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48 Cards in this Set

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What UDP-glucunorate derived from?
UDP-glucose
What UDP-glucuronate a precursor to (6 types of molecules)?
~proteoglycans & glucoprotein
UDP-xylose
~GLUCURONides
~iduRONATE
~bilirubin diGLUCURONide
Where do glucuronidation reactions take place?
Mostly in liver and intestine
What is mutarotation?
spontaneously change at anomeric sugar between the α and β configurations, possible by opening of the ring structure
What 2 molecules does sucrose starts has?
O-α-D-Glucopyranosyl
(1—> 2)-β-D-Fructofuranoside
Which enzyme cleaves sucrose?
Invertase
Why does muturotation need to occur after sucrose cleavage?
D-fructose is in the β-form, needs to change to α-conformation
Which enz initiates fruc metab in muscles if this enz is in LARGE qty?
What is 1st step?
hexokinase
fructose --> F6P (direct glycolytic intermediate)
Diff between liver vs. muscle fruct metabl?
predominance of glucokinase in liver which is gluc specific so diff enz needed vs. hexokinase in muscle which can phosph. fruct.
Fruct metabolized by which enz in liver? 1st reaction? 2nd reaction & enz?
fructokinase
1st: fru --> F1P (commited step)
F1P aldolase
2nd: F1P ------->glycealdehyde
Faith of gyceraldehyde in fructose metabolism?
->glycealdehyde-3-P (glyceyde Kase) --> glycolysis
--->glycerol(alcohol dehyoase) ->glycer3P(kinase)-->dihydroxyacertone--> glycolysis
2 faith of glycehyldehyde in fruct metabolism?
1. phopho by glyceralhdehyde
2. Hydrolysed by alcohol dehydrogenase
percent of lactose in cow's milk?
4-5%
What type of bond in lactose?
β-1,4 glycosidic bond
Since lactose is a heiacetal, what reaction can it undergo? What does this make it?
Mutorotation
Reducing sugar
Which enz and product phosphorylase galactose?
Galactokinase
G1P
Type of enzyme epimerizes UDP-glalactose to UDP-glucose?
What other products after that?
isomerase
Gal1P --> G1P --> G6P --> glycolysis(tissues) or glucose in liver
Which enzymes involved in Classic galactosemia and
non-classic galactosemia?
Classic galactosemia: galactose-1-phosphate uridyl transferase.non-classic: galactokinase.
Whic 2 types of molecule require UDP-Galactose?
Glycoproteins
Glycolipids
Where does lactose synthesis take place? Which enzyme, made of what?
only in mammary glands
ER enz: called lactase synthetase made of glalactosyltransferease + α-lactalbumin
Which hormonal signal stimulates lactose synthesis?
Describe what happens:
Prolactin following partution
lowers Km of α-lactalbumin from 1200 to 1 mM.
What other role will galactotransferase take in the absebce of α-lactalbumin?
Function in the glycoprotein pathway
What 2 substate are needed for lactose synthesis?
UDP-glalactose
GLucose
Which enz. and type of glycosydic bond link can be hydrolysed in month?
α-amylase
INTERNAL α-1,4 glycosidic bonds randomly hydrolyzed
Where does complex CHO hydrolysis continue? what does it produce?
Small intestine: mix of disaccharide, trisaccharide, and sl oligosaccharides called limit dextrins, containing (1,6) branches
Final hydrolysis of alpha(1,6)bond are done by which type of enzyme?
glycosidases
2 ways to classify glycosidases?
1. By what part of polysacch. they cut:
endoglycosidase (middle)
exo... (end)
2. if change alpha to beta (inverting) vs. not (returning)
Where do you primarely find (1)glycolipids, (2)glycoprotein, (3)proteoglycans?
1.exoplasmic cell membrane
2. blood and cell membrane 3.ECM
Where do 1.synthesis and 2.degradation of glycoconjugates occur?
1. endoplasmic reticulum and golgi.
2.lysosome
Generalized Glycosyltransferase Reaction?
Nucleotide-Sugar + HO-Acceptor --> Sugar-O-Acceptor
enz. glycotransferase
Define proteoglycans, decriscribing main componants:
GAG-GalGalXyl-O-CH2-protein
GAG:glycoaminoglycan (repeating dissach units GalNAc or GlcNAc + uronic acid (glucuronic or iduronic))
trissacharide (gal/gla/xyl)
O-glycosidic bond to S residue of core protein
Why are proteoglycans possess lg neg charge?
Advantage?
1. residues are frequently sulfated
2. highly hydrated --> take large space in ECM (good as lubricant and molecule stucture
Proteoglycans are componant of what? Name 4
ECM
joint fluid,
humor of the eye,
arterial walls
bone and cartilage
What are glycosaminoglycans (GAGs)?
long unbranched polysacc of repeating disacc(contain either of 2 modif. sugars (N-GalNAc or N-GlcNAc, and uronic acid (glucuronate or iduronate)
2 class of glycoprotein?
carbohydrate chains that are N-linked (via an Asn), O-linked (via Ser or Thr)
Name 3 GAGs
1. Heparin (lining the arteries of the lungs, liver and skin)
2. Hyaluronates (synovial fluid, vitreous humor, ECM)
3. Keratan sulfates (cornea, bone, cartilage)
Name a common O-linked glycoprotein:
Mucins
Some mucins propreties:
-Found in gastro, resp. and resp. tract secretion
-Form protective physical barrier on skin, involv. cell-cell interactions, may mask or contain antigens
-Extended stucture = high vicoelasticity
-high in O-glycan chains
Main features of O-glycolysation:
-enzymes are called: glycolyltransferase
-enz located in gogli apparatus
-occurs pOst-translationally at Ser or Threonine residues
N-linked transferred ____ translationally to protein
co-
In glycolipids what is CHO attached to?
Carbohydrates are attached to ceramide(a sphingolipid: sphingosineplus fatty acid).
A main funtion of glycolipids?
Involved in cell-cell contact/interactions
2 main classes of glycolipids and composition? And each are found where?
-CEREBROsides: single sugar group linked to ceramide, (gal or glu) high [ ] in brain
-Gangliosides–contain sialic acid residues, longer and branched vs. cerebrosides, in cell membrane
What are sulfatides:
sulfated cerebosides
galactocerebroside has which 2 main:components
Galactose + ceramide
Galactose metabolism
Fructose metabolism
glucuronic metab