Chapter 10 - Carbohydrates
Terms in this set (17)
What are Carbohydrates?
Small individual particles to complex polymers
-polyhydroxyl aldehydes or ketones - which are hydrophillic thus water is associated with them in organisms
What is the difference between Aldehyde and Ketone?
Aldehyde - one C, one H gr and one R group with double bonded O group
Ketone - two R groups with double bonded O group to a central C
What are the different types of Isomers?
1. Constitutional - differ in order of attachment of atoms
2. Stereoisomers - atoms connected in the same order but differ in spatial arrangement
What are the different subgroups of stereoisomers?
1. Enantiomers - mirror images
2. Disatereoisomers - not mirror images
-this can be further subdivided to
Epimers - differ at one of several asymmetric C atoms
Anomers - isomers differ at new asymetric C atom - formed on ring closure
What are the characteristics of common Monosaccarhides?
-5C sugar moiety of nucleic acids (aldoses)
-6C - 4 main forms:
-3 aldoses (CHO)- glucose,mannose,galactose
-1 ketone (CdoublebondedO)-fructose
How are D and L isomer forms determined?
By configuration of asymeteric C atom farthest from aldehyde or ketone group
What are the possible cyclic forms?
Cyclic meaning ring strucutre - either Hemiacetal or Hemiketal
- one R group made from aldehyde plus alcohol
-usually in Puran form - 6C ring
- two R groupa made from ketone n alcohol
-usually in Furan 5C ring form
-both inert and resistant to oxidation
What is the cyclic nature of glucose?
-At pH 7.4, 37 degrees is aq environment
-99% D-glucose is hemiacetal
-one third alpha anomer - OH on bottom
-two thirds beta anomer - OH on top
-1% open chain
-forms pass through open chain form in equilibrium - open chain reacts with oxidizing agent therefore reducing sugar
What are some biological modifications for sugars?
Modifications increase biochemical versaility of carbs enabling them to serve as signal molecules or rendering them suspectible to combustion:
-Ribose vs Deoxyribose
-Glucuronic vs Gluconic acid - increases water solubility of compounds
-G6P - glycolysis
-Sorbitol - reduced suagr
What is a glycosidic bond?
occurs between anomeric C of glucose and O atom of alcohol
-carbs form ester linkages with phosphates
What is the different between Homoglycan and Heteroglycon?
Homo - single type of saccahride eg cellulose
Hetero-mixture of saccahrides eg sucrose
What is Glycosyltransterases?
-It catalyzes formation of glycosidic bonds
-General form of Glycosyltransterases reaction goes as follows:
-sugar be added comes from sugar nucleotide
-acceptor can be monosccahride, complex polysaccaride or Ser/Thr residue belonging to protein
What are the characteristics of complex carbs?
-Linkages between units is important - O-glycosidic bond
-alpha and beta positions of hydroxys and position of carbons impact bonds - often require specific enzyme
What are the different glycosidic bonds making up Glycogen and Cellulose?
-more compact, accessible store of sugar
-alpha 1-4-glycosidic bond with alpha1-6-glycosidic branches
-beta-1-4-glycosidic bonds - allows to form long straight chains
-insoluble in water and indigestible
-Glycoprotein is a covalently attached protein and carb
-sigars are attached to amide N atom in the side chain of Asp (N-linkage) or hydroxyl O atom in the side chain of Ser or Threo (O-linkage)
What are Proteoglycans?
Proteins bearing covalently linked glysosaminoglycans -glycosaminoglycans are polymers of repeating dissaccarhide units - one of the units in each repeat is a derivative of clucosamine or galactosamine
What are Lectins?
Carbs on cell surfaces recognized by proteins called lectins - in animals the interplay of lectins and their sugar targets guide cell to cell contact