Carbohydrates: Carbohydrate and Glycogen Metabolism Flashcards
CHO cell membrane molecules
glycolipids-
Oligosaccharides
CHO cell membrane molecules and extra cellular molecules
glycoproteins- Oligosaccharides
Short, non-repetitive complex carbs
oligosaccharides
Large repetitive carbs
polysaccharides
Large, repetitive carbohydrate usually attached to a protein core and found in extracellular and cell membrane molecules
glycosaminoglycans
Main plant based dietary carb
starch- glucose polymer
glucose polymer with a(1-4) and a(1-6) bonds
glycogen
amylopectin bonds
a(1-4) and a(1-6) bonds
Amylose bonds
a(1-4)
Milk sugar bonds
lactose- galactosyl-B(1-4)-glucose
Cellulose bond
B(1-4)
digestion of dietary carbs start in mouth by
salivary a-amylase
epithelial brush border enzymes
degrade oligosaccharides into monosaccharides
The digestion of starch continues in the intestine
Digestion by pancreatic enzyme
Digestion by enzymes of intestinal cells
pancreas secrete this in the lumen of the SI, and cleaves a(1-4) linkage
pancreatic a-amylase
Major Carb products that enter the stomach
dexterins
dextrins are
linear branched oligosaccharides
Products of pancreatic a-amylase
disaccharides: maltose, isomaltase
trisaccharides
Small oligosaccharides containing a-1,4 and a-1,6 linkages
Sucrase, lactase, isomaltase and glucomylase are produced in —- and located in —-
AKA- Complexes of enzymes- produced by intestinal epithelial cell and located in their brush border
Converts sucrose to glucose and fructose
sucrase
is an example of B-galactosidase
lactase
Latase (B-galactosidase) converts
lactose to glucose and galactose
cleaves a-1,6 linkages and releases glucose residues from branched oligosaccharides
isomaltase
Glucoamylase is an example of
a-glucosidase
cond in w/c lactose can not be digested and is oxidized by bacteria in gut
intestinal lactase deficiency
Final products generated by digestion of dietary CHOs
Glucose
Fructose
Galactose
Dietary fiber
indigestible polysaccharides are part of it
linkage associated with indigestible polysaccharides
B-1,4 bonds of cellulose
Glucose 2nd act. transport
Gluc moves into intestinal epithelial cell on a transport protein along with Na+
Sugars- monosaccharides- are passed into the blood using
facilitative transporter
Facilitative transporters for monosaccharides are located on —– side of intestinal cell
serosal side of intestinal epithelial cells
Major function of liver
maintenance of blood gluc level
Liver produces glucose by
glycogenolysis and gluconeogenesis
The largest stores for glycogen are
muscle and liver
muscle glycogen
APT generation and muscle contraction
Liver glycogen
Blood gluc maintenance during fasting and exercise
G-6-P –> G-1P –> UDP-Glucose
Used for:
a-
b-
a- glycogen
b- compounds like proteoglycans
utilize G-6-P
Major fate of G-6-P
enter glycolysis- produce pyruvate and generate NADH and ATP
G6p can enters the —— pathway and generate NADPH and ribose-5-phosphate
Pentose phosphate pathway
ribose-5-pathway and NADPH are major products of
Pentose phosphate pathway
PPp
NADPH from PPp
reactions such as biosynthesis of fatty acids
ribose-5-phosphate from PPp
used for nucleotide production
furanose
5member ring- monosacc
pyranose
6member ring- monosacc
a or B configuration depends on
the location of hydroxyl group on the anomeric carbon
Monosacc ox to
acids
monosacc red to
polyols
O-glycosidic bond joins
monosacc to for polymers
N-glycosidic bonds found in
nucleotides
monosaccharides are called aldose or ketose based on
the most oxidized functional group: aldehyde or ketone
stereoisomers
same chem formula- diff in position of OH on 1 or more chiral carbon
enantiomers
stereoisomers that are mirror images
epimers
stereoisomers- differ in OH position on ONLY one chiral C
Na-independent monosacc transporter
Release from intestinal epith cells into the circulation
GLUT-2
Na-independent monosacc transporter 1
monosacc uptake from the lumen
SGLT1
Glucose and galactose
fructose uptake from the intestinal lumen
GLUT-5
Na-independent monosacc transporter: From lumen into intestinal epithelial cell
GLUT-5
Fructose
Glucose and galactose uptake from the intestinal lumen into the intestinal epithelial cells
SGLT1- Na- dep
Glucose transporter in RBCs and BBB
GLUT-1
Gluc transporter opn the endothelial cells of the brain blood vessels
GLUT-1
Na-indep glucose transporters
GLUT1,2,3,4
Main bidirectional gluc transporter in LIVER, KIDNEY and PANCREAS
GLUT-2
Na-indep
Gluc transporter specific for muscle and adipose
GLUT-4
The only insulin regulated glucose transporter
GLUT-4
The only insulin dependent glucose transporters can be found in
muscle and adipose
GLUT-4
Na-indep
GlUT-2
Main bidirectional transporter in liver, kidney and pancreas
Carbohydrate absorption takes place in the
Small intestine
GAGs
Glycosaminoglycans
Composed of repeating disaccharide units of
1- acidic sugar
and
2- N-acetylated amino dugar
GAGs
Two acidic sugars found in GAGs
glucuronic
iduronic
All GAGs are attached to a protein core except
Hyaluronic acid
All GAGs, except hyaluronic acids are synthesized in
Golgi
GAGs charge
Negative
Exception to GAGs charge
GAGs negative- sulfated Except hyaluronic acid
hyaluronic acid synthesis takes place at
plasma membrane
The GAG property that conger resistance to tissue under compressive forces
“sponge behavior”H2O attracted to the NEGATIVE charge
A GAG wo an acidic sugar
KERATAN SULFATE
A GAG, unsulfated and unattached to a protein core
hyaluronic acid
heparin
GAG- Mast cells
heparin sulfate
GAG- Basement Membrane and Cell surfaces
keratin sulfate
GAG- Cartilage and cornea- Dosnt have an acidic sugar
dermatan sulfate
GAG-skin, blood vessel, heart valves
chondroitin sulfate
GA- cartilage, tendon, ligaments, aorta
Proteoglycan
protein + at least 1 GAG
The linkage region is attached to either ——- or —— of the core protein
OH of Ser or Made of Asn
trisaccharides linkage
Gal-Gal-Xyl
{?-?]n–Gal-Gal-Xyl- (Ser or Asn)
Two components of Glycosaminoglycan
[ N-acetylated Sugar- Uronic acid ] n
GAG repeating disaccharide
Important monosaccharides with a C = O group at C2 (ketoses)
fructose (6C)
Xylulose or ribulose (5C)
Dihydroxyacetone (3C)
the main path of metabolism of dietary fructose or galactose
glycolysis
the product of glycolysis in anaerobic tissues such as brain, muscle, GI tract, retina, skin and erythrocytes w/o mitochondria
lactate
glycolysis in aerobic tissues like heart, liver and kidney
glycolyze glucose to pyruvate, convert pyruvate to acetyl coA via PDH and effect complete oxidation to carbon dioxide and water using the TCA and ox-phos.