Chapter 8 Flashcards
carbohydrates or … are the most abundant biological molecules.
they follow the chemical formula …
saccharides; (C * H2O)n
the basic carbohydrates units are called …
monosaccharides
monosaccharides are … or … derivatives of straight-chain polyhydroxy … containing at least 3 C atoms
aldehyde; ketone; alcohols
if the carbonyl group of a saccharide is an aldehyde, the sugar is an ..
aldose
if the carbonyl group of a saccharide is a ketone, the sugar is a …
ketose
the smallest monosaccharides, those with three C atoms, are … those with four, five, six, seven, etc. C atoms are, respectively, …, …, …, …
trioses; tetroses; pentoses; hexoses; heptoses
… sugars are biologically much less abundant than … sugars
L; D
D-glucose and … are epimers with respect to C2
D-mannose
the most common aldoses include the six-carbon sugars .., …, and …
glucose; mannose; galactose
the pentose … is a component of the ribonucleotide residues of RNA
ribose
the triose … occurs in several metabolic pathways
glyceraldehyde
the most common ketoses are …, … and …
dihydroxyacetone; ribulose; fructose
alcohols react with the carbonyl groups of aldehydes and ketones to form … and …, respectively
hemiacetals; hemiketals
the configurations of the substituents of each C atom in these sugar rings (cyclic hemiacetals/ketals) are conveniently represented by their …, in which the heavier ring bonds project in front of the plane of the paper and the lighter ring bonds project behind it
Haworth projectiosn
a sugar with a 6 membered ring is known as a … in analogy with …, the simplest compound containing such a ring
pyranose; pyran
sugars with five membered rings are designated … in analogy with ..
furanoses; furan
when a monosaccharide cyclizes, the carbonyl carbon, called the … carbon, becomes a … with two possible configurations
anomeric; chiral
the pair of stereoisomers that differ in configuration at the anomeric carbon care called .. in the alpha form, the OH substituent of the anomeric C is on the … side of the sugar ring from the CH2OH group at the chiral center that designates the D or L configuration. the other form is known as the … anomer
anomers; opposite; beta
the anomers freely interconvert in aqueous solution, a process called …
mutarotation
only … can simultaneously have all five of its non-H substituents in equatorial positions
beta-d-glucose
a monosaccharide can readily shift its …, bc no bonds are broken in the process. the shift in … between the alpha and beta forms requires breaking and reforming bonds and occurs slowly in aqueous solutoin
conformation; configuration
oxidation of an aldose converts its aldehyde group to a … group, thereby yielding an …
carboxylic acid; aldonic acid
oxidation of the primary alcohol group of aldoses yields …
ex. d-glucuronic acids
uronic acids
aldoses and ketoses can be reduced under mild conditions to yield polyhydroxy alcohols known as …
e.g. ribitol –> combonent of flavin coenzymes; xylitol–> sweetener used in ‘sugarless’ gum
alditols
monosaccharide units in which an OH group is replaced by H are known as … sugars
the biologically most important of these is …, the sugar component of DNA’s sugar-phosphate backbone.
