Metabolism of saccharides
- exercise -
Vladimíra Kvasnicová
Glucose enter the cells by
a) free diffusion
b) facilitated diffusion
c) active transport
d) secondary active transport
Glucose enter the cells by
a) free diffusion
b) facilitated diffusion
c) active transport
d) secondary active transport
Insulin-dependent transport of glc into
the cell is found in the
a) liver
b) erytrocyte
c) adipose tissue
d) muscle
Insulin-dependent transport of glc into
the cell is found in the
a) liver
b) erytrocyte
c) adipose tissue
d) muscle
Glucose transport into cells: facilitated diffusion
(protein transporter GLUT – various types)
ERYTROCYTES
NERVOUS TISSUE
- insulin-independent transport
The figure is found at http://www.kumc.edu/research/medicine/biochemistry/bioc800/car02fra.htm (Jan 2007)
HEPATOCYTES
- insulin-independent transport
The figure is found at http://www.kumc.edu/research/medicine/biochemistry/bioc800/car02fra.htm (Jan 2007)
FATTY TISSUE
MUSCLES
- insulin-DEPENDENT transport
insulin increases number of glc transporters
The figure is found at http://www.kumc.edu/research/medicine/biochemistry/bioc800/car02fra.htm (Jan 2007)
Secondary-active transport of GLC: symport with Na+
- small intestine, kidneys
The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed.
Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2
Glucose from a diet can be used
a) as an energy source for cells
b) for glycogen synthesis
c) for formation of fat (= energy store)
d) as a main substrate for production of
NADPH
Glucose from a diet can be used
a) as an energy source for cells
b) for glycogen synthesis
c) for formation of fat (= energy store)
d) as a main substrate for production of
NADPH
Glc-6-P
!!!
+ NADPH
= hepatocyte
The figure is found at http://www.kumc.edu/research/medicine/biochemistry/bioc800/car02fra.htm (Jan 2007)
Glycolysis
(= oxidative cleavage of glucose)
a) is located in a mitochondrion
b) can proceed under anaerobic conditions as well
c) produces 2 moles of pyruvate / 1 mole of Glc
d) generates 2 moles of ATP as a net energy
acquisition
Glycolysis
(= oxidative cleavage of glucose)
a) is located in a mitochondrion
b) can proceed under anaerobic conditions as well
c) produces 2 moles of pyruvate / 1 mole of Glc
d) generates 2 moles of ATP as a net energy
acquisition
Products of aerobic glycolysis
2
Products of anaerobic glycolysis
2
NADH
was consumed in
conversion of
pyruvate to lactate
The figure is found at http://www.kumc.edu/research/medicine/biochemistry/bioc800/car02fra.htm (Jan 2007)
Enzyme hexokinase
a) catalyzes esterification of glucose
b) has higher affinity to glucose than
glucokinase
c) phosphorylates fructose as well
d) is found in a cytoplasm of many cells
Enzyme hexokinase
a) catalyzes esterification of glucose
b) has higher affinity to glucose than
glucokinase
c) phosphorylates fructose as well
d) is found in a cytoplasm of many cells
IRREVERSIBLE REACTION
The figure is found at http://www.kumc.edu/research/medicine/biochemistry/bioc800/car02fra.htm (Jan 2007)
Km
Km
The glucokinase has higher value of Kmthan hexokinase
 glucokinase has lower affinity to glucose
(it needs more glucose to reach the reaction velocity of Vmax/2)
The figure is found at http://www.kumc.edu/research/medicine/biochemistry/bioc800/car02fra.htm (Jan 2007)
Enzyme 6-phosphofructokinase-1 (PFK-1)
a) is a main regulatory enzyme of glycolysis
b) converts fructose-1,6-bisphosphate to
fructose-6-phosphate
c) is activated by citrate and  ATP/ADP
d) is regulated by insulin
Enzyme 6-phosphofructokinase-1 (PFK-1)
a) is a main regulatory enzyme of glycolysis
b) converts fructose-1,6-bisphosphate to
fructose-6-phosphate
c) is activated by citrate and  ATP/ADP
d) is regulated by insulin
IRREVERSIBLE REACTION
The figure is found at http://www.kumc.edu/research/medicine/biochemistry/bioc800/car02fra.htm (Jan 2007)
NADH+H+ forming in glycolysis
a) is a coenzyme of oxidoreductases
b) can be reoxidized back to NAD+ in a
conversion of pyruvate to lactate
c) can be used in a reduction of malate to
oxaloacetate
d) is a source of reducing equivalents entering
a respiratory chain, but only under aerobic
conditions
NADH+H+ forming in glycolysis
a) is a coenzyme of oxidoreductases
b) can be reoxidized back to NAD+ in a
conversion of pyruvate to lactate
c) can be used in a reduction of malate to
oxaloacetate
d) is a source of reducing equivalents entering
a respiratory chain, but only under aerobic
conditions
The figure is found at http://www.kumc.edu/research/medicine/biochemistry/bioc800/car02fra.htm (Jan 2007)
The figure is found at http://www.kumc.edu/research/medicine/biochemistry/bioc800/car02fra.htm (Jan 2007)
Transport of reducing equivalents to mitochondria
The figure was adopted from
Devlin, T. M. (editor):
Textbook of Biochemistry
with Clinical Correlations,
4th ed. Wiley-Liss, Inc.,
New York, 1997.
