Carbohydrates in biochemistry, Slides of Biochemistry

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CARBOHYDRATES IN BIOCHEMISTRY:

FROM SUGARS TO NUCLEIC ACIDS

CHAPTERS 7 & 8 — MONOSACCHARIDES, POLYSACCHARIDES, GLYCOCONJUGATES, AND CARBOHYDRATE ROLES IN NUCLEIC ACID CHEMISTRY PEARSON FUTCH

INTRODUCTION TO

CARBOHYDRATES

• Carbs = Cn(H 2 O)n
• General formula: 2 hydrogens and 1 oxygen for every C atom
• Roles:
• Energy: store and provide
• Structure: make up cell walls and exoskeletons
• Signaling: involved in cell signaling and immune recognition

CYCLIZATION & MUTAROTATION

• MONOSACCHARIDES CYCLIZE IN AQUEOUS SOLUTION
• HEMIACETAL FORMATION BETWEEN C=O AND – OH GROUP
• CREATES A NEW CHIRAL CENTER: THE ANOMERIC CARBON
• 𝛼 - AND 𝛽 - ANOMERS DIFFER IN OH POSITION AT ANOMERIC C
• MUTAROTATION: 𝛼 ⇌ 𝛽 INTERCONVERSION IN SOLUTION

DISACCHARIDES

• FORMED VIA GLYCOSIDIC

BONDS (CONDENSATION

REACTION BETWEEN TWO

MONOSACCHARIDES)

• COMMON EXAMPLES:
  • MALTOSE = GLUCOSE +

GLUCOSE (𝛼1→4)

• LACTOSE =

GALACTOSE + GLUCOSE

• SUCROSE = GLUCOSE +

FRUCTOSE (𝛼 1 → 𝛽2)

• BOND TYPE AFFECTS DIGESTIBILITY AND ENZYME SPECIFICITY

POLYSACCHARIDES - STRUCTURAL

• CELLULOSE (PLANTS):
  • 𝛽(1→4) LINKAGES, STRAIGHT CHAINS
  • HYDROGEN BONDING BETWEEN CHAINS ADDS STRENGTH
• CHITIN (FUNGI, ARTHROPODS):
  • SIMILAR TO CELLULOSE BUT WITH N-ACETYLGLUCOSAMINE UNITS AND OFTEN COMBINED WITH PROTEINS AND CALCIUM CARBONATE FOR ADDED TOUGHNESS

OLIGOSACCHARIDES & FUNCTION

• Found on glycoproteins and glycolipids Involved in cell- cell recognition and signaling Play roles in immune response and development

GLYCOPROTEINS N-linked (Asn) vs O-linked (Ser/Thr) Affect folding, stability, and trafficking Common in hormones, enzymes, antibodies

GLYCOLIPIDS

• LIPID + CARBOHYDRATE HEADGROUP
• FOUND ON OUTER MEMBRANE SURFACE
• INVOLVED IN CELL RECOGNITION AND SIGNALING
• IMPORTANT IN BRAIN AND NERVE TISSUE

CARBOHYDRATE ANALYSIS BENEDICT’S TEST: DETECTS REDUCING SUGARS (COLOR CHANGE) HPLC & MASS SPECTROMETRY: IDENTIFY AND QUANTIFY SPECIFIC SUGARS LECTIN ARRAYS: DETECT GLYCAN- BINDING PATTERNS ON PROTEINS USED IN FOOD TESTING, DIAGNOSTICS, AND GLYCOMICS RESEARCH

SUGARS IN NUCLEIC ACIDS

• RIBOSE (RNA) VS DEOXYRIBOSE (DNA)

DNA/RNA BACKBONE

• PHOSPHODIESTER BONDS

LINK 3'-OH TO 5'-

PHOSPHATE

• CREATES SUGAR- PHOSPHATE BACKBONE
• DIRECTIONALITY: 5' → 3'
• BACKBONE IS NEGATIVELY CHARGED AND STABLE

MODIFIED SUGARS & EPIGENETICS

• 5 - METHYLCYTOSINE: COMMON IN DNA, REGULATES GENE EXPRESSION
• 2'-O-METHYLRIBOSE: FOUND IN RNA, INCREASES STABILITY
• IMPORTANT FOR EPIGENETICS, RNA PROCESSING, AND IMMUNE EVASION

CLINICAL TIE-IN: GLYCOGEN STORAGE DISORDERS

• Type I (Von Gierke):
• Deficiency in glucose-

6 - phosphatase

• Causes low blood

sugar, enlarged liver

Type V (McArdle):

• Deficiency in muscle

glycogen

phosphorylase

• Leads to muscle

cramps during exercise

CARBOHYDRATES & DISEASE: BLOOD SUGAR AND DIABETES

• CARBOHYDRATE METABOLISM DIRECTLY AFFECTS BLOOD GLUCOSE LEVELS
• INSULIN REGULATES UPTAKE OF GLUCOSE INTO CELLS
• IMPAIRED INSULIN FUNCTION → HYPERGLYCEMIA → DIABETES
• LONG-TERM EFFECTS: CARDIOVASCULAR DISEASE, NERVE DAMAGE, VISION LOSS