Download Ch 4: Cellular Metabolism

Carbohydrate Metabolism
Aulanni’am
Biochemistry Laboratory
Chemistry Departement
Brawijaya University
Aulani "Biokimia" Presentation 3
Aulani "Biokimia" Presentation 3
Carbohydrates

Carbohydrates are the most abundant organic molecules in
nature
 Photosynthesis energy stored in carbohydrates;
 Carbohydrates are the metabolic precursors of all
other biomolecules;
 Important component of cell structures;
 Important function in cell-cell recognition;
 Carbohydrate chemistry:
 Contains at least one asymmetric carbon center;
 Favorable cyclic structures;
 Able to form polymers
Aulani "Biokimia" Presentation 3
Carbohydrate Nomenclature

Carbohydrate Classes:
 Monosaccharides (CH2O)n
 Simple sugars, can not be broken down further;


Oligosaccharides
 Few simple sugars (2-6).
Polysaccharides
 Polymers of monosaccharides
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Carbohydrate Nomenclature

Monosaccharide (carbon numbers 3-7)

Aldoses
1
 Contain aldehyde
2
 Name: aldo-#-oses (e.g., aldohexoses) 3
4
Memorize all aldoses in Figure ?
5
6

Ketoses
 Contain ketones
 Name: keto-#-oses (ketohexoses)
Aulani "Biokimia" Presentation 3
CHO
H
OH
H
OH
H
OH
H
OH
CH2OH
1
CHO
2
H
O
3
H
OH
4
H
OH
5
6
H
OH
CH2OH
Monosaccharide Structures
Axis
a
Conformation of monosaccharide
e
a O
a
a
H
H
OH
e
e
e
a
Chair
CH2OH
OH
O
H
a
a
e
e
H
HO 2HC
HO
HO
OH
HO
H
OH
H
H
Axis
e
e
Oe
e
a
a
a
Boat
OH
H
H
Conformation of glucose
OH
-D-glucopyranose
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Disaccharides




Simplest oligosaccharides;
Contain two monosaccharides linked by a
glycosidic bond;
The free anomeric carbon is called reducing end;
The linkage carbon on the first sugar is always
C-1. So disaccharides can be named as sugar(a,b)-1,#-sugar, where a or b depends on the
anomeric structure of the first sugar. For
example, Maltose is glucose-a-1,4-glucose.
Aulani "Biokimia" Presentation 3
Structures of Disaccharides
Note the linkage and reducing ends
O
OH 5
OH
4
1
3
OH
O 4
3
2
HOH
1
1
OH 3
4
OH 3
OH
1
2
O
3
O
OH 3
2
Maltose (glucose--1,4-glucose)
4
OH
1
CH2OH
O
5
HOH
1
OH
2
OH
6 CH2OH
OH
4
HOH
1
Cellobiose (glucose--1,4-glucose)
6 CH2OH
5
3
OH
Lactose (galactose--1,4-glucose)
O
OH
O 4
2
OH
6 CH2OH
O
5
OH
4
2
OH
5
O
5
O
5
6 CH2OH
6 CH2OH
6 CH2OH
6 CH2OH
OH
1
2
O
2
O
3
OH
OH 5
CH2OH
46
OH
Sucrose (glucose--1,2-froctose)
Aulani "Biokimia" Presentation 3
no reducing end
Polysacchrides





Also called glycans;
Starch and glycogen are storage molecules;
Chitin and cellulose are structural molecules;
Cell surface polysaccharides are recognition molecules.
Glucose is the monosaccharides of the following
polysacchrides with different linkages and banches
 a(1,4), starch (more branch)
 a(1,4), glycogen (less branch)
 a(1,6), dextran (chromatography resins)
 b(1,4), cellulose (cell walls of all plants)
 b(1,4), Chitin similar to cellulose, but C2-OH is
replaced by –NHCOCH3 (found in exoskeletons of
crustaceans, insects, spiders)
Aulani "Biokimia" Presentation 3
Overview of Glucose Catabolism

Cells catabolize organic molecules and make ATP
two ways:
 Substrate-Level Phosphorylation
 Glycolysis
 Krebs (TCA) Cycle
 Oxidative Phosphorylation
 Electron Transport Chain
Aulani "Biokimia" Presentation 3
Overview of Glucose Catabolism
Aulani "Biokimia" Presentation 3
Overview of Glucose Catabolism