ISBN 0-471-15451-2
MALATE-ASPARTATE SHUTTLE
GLYCEROL PHOSPHATE SHUTTLE
The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed.
Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2
2,3-bisphosphoglycerate (2,3-BPG)
a) belongs among energy rich compounds
b) is formed from glyceraldehyde-3-phosphate
by phosphorylation using inorganic phosphate
c) can be transformed to 3-phosphoglycerate,
ATP is simultaneously formed from ADP
d) is formed only in the liver as a shunt of
glycolysis
2,3-bisphosphoglycerate (2,3-BPG)
a) belongs among energy rich compounds
b) is formed from glyceraldehyde-3-phosphate
by phosphorylation using inorganic phosphate
c) can be transformed to 3-phosphoglycerate,
ATP is simultaneously formed from ADP
d) is formed only in the liver as a shunt of
glycolysis
2,3-BPG shunt
IN ERYTROCYTES:
2,3-BPG  affinity of Hb to O2
The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed.
Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2
ATP is formed in the reactions of glycolysis
a) phosphoenolpyruvate (PEPA) → pyruvate
b) glucose → glucose-6-phosphate
c) fructose-1,6-bisphosphate
→ fructose-6-phosphate
d) glyceraldehyde-3-phosphate
→ 1,3-bisphosphoglycerate
ATP is formed in the reactions of glycolysis
a) phosphoenolpyruvate (PEPA) → pyruvate
b) glucose → glucose-6-phosphate
c) fructose-1,6-bisphosphate
→ fructose-6-phosphate
ATP is consumed
= not energy-rich comp.
d) glyceraldehyde-3-phosphate
→ 1,3-bisphosphoglycerate
IRREVERSIBLE REACTION
= substrate level phosphorylation
(ATP formation using energy released from cleavage of
an energy rich compound = macroergic compound)
The figure is found at http://www.kumc.edu/research/medicine/biochemistry/bioc800/car02fra.htm (Jan 2007)
Pi +
= substrate level phosphorylation
The figure is found at http://www.kumc.edu/research/medicine/biochemistry/bioc800/car02fra.htm (Jan 2007)
Pyruvate can be transformed by
a) carboxylation to acetyl-CoA
b) reduction to lactate
c) oxidative decarboxylation to oxaloacetate
d) transamination to aspatate
Pyruvate can be transformed by
a) carboxylation to acetyl-CoA
b) reduction to lactate
c) oxidative decarboxylation to oxaloacetate
d) transamination to aspatate
= transamination
= carboxylation
= reduction
= oxidative decarboxylation
The figure is found at http://www.kumc.edu/research/medicine/biochemistry/bioc800/car02fra.htm (Jan 2007)
Choose correct statements about regulation
of glycolysis
a) it is activated by insulin
b) it is activated by glucagon
c) regulatory enzymes of glycolysis are
kinases
d)  pH inhibits glycolysis
Choose correct statements about regulation
of glycolysis
a) it is activated by insulin
b) it is activated by glucagon
c) regulatory enzymes of glycolysis are
kinases
d)  pH inhibits glycolysis
Regulation of glycolysis
regulatory enzyme
activation
inhibition
 glucose-6-phosphate
hexokinase
glucokinase
 insulin (induction)
 fructose-1-phosphate
(liver)
6-phosphofructo1-kinase
(PFK-1)
  ATP / AMP
 fructose-6-phosphate
  ATP / AMP
 fructose-2,6-bisphosphate  citrate
( if  insulin / glucagon)
 acidic pH
 insulin (induction)
main regulatory
enzyme
(key enzyme)
pyruvate kinase
 insulin (induction)
 glukagon (repression,
 fructose-1,6-bisphosphate inhibition by phosphorylation)
  ATP / AMP
(feed foreward regulation)
 acetyl-CoA
Enzymes of gluconeogenesis
(= synthesis of glucose „de novo“)
