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Bahan kuliah Biokimia dengan judul Metabolisme Karbohidrat
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METABOLISME KARBOHIDRAT
Carbohydrate metabolism ICarbohydrate metabolism I
Carbohydrates computing
Presentation copyright © 2002 David A Bender and some images copyright © 2002 Taylor & Francis Ltd
Carbohydrates
composed of carbon, hydrogen and oxygen only
in the ratio C6H12O6
Carbohydrates
• Contain carbon, hydrogen, and oxygen• Their major function is to supply a source of
cellular food• Examples:
– Monosaccharides or simple sugars
Figure 2.13a
Carbohydrates
• Disaccharides or double sugars
Figure 2.13b
Carbohydrates
• Polysaccharides or polymers of simple sugars
Figure 2.13c
Nutritionally important disaccharides - 1
computing
Presentation copyright © 2002 David A Bender and some images copyright © 2002 Taylor & Francis Ltd
Nutritionally important disaccharides
-1,4-binding -1,4-binding
Figuur 11. De -1,4-binding en de -1,4-binding die in polysacchariden voorkomen.
-1,6-binding
Figuur 12. De -1,6-binding zoals deze in amylopectine voorkomt.
Nutritionally important disaccharides - 2
computing
Presentation copyright © 2002 David A Bender and some images copyright © 2002 Taylor & Francis Ltd
Nutritionally important disaccharides
isomaltosemaltose (glucosyl-glucose)
OOH
OH
OH
CH2OHCH2OH
O
OH
OHO
O H
H
CH2OH
O
OH
OHO
O
CH2
O OH
OH
OHO
H
Branched structure of starch and glycogen
computing
Presentation copyright © 2002 David A Bender and some images copyright © 2002 Taylor & Francis Ltd
The branched structure of starch and glycogen
1 6 links: branch points inamylopectin and glycogen O
OH
OH
CH2OH
OOH
OH
CH2OH
O O
OOH
OH
CH2OH
OOH
OH
CH2
O O O
O
O
OOH
OH
CH2OH
O
OOH
OH
CH2OH
Hydrolysis of starch by amylase
computing
Presentation copyright © 2002 David A Bender and some images copyright © 2002 Taylor & Francis Ltd
Hydrolysis of starch by alpha-amylase in saliva and pancreatic juice results in formation of dextrins, then:
glucose
maltose
isomaltose
1 6 links: branch points inamylopectin and glycogen O
OH
OH
CH2OH
OOH
OH
CH2OH
O O
OOH
OH
CH2OH
OOH
OH
CH2
O O O
O
O
OOH
OH
CH2OH
O
OOH
OH
CH2OH
Major types of non-starch polysaccharides
computing
Presentation copyright © 2002 David A Bender and some images copyright © 2002 Taylor & Francis Ltd
cellulose - glucose polymer linked 1 4
O
OH
OH
CH2OH
O
OOH
OH
CH2OH
OOH
OH
CH2OH
OOH
OH
CH2OH
O O O O
chitin - N-acetylglucosamine polymer linked 1 4
O
OH
CH2OH
O
OOH
CH2OH
OOH
CH2OH
OOH
CH2OH
O O O O
HN C CH3
O
HN C CH3
O
HN C CH3
O
HN C CH3
O
pectin - galacturonic acid polymer linked 1 4, partially methylated; some glactose and/or arabinose branches
O
OH
OH
COOH
OOH
OH
COOH
OOH
OH
CO CH3
OOH
OH
COOH
O O O OO
O CH2
OH
OH
O
HOCH2
O CH2
OH
OH
HOCH2
O CH2
OH
OH
HOCH2
O CH2
OH
OH
HOCH2
O
O
O
O
inulin - fructose polymer linked 2 1
The major types of non-starch polysaccharide
Glycaemic and non-glycaemic carbohydrates - 1
computing
Presentation copyright © 2002 David A Bender and some images copyright © 2002 Taylor & Francis Ltd
Dietary starches can be classified as:
rapidly digested (hence high glycaemic index) slowly digested (lower glycaemic index)
not all digested in small intestine amylose is hydrolysed more slowly than amylopectin
resistant starch (low glycaemic index) only hydrolysed to a limited extent in small intestine
starch may be resistant because: it is crystalline and resistant to amylases it is enclosed in plant cell walls that are not digested
some resistant starch is fermented by bacteria in the large intestine
Glycaemic and non-glycaemic carbohydrates
Glycaemic indexThe extent to which a test dose of a carbohydrate increases blood glucosecompared with an equivalent amount of glucose
Glucose
Glucose-6-P
Pyruvate
Hexokinase
PentosePhosphateShunt
glycolysis
Carbohydrates• Serve as primary source of energy in the cell• Central to all metabolic processes
Glc-1- phosphate
glycogen
Cytosol - anaerobic
Pyruvatecytosol
Aceytl CoAmitochondria (aerobic)
Krebscycle
Reducingequivalents
OxidativePhosphorylation(ATP)
AMINOACIDS
FATTY ACIDS
Glycogen synthase (active)
OHPGlycogen synthase (inactive)
Glycogen formation
Glycogen synthase kinase (active)
OH
IRinsulin
P
PProtein Kinase B (active)
Protein Kinase B (inactive)
OH
P Glycogen synthase kinase (inactive)
Overview of metabolismcomputing
Presentation copyright © 2002 David A Bender and some images copyright © 2002 Taylor & Francis Ltd
glucose-6-phosphate glucoseglycogen( 6 carbons)
(3 carbons)lactate
acetyl CoA
pyruvate
CO2
(2 carbons)fatty acids
triacylglycerols
ketones
oxaloacetate citrate
CO2
CO2
CITRIC ACID CYCLE
FATTY ACID SYNTHESIS
FATTY ACID OXIDATIONKETOGENESIS
GL
UC
ON
EO
GE
NE
SIS
GLYCOGEN SYNTHESIS
GLYCOGENOLYSIS
LIPASE
GL
YC
OL
YS
IS
Glycolysis pathway
[Tri-carboxylic Acid (TCA) cycle]