Glycolysis
 Biochemical pathway that
produces ATP by
substrate-level
phosphorylation.
 Yields a net of two
ATP molecules for
each molecule of
glucose catabolized.
 Every living creature is
capable of carrying out
glycolysis.
 Most present-day
organisms can extract
considerably more energy
from glucose through
aerobic respiration.
•Net reaction
C 6 H12 O 6  2Pi  2ADP  2 NAD  
2C 3 H 4 O 3  2ATP  2 NADH  H  
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Glucose priming
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Cleavage and
rearrangement
P
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P
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Krebs Cycle


After pyruvate has been
oxidized, acetyl- CoA feeds
into the Krebs cycle.
Krebs cycle is the next step
of oxidative respiration and
takes place in mitochondria.
Occurs in three stages:
 Acetyl-CoA binds a fourcarbon molecule and
produces a six-carbon
molecule.
 Two carbons are removed
as CO2.
 Four-carbon starting
material is regenerated.

Cycle is also known as
 Tricarboxylic acid
(TCA) cycle
 Citric acid cycle
COOH
CH2
HO C COOH
CH2
COOH
citric acid
Aulani "Biokimia" Presentation 3
Aerobic Respiration



The pyruvic acid formed by glycolysis enters interior of
mitochondria.
Converted by coenzyme A to 2 molecules of acetyl CoA and 2 C02.
Acetyl CoA serves as substrate for mitochondrial enzymes in the
aerobic pathway.
Aulani "Biokimia" Presentation 3
Aulani "Biokimia" Presentation 3
pyruvate (3C)
CO2
acetyl coenzyme A (2C)
oxaloacetate (4C)
FADH
citrate (6C)
NADH
NADH
GTP
CO2
-ketoglutarate (5C)
succinate (4C)
CO2
NADH
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Aulani "Biokimia" Presentation 3
Aulani "Biokimia" Presentation 3
Krebs Cycle


Generates two ATP molecules per molecule of
glucose.
Generates many energized electrons which can be
directed to the electron transport chain to drive
synthesis of more ATP:
 6 NADH per molecule of glucose
 2 FADH2 per molecule of glucose
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Aulani "Biokimia" Presentation 3
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Glycolysis
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
KREBS CYCLE




Takes place in Mitochondrion when oxygen is present
Pyruvic acid from glycolysis is trimmed to a 2 carbon compound
 Remaining carbon from glucose => CO2
Hydrogens transferred
 NAD+ => NADH
 FAD => FADH
Products of kreb cycle
 3 NADHs
 1 FADH2
 2 ATP
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The Cori Cycle



The reconversion of lactic acid to pyruvate
sees the removal of fatiguing lactate from
the site of production.
This forms the theoretical basis for the
cool-down.
As the glycolysis pathway is reversible
lactic acid can eventually be anabolised into
glucose and stored in the liver, muscles or
blood.
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Electron Transport System
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Electron Transport System
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Energy

Capacity to perform work.

Two examples:
1. Kinetic energy
2. Potential energy
Aulani "Biokimia" Presentation 3
Kinetic Energy

Energy in the process of doing work.

Energy of motion.

Examples:
1. Heat
2. Light energy
SUN
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Potential Energy



Energy that matter occupies because of it’s location,
arrangement, or position.
Energy of position.
Examples:
1. Water behind a dam
2. Chemical energy (gas)
Aulani "Biokimia" Presentation 3
GAS
Question:

What is ATP?
Answer:


adenosine triphosphate (ATP)
Components:
1. adenine:
nitrogenous base
2. ribose: five carbon sugar
3. phosphate group: chain of three
adenine
phosphate group
P
ribose
Aulani "Biokimia" Presentation 3
P
P
Answer:



Works by the direct chemical transfer of a
phosphate group.
This is called “phosphorylation”.
The exergonic hydrolysis of ATP is coupled with the
endergonic processes by transferring a phosphate
group to another molecule.
Aulani "Biokimia" Presentation 3
Hydrolysis of ATP

ATP + H2O  ADP + P (exergonic)
Adenosine triphosphate (ATP)
P
P
P
Hydrolysis
(add water)
P
P
+
P
Adenosine diphosphate (ADP)
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Dehydration of ATP
ADP + P  ATP + H2O (endergonic)
Adenosine triphosphate (ATP)
P
P
P
Dehydration synthesis
(remove water)
P P +
P
Adenosine diphosphate
(ADP)
Aulani "Biokimia" Presentation 3
Aulani "Biokimia" Presentation 3