a) are found in a cytoplasm only
b) are active mainly in a brain and erytrocytes
c) are completely the same as enzymes of
glycolysis (catalyze oposite reactions of
glycolysis)
d) are not found in the liver
Enzymes of gluconeogenesis
(= synthesis of glucose „de novo“)
a) are found in a cytoplasm only
b) are active mainly in a brain and erytrocytes
c) are completely the same as enzymes of
glycolysis (they catalyze oposite reactions of
glycolysis)
d) are not found in the liver
gluconeogenesis proceeds only in the liver and the kidneys
in mitochondria only
The figure is found at http://www.kumc.edu/research/medicine/biochemistry/bioc800/car02fra.htm (lJan 2007)
Gluconeogenesis
The figure is found at http://www.kumc.edu/research/medicine/biochemistry/bioc800/car02fra.htm (Jan 2007)
Choose substrates of gluconeogenesis
a) acetyl-CoA
b) pyruvate
c) glycerol
d) lactate
Choose substrates of gluconeogenesis
a) acetyl-CoA
b) pyruvate
c) glycerol
d) lactate
it can not be converted to pyruvate
Cori cycle
and muscle
The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed.
Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2
Glucose-alanine cycle
The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed.
Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2
= tuk
The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed.
Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2
Choose enzymes of gluconeogenesis
a) pyruvate kinase
b) PEP carboxykinase
c) pyruvate carboxylase
d) pyruvate dehydrogenase
Choose enzymes of gluconeogenesis
a) pyruvate kinase
b) PEP carboxykinase
c) pyruvate carboxylase
d) pyruvate dehydrogenase
Pyruvate DeHydrogenase complex is found in mitochondria
(multienzyme complex, PDH)
the reaction is IRREVERSIBLE
The figure is found at http://faculty.uca.edu/~johnc/pdhrxns.gif (Jan 2006)
The reactions participate in gluconeogenesis
a) pyruvate + CO2 → oxaloacetate
b) pyruvate + ATP → phosphoenolypyruvate
c) fructose-1,6-bisphosphate → fructose-6phosphate + ATP
d) glucose-6-phosphate → glucose + ATP
The reactions participate in gluconeogenesis
a) pyruvate + CO2 → oxaloacetate
b) pyruvate + ATP → phosphoenolypyruvate
c) fructose-1,6-bisphosphate → fructose-6phosphate + ATP
d) glucose-6-phosphate → glucose + ATP
Gluconeogenesis is
a) activated by insulin
b) inhibited by citrate
c) activated by AMP
d) inhibited by glucagon
Gluconeogenesis is
a) activated by insulin
b) inhibited by citrate
c) activated by AMP
d) inhibited by glucagon
the opposite answers are correct
Regulation of gluconeogenesis
regulatory enzyme
activation
inhibition
pyruvate carboxylase
 acetyl-Co A
 cortisol, glucagon
(induction)
 insulin (repression)
phosphoenolpyruvate
carboxykinase
 cortisol, glucagon
(induction)
 insulin (repression)
fructose-1,6bisphosphatase
 cortisol, glucagon
(induction)
  AMP / ATP
 fructose-2,6bisphosphate ( if 
insulin / glucagon)
 insulin (repression)
glucose-6phosphatase
 cortisol, glucagon
(induction)
 insulin (repression)
Metabolism of glycogen
a) is regulated by glycogen synthase and
glycogen phosphorylase
b) is located in a cytoplasm
c) is regulated by insulin
d) proceeds on reducing ends of glycogen
molecule
Metabolism of glycogen
a) is regulated by glycogen synthase and
glycogen phosphorylase
b) is located in a cytoplasm
c) is regulated by insulin
d) proceeds on reducing ends of glycogen
