Ch. 10: Carbohydrates

Maltose

-2 glucose units joined by alpha-1,4-glycosidic linkage -comes from hydrolysis of large polymers of sugars like starch and glycogen and hydrolyzed by maltase

Intramolecular hemiacetal

-Hemiacetal that is formed within a molecule -For example when glucose cyclizes the C1 aldehyde reacts with the C5 hydroxy to form this

Beta

-Hydroxyl group attached to C-1 is above the plane of the ring

Diastereoisomers

-Isomers that are not mirror images of each other. -This is for monosaccharides composed of more than three carbons b/c they have more than one asymmetric carbon atoms -By convention L and D isomer is determined by configuration of the chiral carbon farthest from the aldehyde or ketone group Can be... Epimers: Differ at one of several asymmetric carbons

Variable number of tandem repeats (VNTR)

-defining feature of mucins -Region of the protein backbone that is rich in Ser and Thr that are O-glycosylated

Anomers

-diastereoisomers formed by the asymmetric carbon atom formed when a cyclic hemiacetal is formed

Insoluble fibers

-e.g. cellulose -Increase the rate at which digestion products pass through the large intestine, which can minimize exposure to toxins in the diet

Selectins

-A protein component of some lectins that bind immune-system cells to sites of injury -L E and P forms bind to carbohydrates on lymph-node vessels, endothelium, or activated blood platelets respectively -L form also is produced in the embryo when ready to attach endometrium of the mother's uterus

Pyranose

-A six-membered ring similar to pyran that describes the resulting cyclic hemiacetal formed by the intramolecular hemiacetalization of glucose

Glucosinolates

-A special class of glycosides present in plants (mostly brassicales) -Defense against herbivory b/c when hydrolyzed isothiocyanate is released which makes a sharp taste -Stored separate from its activating enzyme, but tissue damage brings them together

Chitin

-A type of glycosaminoglycan -Found in exoskeleton of insects, crustaceans, and arachnids, and after cellulose in the most abundant polysaccharide in nature

Glycosaminoglycan

-A type of polysaccharide that links to proteoglycans -Many made of repeating units of disaccharides w/ derivative of an amino sugar (either glucosamine of galactosamine) where at least one has negatively charged carboxylate or sulfate

Hemiacetal

-Aldehyde and alcohol can react to form this -Chemical basis for the cyclizing of sugars e.g. glucose is able to do this between the C1 aldehyde and the C5 hydroxyl group to form an intramolecular one

N-glycosidic bond

-Bond between anomeric carbon atom of a sugar

Equatorial

-Bonds on a chair or boat conformation of a pyranose ring that go nearly parallel with the average plane of the ring

Axial

-Bonds on a chair or boat pyranose ring that go perpendicular to the average plane of the ring -Sterically hinder each other (e.g. 1,3-diaxial interactions)

Oligosaccharides

-Built by linkage of two or more monosaccharides by O-glycosidic bonds -These glycosidic linkages happen at specific points on the sugars, e.g. two D-glucose residues at C-1 of one and C-4 of the other, making an alpha-1,4-glycosidic bond

Haworth projections

-Carbon atoms in the ring aren't written out, and the plane of the ring is approximately perpendicular to the paper with the heavy line projecting toward the reader

Carbohydrates

-Carbon based molecules rich in hydroxyl groups (empirical formula for many is (CH2O)n) -Can be simple (monosaccharides) or complex (polymers of covalently linked monosaccharides)

Lectins

-Class of glycan-binding proteins -Facilitate cell-cell contact, usually has 2 or more carbohydrate binding sites -So [term] on one cell interact w/ array of carbohydrates on other cell, link w/ weak noncovalent interactions that ensure specificity w/o permanence

Mucopolysaccharidosis

-Collection of diseases like Hurler disease that result from the inability to break down glycosaminoglycans. -Precise symptoms vary, but all result in skeletal deformities w/ reduced life expectancy

O antigen

-Common base among all blood types -A and B differ in the addition of one extra monosaccharide, either A (N-acetylgalactosamine) or B (Galactose) through an alpha-1,3 linkage to a galactose on the [term] -Differentiate b/c a glycosyltransferase attaches the monosaccharide, in type A it attaches N-acetylgalactosamine, in B it attaches Galactose, and in O it doesn't work. A and B enzymes are dif. in 4 a.a.

