • colorless
  • crystalline solids
  • free soluble in water but insoluble in nonpolar solvent
  • sweet taste
  • (CH2O)n=3
  • D = OH on the right; L = left
  • isomer aldohexose 6c=4 chiral carbon=2⁴=16 stereoisomer
  • enantiomer→isomer that are non-superimposable mirror images of each other
  • ibuprofen→mixture of isomer
  • epimer→isomer differ in configuration of OH and H on C2, 3, 4 of glucose vs galactose
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• Haworth projection (ring, hemiacetal)
  • pyran→6
  • furan→5
  • cis (beta)→OH up
  • trans (alpha)→OH down
• Cyclic Fischer projection
• Define glycoside
  • monosaccharides link together→glycoside bond/linkage
  • monosaccharide hemiacetal + 2nd molecule of alcohol→acetal
  • alkyl/aryl group + O2→B-D-glucopyranoside, a-D-ribofuranoside
• Derivatives of monosaccharide
  • N-glycoside (ATCGU)→anomeric carbon (c-O2) of cyclic hemiacetal +NH group of amine
  • toxic glycoside
    • ouabain (African shrub) inhibit Na K pump
    • amygdalin (bitter almond) yields (release) hydrogen cyanide on hydrolysis
  • reduction to alditols
    • carbonyl group reduced to OH by H2 & Ni catalyst
    • glucose to sorbitol for DM
  • oxidation to aldonic acids
  • B-D-glucopyranose to D-gluconic acid
• VC (ascorbic acid)
  • for dentine, cartilage, CT, bone
  • 45mg for adults, 60mg if pregnant, 80mg if lactating
  • L-ascorbic acid synthesized biochemically & industrially from D-glucose
  • B-D-glucopyranose to L-ascorbic acid
  • very easily oxidized to L-dehydroascorbic acid (physio active, found in most body fluids)
• Glucose assay
• Disaccharide
  • 2 monosaccharide
  • maltose
    • energy source (maltase)
    • blood sugar regulation
    • glycogen synthesis: store in liver & muscle; energy reserve for fasting/increased energy demands
    • alpha OH在下
    • beta (malt, barley, cereal)→major degradation product of starch
    • 2 glucose + a(1,4) glycosidic bond
  • lactose
  • energy source
  • calcium absorption
  • maintain gut microbiota→prebiotic promote growth of beneficial bacteria which ferment lactose, produce SCFAs (acetate, propionate, butyrate)
  • development of intestinal enzyme (lactase)
  • 5-8% human milk; 4-5% cow milk
  • galactose + glucose + B(1,4) glycosidic bond
  • D-galactopyranose + D-glucopyranose
  • lactose intolerance
    • primary deficiency of lactase production in small bowel
    • secondary to injury to intestinal mucosa
    • lactose not absorbed, converted by colonic bacteria to lactic acid, methane gas, H2
  • sucrose
    • sugar cane, beets, table sugar, saccharose
    • glucose + fructose + a(1,2) glycosidic bond
    • B-D-glucopyranose + B-D-fructofuranose
• Homopolysaccharide
  • starch
  • 15-20% a-amylose
  • D-glucose + a(1,4)
  • 80-85% amylopectin
  • 24-30 D-glucose+ a(1,4) bond + a(1,6) branch
  • glycogen
    • human starch
    • similar to amylopectin
    • location→7% liver, 1-2% muscle, RBC, kidneys, glial cells in brain, WBC, uterus, stomach
    • glucose + a(1,4) linkage with a(1,6) branch every 8-10 residues
  • cellulose
  • linear, unbranch D-glucose + B(1,4)
  • chitin
    • B(1,4) linked N-acetylglucosamine polymer
    • N-acetyl grp at C2
    • structural polysaccharide of invertebrates (exoskeleton), cell walls of fungi and algae
• Heteropolysaccharide
  • GAGs
    • most abundant
    • long unbranched contain repeating disaccharide with negative charge grp contain 2 modified sugars→N-acetyl galactosamine/N-acetylglucosamine & uronic acid (glucuronate & iduronate)
    • N-acetyl-D-galacto/glucosamine + uronic acid (glucuronate/iduronate)
    • location→EC space, vitreous humor of eye, synovial fluid of joints, CT
    • subgroups
      • hyaluronate
        • copolymer of N-glucuronic acid & N-acetyl-D-glucosamine
        • synovial fluid, inside of eye, IC matrix
        • B(1,4) linked glucuronic & B(1,3) N-acetyl-D-glucosamine
      • chondroitin sulfate
        • CT, cartilage
        • loss of chondroitin sulfate→osteoarthritis
        • D-glucuronic acid & N-acetyl-D-galactosamine
        • dietary supplement
      • heparin
        • glucuronic acid
        • iduronic acid
        • anticoagulant activate antithrombin 3 block thrombin
        • DVT, pulmonary emboli
      • keratan sulfate
        • cornea 10-fold>CT
        • cartilage, bone
        • large highly hydrated molecules
        • cushion to absorb mechanical shock
        • basic repeating disaccharide→3Gal B(1,4)GlcNAc B1
    • Mucopolysaccharidosis MPS
    • intra lysosomal accumulation
    • increase urine GAG
    • autosomal recessive
      
      • MPS 1
        • Hurler-Scheie
        • accumulated metabolites→dermatan sulfate & heparan sulfate
        • deficiency of a-L-iduronidase
        • most severe
        • hallmark→coarse facies, corneal clouding, mental retardation, hernias, dysostosis multiplex, hepatosplenomegaly
      • MPS 2 Hunter→dermatan sulfate & heparan sulfate
      • MPS 3ABCD Sanfilippo→heparan sulfate
      • MPS 4 Morquio→keratan sulfate
      • MPS 5 Maroteaux-Lamy→dermatan sulfate
      • MPS 7 Sly→dermatan sulfate & heparan sulfate & chondroitin
  • proteoglycans
    • heavily glycosylated glycoproteins
    • core protein with >1 C=C GAG chain
    • long, linear, negative charge due to sulfate & uronic acid
  • glycoproteins
    • cell recognition/adhesion
    • outer surface of human cells
    • antifreeze protein = tripeptide Ala-Ala-Thr 50x in artic, antarctic fish
    • hormones→FSH, LH, TSH, HcG, alpha fetoprotein, erythropoietin
• Coagulation
  • factor→serine protease
  • cleave proteins at specific sites
  • cofactors for cascade→Ca, phospholipid, VK