Chapter 7 Carbohydrates (slide notes) Flashcards
___________ are simplest carbohydrates:
- Aldose sugars if _______ functional group
- Ketose sugars if ______ functional group
monosaccharides
aldehyde
ketone
most abundant in living cells are _____ and ______
hexose and pentose
sugars with four or more carbons exist primarily in _______
cyclic forms
ring formation occurs because aldehyde and ketone groups react reversiby with hydroxy groups in an aqueous solution to form ________ and __________
hemiacetals and hemiketals
five membered rings are called ________ and six member rings are called _________
furanoses
pyranoses
cyclic form of fructose is ________, while glucose in the pyranose form is ________
fructofuranose
glucopyranose
monosaccharides exist in many ________ forms
isomeric forms
define isomers
have the same molecular formula but different structures
define constitutional isomers
differ in the order of attachment of atoms
define stereoisomers
atoms are connected in the same order but differ in spatial arrangment
define enantiomers
nonsuperimposable mirror images
define diasteroisomers
isomers that are not mirror images
define epimers
differ at one of several asymmetric carbon atoms
define anomers
isomers that differ at a new asymmetric carbon atom formed on a ring closure
monosaccharide stereoisomers:
an increase in the number of chiral carbons increases the number of possible optical isomers. whats a formula to quantify this?
2^n where n is the number of chiral carbons. this will tell you how many possible optical isomers there will be
almost all naturally occurring monosaccharides are the ____form.
all can be considered to be dervied from _______ or non chiral ________
D form
derived from D-glyceraldehyde
or nonchiral dihydroxyacetone
formation of a cyclic hemiacetal creates another diastereoisomeric form called an ________
anomer
define mutarotation
the alpha and beta forms of monosaccharides are readily interconverted in aqueous environments
oxidation of aldoses can make what? give examples
aldonic acid uronic acid aldaric acid lactones reducing sugar
what enyzme can be used to make oxidation products of glucose
gluconolactone oxidase
what are reducing sugars?
sugars that can be reduced by weak, oxidizing agent such as benedict reagent are called this.
to be a reducing sugar what is required.
there needs to be an open chain. Ergo all aldoses are reducing sugars and frutose (ketose) is one to due to isomerization
Sugar alcohols (______) are produced by the reduction of aldehyde and ketone groups of monosaccharides. Note for recution essentionally the =O is changed changed to OH.
Note: sugar alcohols are used in commercial food processing and in pharmaceuticals. (soribtol can prevent moisture loss thus perserving food)
alditols
isomerization can yield products that show __________
epimerization
define esterification=
free OH groups of carbohydrates can be converted to esters by reactions with acids.
esterification often dramatically changes a sugars chemical and physical properties.
sulfate esters of carbohydrate molecules are found predominatly in the proteoglycan components of connetive tissue
participate in forming salt bridges between carbohydrate chains
______formation-hemiacetals and hemiketals react with alcohols to form the corresponding _______and ______
glycoside formation
acetal
ketal
when the cyclic hemiacetal or hemiketal form of the monosaccharide reacts with an alcohol, the new linkage is a _________ and the compound is a __________-
glycoside linkage
glycoside
acetals of glucose and fructose is ________ and ______-
glucoside
fructoside
define glycosylation
attachment of glycan to protiens, lipids, or other organic molecules
the result of covalent bonding of a __ or __________ with a sugar molecules (sometimes called non enzymatic _______)
the result of covalent bonding of a protein or lipid molecule with a sugar molecules (sometimes called non enzymatic glycosylation)
glucose (D-glucose)
originally called dextrose, it is found in large quanitities throughout the natural world. it is the primary fuel for living cells. it is the perferred energy source for brain cells and cells without a mitochondria
frutose
is often referred to as a fruit sugar, because of its high content in fruit. on a per gram bsis, it is twice as sweet as sucrose; therefore, it is often used as a sweetining agent in processed food. sperm use frutose as an energy source
galactose
is necessary to synthesize a variety of important biomolecules. important biomolecules include lactose, gycolipids, phospholipids, proetoglycan, and glycoprotiens
_________ is a genetic disorder resulting from a missing enzyme in galactose metabolism
galactosemia
disaccharides
two monosaccharides linked by a glycosidic bond. linkages are named by alpha or beta conformation and by which carbons are connected
oligosaccharids contain two or more _________ linked by _______ bonds
monosaccharides linked by O-glycosidic bonds
what are some common disaccharides?
