Chpt.10: Carbohydrate structure and function
Define homopolysaccharide. Give an example.
-same polysaccharides Examples: glycogen starch cellulose
D and L group
D= hydroxyl group on Right side L= hydroxyl group on Left side
Structure of disaccharides sucrose
" Sucrose lacks a free aldehyde or ketone group and is thus a nonreducing disaccharide while lactose and maltose are reducing disaccharides" (Shaw PG.69)
Define heteropolysaccharide. Give an example.
-made up of different polysaccharides -ex. Glycosaminoglycans
Heteropolysaccharides
-made up of different polysaccharides -ex. Glycosaminoglycans -unbranched -repeating sulfate disaccharide units, linear -ideal for a lubricating fluid in the joints, major component of synovial fluid
Define proteoglycan. Give an example.
"(AKA mucopolysaccharides) - family of glycoproteins composed of a high molecular weight protein core to which polysaccharide glycosaminoglycan chains are covalently attached -Example?
plant cell starch
- amylose: a storage polysaccharide, not easily digested, from plants with predominantly a-1,4 bonds - amylopectin: readily digested, branches every 25 residues and side chains up to 25 residues
Define glycosaminoglycan. Give an example.
-AKA "mucopolysaccharides" are long unbranched polysaccharides consisting of a repeating disaccharide unit. -ex. Chondroitin 4-sulfate, Dermatan sulfate, heparin, hyaluronate
Distinguish between the structures (and bonds) of glycogen, starch and cellulose.
-Glycogen - is a homopolymer of glucose monomers joined by alpha 1, 4-glycosidic linkages with alpha 1, 6-glycosidic linkages forming branch points every 8 - 10 residues. Starch -Starch is a polysaccharide composed of D-glucose residues connected by alpha 1, 4-glycosidic linkages.Starch occurs as a mixture of linear amylose, composed of thousands of glucose residues linked by alpha 1, 4-glycosidic bonds, and branched, amylopectin. Cellulose -Cellulose is a long unbranched structural polysaccharide. Cellulose is composed of up to 15,000 D-glucose monomers linked by beta 1,4-glycosidic bonds.. The linear structure of cellulose is stabilized by hydrogen bonds. Humans lack a beta 1, 4- glycosidase (cellulase) enzyme and are therefore unable to digest cellulose.
Glycoprotein
-Protein covalently liked to carbohydrate chain. -found in cellular secretions, they are soluble -proteins that are destined for export -communicate between cells -maintain cell structure -self-recognition by the immune system -coagulation -mucins
Define glycoprotein. Give an example.
-Proteins found covalently attached to a variable carbohydrate oligosaccharide chain -found in cellular secretions, they are soluble -proteins that are destined for export -communicate between cells ex. Erythropoietin, prothrombin, thrombin, and fibrinogen
Glycosaminoglycans are made up of two parts:
-Uronic acid, i.e glucuronate or iduronate -two modified amino sugars: N-acetylgalactosamine and N-acetylglucosamine
Lactose
-disaccharide -found in the milk of mammals -made up of galactose and glucose -hydrolyzed/broken down by lactase- which is absent in lactose intolerant
Maltose
-disaccharide -made of two D-glucose residues -bound together by alpha-1,4-glycosidic link
Structure of maltose
-disaccharide -made of two D-glucose residues -bound together by alpha-1,4-glycosidic link
Structure of lactose
-disaccharide -made up of galactose and glucose -hydrolyzed/broken down by lactase- which is absent in lactose intolerant
Sucrose
-disaccharide -table sugar -made of glucose and fructose linked by (1,2)-glycosidic bond -sucrose to glucose and fructose catalyzed by sucrase
Mucopolysaccarides
-family of glycoproteins under proteoglycans -made up of a protein where an glycosaminoglycan is added to a protein
Distinguish between glycoproteins and glycolipids
-glycoproteins are carbohydrate-protein combinations. -glycolipids are carbohydrate-lipid combinations.