molecule
Metabolism of glycogen
The figure is found at http://www.kumc.edu/research/medicine/biochemistry/bioc800/car02fra.htm (Jan 2007)
During glycogen synthesis
(= glycogenesis)
a) Glc-6-P is transformed to UDP-6-glc
b) glycogen synthase participates in a formation
of both (1→4) and (1→6) glycosidic bonds
c) a macroergic phosphate is consumed
d) is glycogen synthase activated by glucagon
During glycogen synthesis
(= glycogenesis)
a) Glc-6-P is transformed to UDP-6-glc
b) glycogen synthase participates in a formation
of both (1→4) and (1→6) glycosidic bonds
c) a macroergic phosphate is consumed
d) is glycogen synthase activated by glucagon
The figure is found at http://www.kumc.edu/research/medicine/biochemistry/bioc800/car02fra.htm (Jan 2007)
During degradation of glycogen within cells
(= glycogenolysis)
a) (1→6) glycosidic bonds are split by glycogen
phosphorylase
b) glucose is transfered to phosphate: glc-1-P
is formed as a product of the degradation
c) (1→4) bonds are split hydrolytically
d) 1 ATP is consumed if 1 glc is released
During degradation of glycogen within cells
(= glycogenolysis)
a) (1→6) glycosidic bonds are split by glycogen
phosphorylase
b) glucose is transfered to phosphate: glc-1-P
is formed as a product of the degradation
c) (1→4) bonds are split hydrolytically
d) 1 ATP is consumed if 1 glc is released
The figure is found at http://www.kumc.edu/research/medicine/biochemistry/bioc800/car02fra.htm (Jan 2007)
If glycogenolysis is followed by glycolysis
a) the net gain of the anaerobic glycolysis is
3 ATP
b) the process is called gluconeogenesis
c) both the cytoplasmatic and mitochondrial
enzymes participate in the reactions
d) oxaloacetate is formed as an intermediate
If glycogenolysis is followed by glycolysis
a) the net gain of the anaerobic glycolysis is
3 ATP
b) the process is called gluconeogenesis
c) both the cytoplasmatic and mitochondrial
enzymes participate in the reactions
d) oxaloacetate is formed as an intermediate
glycogen
Pi
glucose
ATP
ADP
The figure is found at http://www.kumc.edu/research/medicine/biochemistry/bioc800/car02fra.htm (Jan 2007)
Regulation of glycogen metabolism
regulatory enzyme
activation
 glucagon,
glykogen
adrenaline
phosphorylase
(phosphorylation)
(glycogen degradation)
inhibition
  ATP / AMP
 glucose-6-phosphate
 glucose
  ATP / AMP
 Ca2+ (muscle)
glykogen synthase
(glycogen synthesis)
 insulin (induction)
 glucose-6-phosphate
 glucagon,
adrenaline
(phosphorylation)
Pentose cycle
(= Hexose MonoPhosphate Pathway, HMPP)
a) is located in a cytoplasm
b) includes direct oxidation of glucose
monophosphate
c) is a shunt of glycolysis (products of HMPP
can enter glycolysis)
d) produces pentoses
Pentose cycle
(= Hexose MonoPhosphate Pathway, HMPP)
a) is located in a cytoplasm
b) includes direct oxidation of glucose
monophosphate
c) is a shunt of glycolysis (products of HMPP
can enter glycolysis)
d) produces pentoses
The figure is found at http://www.richmond.edu/~jbell2/14F34.JPG (Dec 2006)
Choose enzymes of HMPP
a) transketolase
b) transaminase
c) glucose-6-phosphate dyhydrogenase
(glc-6-P DH)
d) pyruvate carboxylase
Choose enzymes of HMPP
a) transketolase
b) transaminase
c) glucose-6-phosphate dyhydrogenase
(glc-6-P DH) = regulatory enzyme
d) pyruvate carboxylase
Pentose cycle
a) produces NADPH which can be oxidized in a
