Biochemistry Exam 2 (Carbohydrates) – Flashcards
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What's the basis for defining a sugar?
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How it behaves in acid
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Aldose vs. Ketose
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Aldose - aldehyde; ketose - ketone
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Triose
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sugar with 3 carbons
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Tetrose
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sugar with 4 carbons
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Ultimate C
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The last C in a sugar
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Penultimate C
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next to last C and last chiral center
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In Fisher Projection formulas, what designates a D or L sugar?
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It is a D if the OH is to the right; it is an L if the OH is to the left
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Characteristics of Glucose
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ALDOSE - most often in D form
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Characteristics of Fructose
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KETOSE - most often in D form - has same sequence as glucose
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Epimer
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Only 1 chiral carbon differs, rather than all
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Write out the formation of a hemiacetal.
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DO IT.
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Write out the formation of a hemiketal.
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DO IT.
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The result of ring formation
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C1/2 (aldose/ketose) becomes chiral, anomeric
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In Haworth formulas, what designates an alpha and beta sugar?
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Alpha: OH is down, same as acetal end; Beta: OH is up, opposite of acetal end
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In Haworth formulas, what designates a D or L sugar?
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D: if the CH2OH is up; L: if the CH2OH is down
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Anomers
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2 compounds with one or more chiral center that differ at the anomeric C
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Anomerization
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The reaction that results in anomers from straight chain sugars
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Furanose
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5-membered ring
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Pyranose
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6-membered ring
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Why is an aldose a reducing sugar?
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It contains a free CHO
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Why is a ketose a reducing sugar?
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In the presence of base, the conversion from ketone carbonyl to aldehyde carbonyl occurs
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Enediol intermediate
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The thing that turns a ketone carbonyl into an aldehyde carbonyl
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Hemiacetal end is free/not free to open and close.
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Free
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Acetal end is free/not free to open and close.
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Not free
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Characteristics of D-Cellobiose
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Linkage: beta(1-4) Made up of glucose Formed from partial hydrolysis of cellulose
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Cellulase
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Found in microbes that reside in termites and the rumen of cow's stomachs, related to cellobiose
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Characteristics of D-Maltose
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Linkage: alpha(1-4) Made up of glucose Found in baby foods and malted milk
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Maltase
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Found in body, converts maltose to 2 glucoses, does not break up linkages in ISOmaltose
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Characteristics of D-Isomaltose
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Linkage: alpha(1-6) Made up of glucose
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Characteristics of D-Gentiobose
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Linkage: beta(1-6) Made up of glucose
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Characteristics of D-Trehalose
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Linkage: alpha1-1 Made up of glucose Non-reducing
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Functions of D-Trehalose
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Major constituent in circulating fluid of insects, energy storage compound
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Characteristics of D-Lactose
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Linkage: beta(1-4) Made up of galactose and glucose
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Lactase
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Hydrolyzes D-Lactose, discriminating
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Characteristics of D-Sucrose
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Linkage: Glu alpha(1-2)Fru Made up of Glucose and Fructose Non-reducing
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2 Classification Systems of Polysaccharides
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Function and Number of monosaccs
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Classes of Function of Polysaccs
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Structural and Storage
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Structural Polysaccs
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Cellulose, hemicellulose
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Storage Polysaccs
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Starch, glycogen
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Classes of Number of Polysaccs
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Homo and Hetero
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Homo Polysaccs
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Starch, glycogen, cellulose, chitin
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Heterogenous group
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name of polysacc takes in a wide number of compounds
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A polysacc name indicates..
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the linkage, not the number
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Linkage in Cellulose
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Glu beta(1-4) Glu
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MW: 50,000-500,000 300-2500 Glu
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Size of Cellulose
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Linkage in Chitin
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NAG beta(1-4) NAG
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Components of Hyaluronic Acid
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D-glucuronic acid and NAG
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Linkage in Hyaluronic Acid
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GluCOOH beta(1-3) NAG beta (1-4)
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Function of Hyaluronic Acid
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lubricant in synovial fluid, extracellular matrix, vitreous humor
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Glucosaminoglycans
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family of linear polymers consisting of repeating disaccs
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Examples of Glucosaminoglycans
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Hyaluronic acid, chonditrin sulfate, keratan sulfate
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Proteoglycans
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Glucosaminos connected to extracellular proteins
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Characteristics of Amylose
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Linear starch Linkage: Glu alpha(1-4) Helical structure!!
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MW: 10,000-50,000 60-300 Glu/molecule
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Size of Amylose
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Alpha amylases
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Attack amylose/amylopectin at random for a mixture of glucose and maltose
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Beta amylases
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Attack amylose/amylopectin in organized fashion, yields only maltose
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Characteristics of Amylopectin
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Branched starch Linkage: Glu alpha(1-4) and alpha(1-6) Frequency of branches: every 24-30 Glu
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MW: 300,000 1800 Glu 60 branching points
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Size of Amylopectin
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Dextrin
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Partially digested starch
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Limit Dextrin
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Digested starch all the way to alpha(1-6) branches
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Characteristics of Glycogen
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Animal starch Linkage: Glu alpha(1-4) and alpha (1-6) Frequency of branches: every 12-20
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MW: 250,000-several million 1500-20,000 Glu
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Size of Glycogen
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