Ch 8: Carbohydrates Flashcards
Carbohydrates
made up of molecules of C, H, and O
Monosaccharides
- aldehyde or ketone, 3+ carbons, polyhydroxy, alcohols
- aka “sugar”
Fisher projections
- way of representing the 3D structure in a simplified way
- horizontal = out of plane of paper
How to find # of stereoisomers of an organic compound?
- 2^n
- where n= # chiral carbon
By changing the stereochemistry of carbons…
…you can make more versions of these molecules
Naming
- by func. group
- by # C
- Combined func. group and #C
- stereochem. of last chiral C
By functional group
- aldehyde = aldose
- ketone = ketose
By # C
SI prefix = “ose”
Stereochemistry of LAST chiral C
- D = OH on right
- L = OH on left
CH2OH
must always be kept at bottom
Epimers
- different configuration around 1 carbon
- can have multiple
- the more C you have the more epimers you are going to have
*ONLY ONE chiral center w/ diff configuration
enantiomers
- all chiral centers have different configuration
- non superimposable
If you have a diff. in stereochem in more than one chiral carbon…
…it is not an epimer
Alcohols react with ?
carbonyl groups
Cyclic sugars
- 6-member ring = pyranose
- 5-member ring = furanose
(Remove “se” at the end and add pyranose/furanose)
Alcohol + Aldehyde = ?
Hemiacetal
Alcohol + Ketone = ?
Hemiketal
isomer
same formula, diff structure
anomeric carbon
carbonyl C of cyclized sugar
- bears the aldehyde OR ketone functional group
alpha: anomeric carbon
OH opposite of D/L chiral carbon CH2OH
*OH that is formed from carbonyl C
beta: anomeric carbon
Oh same side of D/L of chiral carbon CH2OH
*OH that is formed from carbonyl C
depending on how the cyclized sugar is tied up…
makes certain molecules more reactible/digestible in organisms
Fisher Projection —> Haworth Projection
- draw ring
- # clockwise w/ 1 at anomeric carbon
- place hydroxyl groups
- right = down
- left = up - Place CH2OH
- D = up
- L = down - place anomeric - OH
- Beta = same side
- Alpha = opposite side
modifications
not all carbs will have CHO
- these changes ultimately impact the way these groups will interact w/ their surroundings
Modifications: oxidation
- aldose = aldonic acid
- primary alc = uronic acid
Modifications: reduction
aldose or ketose = alditols
Modifications: replace OH groups
- H = deoxy
- NH2 = amino sugar
mutarotation
conversion b/t alpha and beta configuration of cyclic sugar
glycosidic bonds
- anomeric C condenses w/ alcohol (-C-O-C)
- reducing sugar
- nonreducing sugar
glycosidic bonds: anomeric C condenses w/ alc
- alpha-glycosidic bond
- beta-glycosidic bond
—- named as GreekLetter(C#monosacc—>C3monosacc 2)
(doesn’t matter conformation, they maintain it while forming bond)
glycosidic bonds: reducing sugar
free anomeric C (not in glycosidic bond)
glycosidic bonds: nonreducing sugar
no free anomeric C
Disaccharides
- simplest polysaccharide
- lactose & sucrose
Polysaccharide
monosaccharides linked by glycosidic bond, also called glycans
homopolysaccharide
formed from a single type of monosaccharide
heteropolysaccharide
greater than one monosaccharide
oligosaccharide
few ( >3, but < 10) monosaccharides linked together
exoglycosidases
enzymes that hydrolyze monosaccharides at the end of a polysacc. chain
endoglycosidases
enzymes that hydrolyze the middle of polysacc. chain
structural polysaccharide: cellulose
- plant cell walls
- Beta(1–>4) D-glucose
- sheets
—–unique structure, advantageous bc tightly packed = extensive H bonds + Van der Waals - water insoluble (due partly to sheets)
- rlly only give structure to organism it is in
structural polysaccharide: Chitin
- exoskeleton of invertebrates
- Beta(1–>4) N-acetyl–glucosamine
cellulose is indigestible to humans
bc we don’t have the enzyme to digest B glycosidic bond
storage polysaccharides: starch
- glycans
- reducing sugar (free anomeric C)
- reduces osmotic pressure
- digestion
starch: glycans
- alpha-amylose = straight Alpha(1–>4) glucose
- Amylopectin = Alpha(1–>4) glucose w/ Alpha (1–>6) branched
starch: digestion
- Amylase (saliva & small intestine)
—–hydrolyzes Alpha(1–>4), Alpha-glucosidase removes 1 Glu at a time, debranching enzyme hydrolyzes Beta(1–>6) linkages
storage polysaccharides: glycogen
- animals
- structure resembles amylopectin with more branching
- digestion
glycogen: digestion
glycogen phosphorylase breaks Alpha(1–>4) from nonreducing ends, glycogen debranching enzyme breaks Alpha(1–>6)
Hydrated gels
- contain collagen in a gel-like matrix (made up of glycosaminoglycans)
- extracellular space in cells
- rlly soft solid, can take shape of its container
- can be sulfated (impacts interactions…makes them unique)
Hydrated gels: glycosaminoglycans
alternating uronic and hexosamine residue, unbranched
Hydrated gels: hyaluronic acid
shock absorber
Pectins
- what is used to make jam & jelly
- in plants
- heteogeneous polysacc
pectins: heterogeneous polysacc
- Alpha(1–>4) galacturonate with rhamose
- aggregates, requires Ca+
- highly hydrated gels
- absorbs shocks
glycoproteins
- proteins covered in sugar
- proteoglycan
- enormous
- polyanionic characteristic
- highly hydrated gels
glycoproteins: proteoglycan
covalent and noncovalent aggregations of proteins and glycosaminoglycans in the extracellular matrix
Highly hydrated gels contributes?
- contributes to squishiness thru movement of water thru pores
- absorbs shocks
Peptidoglycan
- covalently linked polysaccharide & polypeptide chain
- bacterial cell walls
bacterial cell walls
Beta(1–>4) N-acetylglucosamine
gram positive bacteria
any bacteria that absorbs a chemical called gram stain
- pretty thick
gram negative bacteria
won’t absorb a chemical called gram stain
glycosylated
- proteins w/ oligosaccharides covalently attached
- N-Linked (Asn - X - Ser or Thr, where X is any amino acid except Pro and rarely Asp)
can use polysaccharides to make modifications to?
sugars
sugar code
idea that a lot of proteins are uniquely identified by the cell by the sugars that are attached to the protein surface
N-links happen while protein is?
being synthesized
O-linked Oligosaccharide
- like a glycosidic bond
- b/t sugar & Ser/Thr (Ser/Thr have a primary alc)
- synthesized in golgi
- Ser or Thr residue (no specific sequence required)
N-linked: carbs attached to proteins
- through terminal N group of Asn
- a lot of requirements
- while protein is being synthesized
O-linked: carbs attached to proteins
- can attach to OH of Ser/Thr
- after protein synthesis
- not as picky
Function of saccharides
- glycoforms
- define proteins structure
- mediate recognition events
- antigenic determinants
- have a lot more variability & info that we can convey by using saccharides to signal & decorate proteins*
Function of saccharides: glycoforms
- same protein w/ variation in sequence, location & number of covalently attached carbohydrates
- can have a diff type of carb/oligosaccharide
Function of saccharides: mediate recognition events
- to allow entry
- SUGAR CODE
Function of saccharides: Antigenic determinants
- immunochemical markers = determined by carbs on it
“why certain blood types clot & some don’t”