Fructose

-Commonly used as a sweetener that is converted into glucose derivatives inside the cell

Alpha

-Designates that the hydroxyl group attached to C-1 is below the plane of the ring

Epimers

-Diastereoisomers that differ at one of several asymmetric carbons -In example D-glucose and D-galactose differ in conformation at C4

Lactose

-Disaccharide of milk -Made of galactose joined to glucose by beta-1,4-glycosidic linkage -Broken into monomers by lactase in humans and beta-galactosidase in bacteria

glycosyltransferases

-Enzymes responsible for synthesizing oligosaccharides, catalyze formation of glycosidic bonds (lots of dif. types, 1-2% of total gene products in all organisms) -General form is that an activated sugar nucleotide like UDP-glocose comes in to be attached, where it is then attached -This attachment of a nucleotide to enhance energy is common in biosynthesis

Glucose

-Essential energy source for almost all forms of life -A type of reducing agent b/c alpha and beta isomers are in equilibrium that passes through open-chain aldehyde form, so has properties of free aldehydes -b/c of these free aldehyde properties can react w/ cupric ion (Cu2+) to make it cuprous ion (Cu+) as it is oxidized to gluconic acid

Congenital disorders of glycosylation

-Family of inherited human diseases that are due to improper modification of proteins by carbohydrates and derivatives

Glycoprotein

-Formed by a carbohydrate covalently bound to a protein -About 50% of the proteome is this 3 classes: glycoproteins: protein constituent largest by weight, wide variety of roles Proteoglycans: Protein component is conjugated to a glycosaminoglycan, much more carbohydrate by mass than protein, structural or lubricant Mucins/mucoproteins: Mostly carbohydrate, key component of mucus, serve as lubricants, N-acetylgalactosamine usually carbohydrate, which is an amino sugar

Furanose

-Formed by the cyclization when a ketohexose forms a intramolecular hemiketal between the C2 ketose and the C5 hydroxyl to make a 5 membered ring -Resembles furan

Hemiketal

-Formed when ketoses cyclize -The C-2 keto group in the open chain of a ketohexose (e.g. fructose) can make an intramolecular [term] by reacting with the C-6 hydroxyl for a 6 membered or C-5 for a five membered ring

O-glycosidic bond

-Join sugars, it is the bond between the anomeric carbon atom of a sugar and the oxygen atom of an alcohol -Resulting product is a glycoside -Prominent when carbohydrates are linked together to make long polymers and when they are attached to proteins

I-Cell disease (AKA mucolipidosis II)

-Lysosomal storage disease -Lysosomes will have large inclusions of undigested glycosaminoglycans and glycolipids b/c the enzyme for them is missing -The protein is made, but it gets excreted b/c they are not glycosylated they are simply excreted from the cell -Patients suffer from a lack of N-acetylgalactosamine phosphotransferase -Symptoms include psychomotor retardation and skeletal deformities

Cellulose

-Major polysaccharide of glucose makes the cell wall, one of the most abundant organic compounds in the biosphere -Unbranched polymer of glucose joined by beta-1,4 linkages, this allows it to make very long, straight chains. -These can make fibrils using parallel chains that interact via H-bonding to make a rigid supportive structure (alpha-1,4 linkages would've made a hollow helix instead of the straight chain)

Advanced glycation end products

-Modifications e.g. glycosylated hemoglobin that result from reducing sugars reacting w/ amino groups -Have been implicated in aging, arteriosclerosis, and diabetes, among other pathological conditions

Ketose

-Monosaccharides that contain a keto group (a ketone) -e.g. dihydroxyacetone

Aldose

-Monosaccharides that have an aldehyde group -e.g. glyceraldehyde

Trioses

-Monosaccharides with 3 carbons -e.g. dihydroxyacetone and glyceraldehyde -Similar other monosaccharides are named (e.g. tetroses, pentoses, hexoses, or heptoses)

homopolymer

-Polysaccharide in which all subunits are the same -Most common is glycogen, the storage form of glucose, which is common in muscle and liver -In glycogen most units are joined by alpha-1,4-glycosidic bonds, w/ branches from alpha-1,6-glycosidic bonds about every 10 units -Another example is starch

Glycoside

-Product of an O-glycosidic bond

Reducing sugars

-React with cupric ion -often nonspecifically react w/ amino groups on proteins not in a peptide bond -Integral to advanced glycation end products (AGEs)

Furan

-Resembles furanose, the five membered ring formed by some ketohexoses

Stereoisomers

-Same molecular formula and connectivity but different spatial arrangement e.g. L and D glyceraldehyde

erythropoietin (EPO)