deoxy sugars; beta-d-2-deoxyribose
in …, one or more OH groups have been replaced by an amino group, which is often acetylated
D-glucosamine and D-galactosamine are the most common
amino sugars
the anomeric group of a sugar can condense with an alcohol form … and …
the bond connecting the anomeric carbon to the alcohol oxygen is termed a …
alpha; beta-glycosides; glycosidic bond
saccharides bearing anomeric carbons that have not formed glycosides are termed …, because the free aldehyde group that is in equilibrium with the cyclic form of the sugar reduces mild oxidizing agents. the identification of a sugar as nonreducing is evidence that it is a …
reducing sugars; glycoside
polysaccharides, which are also known as …, consist of monosaccharides linked together by glycosidic bonds
glycans kk
polysaccharides are classified as … or … if they consist of one type or more than one type of monosaccharide
homopolysaccharides; heteropolysaccharides
polysaccharides, in contrast to proteins and nucleic acids, form … as well as … polymers
branched; linear
a complete description of an oligosaccharide or polysaccharide includes the .., … forms, and … of all its component monosaccharide units. some of this info can be gathered through the use of specific … and .., enzymes that hydrolyze monosaccharide units in much the same way that exopeptidases and endopeptidases cleave amino acid residues from polypeptides
identities; anomeric forms; linkages; exoglycosidases; endoglycosidases
the most abundant disaccharide is …
sucrose
…, the primary structural component of plant cell walls, accounts for over half of the carbon in the biosphere
cellulose
cellulose has a highly … structure that gives it exceptional strength and makes it … despite its hydrophilicity
cohesive; water insoluble
in plant cell walls, the cellulose fibers are embedded in and cross linked by a matrix containing other polysaccharides and …, a plasticlike phenolic polymer
lignin
although vertebrates themselves do not possess an enzyme capable of hydrozlyzing the beta 1,4 linkages of cellulose, the digestive tracts of herbivores contain symbiotic microorganisms that secrete a series of enzymes, collectively known as …, that do so
cellulases
… is the principal structural component of the exoskeletons of invertebrates such as crustaceans etc and is also present in the cell walls of most fungi and many algae. it is a homopolymer of beta 1–>4 linked N-acetyl-D-glucosamine
chitin
… is a mixture of glycans that plants synthesize as their principal energy reserve
starch
starch is deposited in the chloroplasts of plant cells as insoluble granules composed of … and …
alpha-amylose; amylopectin
… consists mainly of alpha 1,4 linked glucose residues but is a branched molecule with alpha1,6 branch points every 24-30 glucose residues on average
amylopectin
osmotic pressure is proportional to the number of … in a given volume
solute molecules
starch is a reducing sugar, although it has only one residue, called the …, that lacks a glycosidic bond
reducing end
… randomly hydrolyzes the alpha 1,4 glycosidic bonds of starch
amylase
starch digestion is continued:
further hydrolysis by an …, which removes one glucose residue at a time, and by a … enzyme, which hydrolyzes alpha 1,6 and alpha 1,4 bonds, produces monosaccharides that are absorbed by the intestine and transported to the bloodstream
alpha-glucosidase; debranching enzyme
…: storage polysaccharide of animals, most prevalent in skeletal muscle and liver
glycogen
the primary structure of glycogen resembles amylopectin, but glycogen is more
highly branched
glycogen is degraded for metabolic use by …, which phosphorolytically cleaves glycogen’s alpha 1,4 bonds sequentially inward from its nonreducing ends
glycogen phosphorylase
glycogen’s highly branched structure, which has many … ends, permits the rapid mobilization of … in times of metabolic need
nonreducing ends; glucose
the alpha 1,6 branches of glycogen are cleaved by
glycogen debranching enzyme
…: unbranched polysaccharides that consist of alternating uronic acid and hexosamine residues
glycosaminoglycans
… is an important glycosaminoglycan component of connective tissue, synovial fluid, and the vitreous humor of the eye
hyaluronic acid
haparan sulfate plays a critical role in development and in wound healing. various … bind to heparan sulfate, and the formation of complexes of the glycosaminoglycan, the growth factor, and the growth factor receptor is required to initiate cell differentiation and proliferation
growth factors
plants do not synthesize glycosaminoglycans, but the …, which are major components of cell walls, which also function as shock absorbers. they are heterogenous polysaccharides with a core of alpha 1,4 linked galacturonate residues interspersed with the hexose …
pectins; rhamnose
…: an association of cells in a semisolid matrix
biofilm
glycoproteins tend to have variable carbohydrate composition, a phenomenon known as …
microheterogeneity
proteins and glycosaminoglycans in the extracellular matrix aggregate covalently and noncovalently to form a diverse group of macromolecules known as …