Dermatan sulfate
-glycosaminoglycan -abundant in extracellular matrix of skin and blood vessels -antithrombotic function
Heparin
-glycosaminoglycan -variably sulphated -not found in connective tissue -natural anticoagulant
Glycogen
-how we store excess carbs in liver and muscle -often referred to as animal starch
Describe the structure of polysaccharides
-hundred of monosaccharides linked by glycosidic bond in a condensation reaction
polysaccharides
-hundred of monosaccharides linked by glycosidic bond in a condensation reaction
Carbohydrates exist where in nature?
-plant cellulose -energy stores-glycogen and starch -nucleiv acids -intercellular signaling -attract sperm cells to egg -antigens
Cellulose
-polysaccharide -the most abundant natural polymer in the world -stabilized by interchain and intrachain H-bonds -insoluble in water, not digested by humans
Proteoglycans
-resemble polysaccharides just with more protein -located in ECM (connective tissue) or may be transmembrane proteins -continually turned over by lysosomal enzymes e.g iduronidase -linkage of glycosaminoglycans to protein by specific trisaccharide
homopolysaccharides
-same polysaccharides Examples: glycogen starch cellulose
Describe the structure of monosaccharides.
-simplest end products may be attached to proteins-glycoproteins -at least 3 carbons -at least 2 OH
Monosaccharides
-simplest end products may be attached to proteins-glycoproteins -at least 3 carbons -at least 2 OH -Naming depends on the number of carbons: -triose: 3 carbons -tetroses: 4 carbons -pentoses: 5 carbons -hexoses: 6 carbons -heptoses: 7 carbons
Chrondroitin 4-sulfate
-the most abundant glycosaminoglycans -found in extracellular matrix of connective tissue, cartilage, tendon and bone
Describe the structure of disaccharides
-two monosaccharide's together joined by a glycosidic bond-covalent
Disaccharides
-two monosaccharide's together joined by a glycosidic bond-covalent
"Which one of the following statements about proteoglycans is correct? They"
A. are accurately classified as a subgroup of glycoproteins. B are homopolymers of carbohydrates. C contain a hydroxyproline rich core protein similar to collagen. D. predominate in the intracellular environment."
"Which of the following statements regarding the carbohydrates glycogen and cellulose is incorrect. They differ in:
A. the type of glycosidic bond(s) in the polymer B. their digestibility in humans. C. the fact that glycogen contains more branching than does cellulose. D. their monomeric components."
Review the major functions of carbohydrates.
Carbohydrates are important for : -intercellular communication -maintaining cell structure -key components of the extracellular matrix -work effectively as lubricants and shock absorbers -have been implicated in clot dissolution."
Which highly-sulfated glycosaminoglycan is widely used as an injectable coagulant?
Heparin
Glycosaminoglycans exception
Hyaluronic acid is unique since it is not sulfated and not attached to protein. -found in umbilical chord, synovial fluid, and vitreous humor of the eye.
Define the term ketose and aldose.
Ketose: sugar with ketone functional group I.E D-fructose Aldose: sugar with aldehyde functional group I.E D-glucose
Most carbohydrates exists in the form of?
Polysaccharides
glyconjugates
glycolipids/glycoproteins
Accumulation of the mucopolysaccharide heparin sulfate causing hepatosplenomegaly is characteristric of?
hurler syndrome
Simple molecules
hydrates of carbon
Mucopolysaccharidoses are a family of metabolic disorders caused by the absence of?
lysosome enzymes
Hurlers syndrome
mucopolysaccharides accumulate -iduronidase is not working -aka "lysosomal storage disease"
L- Glyceraldehyde
simplest carbohydrate -monosaccharide -OH group on the left
D-Glyceraldehyde
simplest carbohydrate -monosaccharide -OH group on the right
Aldoses
sugar with aldehyde functional group -D-glucose
Ketoses
sugar with ketone functional group D-fructose
Classification of carbohydrates
°Simple molecules °monosaccharides °disaccharides °oligosaccharides °polysaccharides