respiratory chain → energy is produced
b) generates saccharides used in a glycoprotein
synthesis
c) forms ribose-5-phosphate a substrate of
nucleic acids synthesis
d) forms fru-6-P and glyceraldehyde-3-P which
can enter glycolysis or gluconeogenesis
Pentose cycle
a) produces NADPH which can be oxidized in a
respiratory chain → energy is produced
b) generates saccharides used in a glycoprotein
synthesis
c) forms ribose-5-phosphate a substrate of
nucleic acids synthesis
d) forms fru-6-P and glyceraldehyde-3-P which
can enter glycolysis or gluconeogenesis
If NADPH accumulates
a) oxidative part of HMPP is inhibited
b) ribose-5-phosphate can not be synhesized
c) glc-6-P dehydrogenase is activated
d) the reversible reactions of the HMPP can
only proceed
If NADPH accumulates
a) oxidative part of HMPP is inhibited
b) ribose-5-phosphate can not be synhesized
c) glc-6-P dehydrogenase is activated
d) the reversible reactions of the HMPP can
only proceed
I
R
R
E
V
E
R
S
I
B
L
E
The figure is found at http://web.indstate.edu/thcme/mwking/pentose-phosphate-pathway.html (Dec 2006)
synthesis of
nucleotides
R
E
V
E
R
S
I
B
L
E
intermediates of
glycolysis
The figure is found at http://web.indstate.edu/thcme/mwking/pentose-phosphate-pathway.html (Dec 2006)
Regulation of HMPP
• on the level of substrates availability and
products consumption
 NADPH / NADP+
reaction using NADP+ are inhibited by lack
of the coenzyme
Fructose
a) is metabolized mainly in the liver
b) can be transformed to fru-6-P by fructokinase
c) can be formed from sorbitol as well
d) can be transformed to glucose
Fructose
a) is metabolized mainly in the liver
b) can be transformed to fru-6-P by fructokinase
c) can be formed from sorbitol as well
d) can be transformed to glucose
Metabolism of fructose in the liver
glycolysis or gluconeogenesis
The figure is found at http://web.indstate.edu/thcme/mwking/glycolysis.html (Jan 2007)
The figure was adopted from Devlin, T. M. (editor): Textbook of Biochemistry with Clinical Correlations, 4th ed.
Wiley-Liss, Inc., New York, 1997. ISBN 0-471-15451-2
When Fru is converted to Fru-1-P
a) it can be split by an aldolase to glyceraldehyde
and dihydroxyacetone phosphate
b) is fructose metabolised in glycolysis faster
then glucose
c) glyceraldehyde made by spliting of fru-1-P can
be converted to glycerol
d) glucokinase can be activated by fru-1-P
When Fru is converted to Fru-1-P
a) it can be split by an aldolase to glyceraldehyde
and dihydroxyacetone phosphate
b) is fructose metabolised in glycolysis faster
then glucose
c) glyceraldehyde made by spliting of fru-1-P can
be converted to glycerol
d) glucokinase can be activated by fru-1-P
Glucose can be converted to
a) galactose: glc-6-P → gal-6-P
b) fructose: glc → glucitol → fru
c) glucuronic acid: UDP-glc + 2 NAD+
→ UDP-glukuronate + 2 NADH+H+
d) ribose: glc-6-P → → ribulose-5-P → rib-5-P
Glucose can be converted to
a) galactose: glc-6-P → gal-6-P
b) fructose: glc → glucitol → fru
c) glucuronic acid: UDP-glc + 2 NAD+
→ UDP-glukuronate + 2 NADH+H+
d) ribose: glc-6-P → → ribulose-5-P → rib-5-P
Metabolism of galactose
epimerization
proceeds on
the level of
UDPderivatives
The figure is found at http://web.indstate.edu/thcme/mwking/glycolysis.html (Jan 2007)
The figure is found at http://www.kumc.edu/research/medicine/biochemistry/bioc800/car02fra.htm (Jan 2007)