sucrose, lactose, maltose
what are homoglycans (aka polysaccharides that are homo)
contain only one type of monosaccharide. starch, glycogen, cellulose, chitin, no fixed molecular weight
what are heteroglycans
contain two or more types of monosaccharides.
N and O linked oligosacchrides that are attached to prtoeins. glycosaminoglycans (GAGs)
the _______ is the storage form of glucose in animal cells
polysaccharide glycogen
Most glucose units in glycogen are lined by α-1, 4-glycosidic bonds, with branches formed by α-1, 6-glycosidic bonds every 10 glucose units.
amylose
unbranched chains of D-glucose (alpha-1,4 linkages
cellulose is a __ of glucose units linked by beta 1,4 glycocidic bond
homopolymer
___________-formed between the anomeric carbon atom and a hydroxyl group of another molecule, and the product is called an GLYCOSIDE
O-glycosidic bond
_________-formed between the anomeric carbon atom and an amine.
n-glycosidic bond
carbohydrates can also form ester linkages to _________
phosphates
glycoproteins:
the PROTIEN IS THE LARGEST COMPONENT by weight. glycoproteins play a variety of roles including as membrane proteins
porteoglycans:
the proteins is attached to a particular type of polysaccharide called a GLYCOSAMINOGLYCAN. by weight, proteoglycans are MAINLY CARBOHYDRATE. proteoglycans play structural roles or act as lubricants
mucins or mucoprotiens:
like proteoglycans, mucins are PREDOMINANTLY CARBOHyDRATE. the protein is characteristically attached to the carbohyddrate by N-acetylgalactosamine. mucins are often lubricants
carbohydrates may be linked to ______,___, or _______ residues or proteins
asparagine, serine, or threonine
what are the three main classes of glycoproteins?
glycoproteins
proteoglycans
mucins or mucoproteins
erythropoietin
is a glycoprotein secreted by the kidney into the blood that stimulates the production of red blood cells
proteoglycans are proteins attached to _______. which makes up 95% of the proteoglycan by weight
glycosaminoglycan
where glycosaminoglycans are composed of repeating units of disaccharide, one of which is a derivative of an amino sugar and one which carries a negative charge, either as a carboxylate or sulfate
cartilage is composed, in part, of the proteoglycan _____ and cartilage
aggrecan.
not the glycosaminoglycan component of aggrecan cushions joints by releasing water on impact then rebinding water
chitin, a glycosaminoglycan found in the exoskeleton of insects is __________________________________
one of hte most abundent carbohydrates in the world
in _____, the protein component is extensively glycosylated to serine and threonine residues beginning with N-acetylgalactosamine.
a region of the protein backbone rich in serines and theronines call variable number of tandem repeats, is the site of glycosylation
mucins serve as lubricants
mucins
the human ABO blood groups reflect the specificity of glycosyltransferases. all of the blood groups share the oligossaccharide foundation called O.
in A, N-acetylgalactosamine is added to O by a specific glycosyltransferase
in B, galactose is added by another transferase.
the blood type O produced no active glycosyltransferase
General slide
glycan
binding proteins bind to specific oliosaccharides on the cell surface
lectins
are a particular class of glycans binding protiens
selectins
are cell-surface carbohydrates binding proteins that mediate transient cell-cell adhesion in the blood stream and are important in many host defense mechanisms involving those cells
glycome
the total set of sugars and glycans in a cell or organism
is there a template for glycan biosynthesis?
no there is no template. it is done is a stepwise process
_________ can result upon slight variations in glycan compostion of each glycoprotien
glycoforms