-Secreted by the kidneys and stimulates the production of RBC by bone marrow -A glycoprotein w/ 165 a.a. and N-glycosylated at 3 Asn residues and O-glycosylated on a Ser residue (40% carbohydrate by weight) -The carbohydrate stabilizes it, increasing protein activity

pectin

-Soluble fiber that slows the movement of food through the digestive tract allowing improved digestion and absorption of nutrients

Fehling's solution

-Solution of cupric ion -give a simple test for presence of sugars like glucose that have free aldehyde properties -Sugars that react w/ Cu2+ considered reducing sugars, those that don't are nonreducing sugars

Glycan-binding proteins

-Special class of proteins that recognize complex polysaccharides that bind carbohydrate structures on neighbouring cell surfaces -Present in all living organisms -particular class lectins, partners are often carbohydrate moiety of glycoproteins

Enantiomers

-Stereoisomers that are mirror images of each other e.g. L and D glyceraldehyde

O-linkage

-Sugar attached to the hydroxyl oxygen of serine or threonine -Attachment process is glycosylation

Amino sugar

-Sugar that has an amino group that replaces a hydroxy group e.g. N-acetylgalactosamine

Sucrose

-Table sugar, a disaccharide -Formed by glucose and fructose subunit, where anomeric carbon of glucose and fructose are joined, it is alpha for glucose and beta for fructose -Cleaved into monomers by sucrase

Anomeric carbon atom

-The C that the alpha and beta designations in cyclic anomers refer to -In glucose it is the C1 atom -In fructose it is the C2

Constitutional isomers

-They have identical molecular formulas but differ in atomic connectivity e.g. dihydroxyacetone and glyceraldehyde

Disaccharides

-Two sugars joined by an O-glycosidic bond -3 common ones, sucrose (table sugar), lactose (milk), and maltose

Monosaccharides

-Used as fuel molecules or as fundamental constituents of living systems (e.g. ribose/deoxyribose in DNA) -Aldehydes or ketones w/ two or more hydroxyl groups -Smallest possible have 3 Carbons, and are dihydroxyacetone and D and L glyceraldehyde

ester linkages

-Used to join carbohydrates to phosphates, phosphorylation is needed to destabilize glucose in glycolysis

hemagglutinin

-Viral protein that binds to sialic acid linked to galactose -After binding virus engulfed by cell and begins to replicate

Aggrecan

-a proteoglycan that is a key component of cartilage -Serves as a shock absorber -protein part is 2397 aa, these are then linked together by hyaluronate (a glycosaminoglycan) and the protein itself is covered in chondroitin sulfate and keratan sulfate which bind water -able to serve as a shock absorber b/c as the tissue is squeezed the water is forced out, then it springs back when released by the water coming back in

Mucins

-protein component is high glycosylated to serine or threonine residues by N-acetylgalactosamine -Can form large polymeric structures common in mucous secretions -Synthesized by special cells in a variety of tracts, lots in saliva where they function as lubricants -Adhere to epithelial cells and give protective barrier, hydrate underlying cells -Overexpressed in bronchitis and cystic fibrosis, and also characteristic of adenocarcinomas (cancers of glandular cells of epithelial origin)

Proteoglycans

-proteins attached to glycosaminoglycans, which can be up to 95% of the total mass, so resembles carbohydrate more than protein -Function as lubricants and structural components of connective tissue, also bind factors that regulate cell proliferation -Properties mostly depend on the sugar

N-linkage

-sugar attached to the amide nitrogen atom in asparagine -attachment process is glycosylation -All sugars have a pentasaccharide core w/ 3 mannoses, and 2 N-acetylglucosamines, with addition sugars attached to this core for variety and function

Osteoarthritis

Most common type of arthritis, can result from degradation of aggrecan and collagen due to inflammation

Pyran

Six-membered ring that pyranose (cyclized glucose) resembles

Starch

Two forms: Amylose: Unbranched type, made of glucose in alpha-1,4 linkages Amylopectin: Branched form, has about 1 alpha-1,6 linkage per 30 alpha-1,4 linkages

Glycosidic bond

Two types: O-glycosidic bond: bond between anomeric carbon atom of a sugar and the oxygen atom of an alcohol N-Glycosidic bond: Bond between anomeric carbon atom of a sugar and the nitrogen atom of an amine.