proteoglycans
the polypeptide chains of glycoproteins are synthesized under …
genetic control
glycoproteins tend to have variable carbohydrate composition, a phenomenon known as …
microheterogeneity
characterizing the structures of carbs and their variations is one goal of the field of …, which complements the studies of genomics
glycomics
proteins and glycosaminoglycans in the extracellular matrix aggregate covalently and noncovalently to form a diverse group of macromolecules known as …
proteoglycans
proteoglycans have a bottlebrush0like architecture, with “bristles” noncovalently attached to a filamentous hyaluronate “backbone.” the bristles consist of a … to which glycosaminoglycans are covalently linked. the interaction btwn the core protein and the hyaluronate is stabilized by a …
core protein; link protein
oligosaccharides glycosidically linked to the protein via the amide N of spefic Asn residues are known as
N-linked oligosaccharides
oligosaccharides that are covalently bonded to side chain O atoms of specific Ser or Thr residues are …
O-linked oligosaccharides
the extended brushlike structure of proteoglycans, together with the polyanionic character of their keratan sulfate and chondroitin sulfate components, cause these complexes to form …
highly hydrated gels
bacteria are surrounded by rigid cell walls that give them their characteristic shapes and permit them to live in … environments
hypotonic
bacterial cell walls are of considerable medical significance because they are in part responsible for bacterial
virulence
bacteria are classified as … or … according to whether or not they take up Gram stain
gram-positive; gram-negative
gram-positive bacteria have a … surrounding their plasma membrane, whereas gram-negative bacteria have a … covered by a complex …
thick cell wall; thin cell wall; outer membrane
the cell walls of bacteria consist of covalently linked polysaccharide and polypeptide chains, which form a baglike macromolecule that completely encases the cell. this framework is known as …
peptidoglycan
peptidoglycan’s polysaccharide component consists of linear chains of alternating beta 1,4 linked GlcNAc and …
N-acetylmuramic acid
…, an enzyme present in tears, mucus, and other vertebrate body sections, catalyzes the hydrolysis of the beta 1,4 glycosidic linkage between N-acetylmuramic acid and N-acetylglucosamine
lysozyme
almost all the secreted and membrane-associated proteins of eukaryotic cells are … oligosaccharides are covalently attached to proteins by either N-glycosidic or O-glycosidic bonds
glycosylated
In …, GlcNAc is invariably beta-linked to the aminde nitrogen of an Asn residue in the sequence Asn-X-Ser or Asn-X-Thr, where X is any amino acid except Pro and only rarely Asp, Glu, Leu, or Trp
N-linked oligosaccharides
N-glycosylation occurs …–that is, while the polypeptide is being synthesized
cotranslationally
proteins containing N-linked oligosaccharides typically are glycosylated and then …
processed
processing of n-linked oligosaccharides:
an oligosaccharide containing 9 mannose, 3 glucose, and 2 GlcNAc, is attached to the … of a growing polypeptide chain that is being synthesized by a ribosome associated with the ER
some of the sugars are removed during processing, which begins in the … (internal space) of the ER and continues in the Golgi apparatus. enzymatic trimming is accomplished by glucosidases and mannosidases
Asn; lumen
n-linked oligosaccharides contd:
additional monosaccharide residues, including GlcNAc, galactose, fucose, and sialic acid, are added by the action of specific … in the Golgi
glycosyltransferases
there is enormous … among the oligosaccharides of N-linked glycoproteins
diversity
the most common O-glycosidic attachment involves the disaccharide core … linked to the OH group of either Ser or Thr
beta-galactosyl-1–>3-alpha-N-acetylgalactosamine
o-linked oligosaccharides are synthesized in the … by the addition of monosaccharide units to a completed polypeptide chian.
Golgi apparatus
…: the variant species of a glycoprotein
glycoforms
since sugars are hydrophilic, the oligosaccharides tend to project away from the … bc carb chains are conformationally mobile, oligosaccharides attached to proteins can occupy time-averaged volumes of considerable size. in this way, an oligosaccharide can shield a protein’s …, possibly modifying its activity or protecting it from …
protein surface; surface; proteolysis
the attachment of an oligosaccharide may help determine how the protein
folds
the first evidence that unique combos of carbs might be involve din intracellular communication came with the discovery that all cells are coated with sugars in the form of … such as glycoproteins and glycolipids
glycoconjugates
…: proteins that bind carbs, ubiquitous in nature and frequently appear on cell surfaces
lectins
lectins are very specific: they can recognize individual … in particular linkages to other sugars in an oligosaccharide
monosaccharides
proteins known as … mediate the attachment between leukocytes and the surfaces of endothelial cells
selectins
