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CHAPTER 24: Carbohydrate,
Lipid, & Protein Metabolism
General, Organic, & Biological Chemistry
Janice Gorzynski Smith
CHAPTER 24: Carbohydrate, Lipid, & Protein
Metabolism
Learning Objectives:
 Role in Metabolism of fatty acid oxidation, glycolysis, & Amino acid
catabolism
 Reactions catalyzed by: kinase, isomerase, dehydrogenase, decarboxylase,
carboxylase
 Glycolysis: steps & net reaction
 Pyruvate conversion to acetyl Coenzyme A
 Gluconeogenesis: steps in synthesis of glucose
 Catabolism of Triacylglycerols: beta-oxidation
 Synthesis of ketone bodies: ketogenesis
 Catabolism of Amino acids:
 transamination & oxidative deamination
 Ketogenic vs glucogenic amino acid catabolism
CH 24 Homework:
End of Chapter problems: 30, 36, 38, 42, 47, 52, 58, 60, 64, 68, 71, 75,
76, 78, 80, 82, 96, 98
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
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Metabolism
Step 2 of Metabolism
• Fatty acid oxidation
• Glycolysis
• Amino Acid
Catabolism
 All lead to the
production of Acetyl CoA
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
3
Metabolism
Step 2 of Metabolism
•In the catabolism of carbohydrates, glycolysis
converts glucose into pyruvate, which is then
metabolized into acetyl CoA.
Metabolism
Step 2 of Metabolism
•In the catabolism of lipids, fatty acids are converted
into thioesters and then cleaved into many
acetyl CoA units.
Metabolism
Step 2 of Metabolism
•Amino acids are usually reassembled into new
proteins.
•Since excess amino acids are not stored in the
body, they can also be catabolized for energy.
•The amino groups (NH2) are converted to urea
[(NH2)2C=O], which is excreted in urine.
Metabolism
Step 2 of Metabolism: Urea Cycle
http://www.t3portal.org/T3_Portal_v1/!SSL!/WebHelp/ales_vancura Catabolism_of_amino_acids.htm
Biochemical
Rxns
Common Enzymes
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
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Biochemical
Rxns
Common Enzymes: Example
•The transfer of a phosphate unit from ATP to the
fructose 6-phosphate molecule is catalyzed by
a kinase enzyme.
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
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Glycolysis
Definition
•Glycolysis is a linear, 10-step
anaerobic pathway that converts
glucose into two molecules of
pyruvate.
•Steps [1] – [5] comprise the energy
investment phase, where 2 ATP
molecules are hydrolyzed.
•The 6-carbon glucose molecule is
converted into two 3-carbon segments.
•Steps [6] – [10] comprise the energygenerating phase, producing 1 NADH
and 2 ATPs for each pyruvate formed.
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
10
Glycolysis
Energy Investment
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
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Glycolysis
Energy Generation
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
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Glycolysis
Step 1
•Step [1] begins with the
phosphorylation of glucose into
glucose 6-phosphate, using an ATP
and a kinase enzyme.
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
13
Glycolysis
Step 2
•Step [2] isomerizes
glucose 6-phosphate to
fructose 6-phosphate
with an isomerase enzyme.
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
14
Glycolysis
Step 3
•Step [3] is the
phosphorylation of
fructose 6-phosphate into
fructose 1,6-bisphosphate
with a kinase enzyme.
Steps [1-3] add 2 phosphate
groups and isomerize a 6membered ring into a 5membered ring. Energy is
stored as 2 ATP molecules.
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
15
Glycolysis
Step 4
•Step [4] cleaves the fructose ring into a dihydroxyacetone phosphate and a glyceraldehyde 3-phosphate.
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
16
Glycolysis
Step 5
•Step [5] isomerizes the dihydroxyacetone phosphate
into another glyceraldehyde 3-phosphate.
•Thus, the first phase of glycolysis converts
glucose into 2 glyceraldehyde 3-phosphate units.
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
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Glycolysis
Step 6
•In step [6] the aldehyde end of the molecule
is oxidized and phosphorylated by a dehydrogenase
enzyme and NAD+; this produces 1,3-bisphosphoglycerate and NADH.
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
18
Glycolysis
Step 7
•In step [7], the phosphate group is transferred
onto an ADP with a kinase enzyme, forming
3-phosphoglycerate and ATP.
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
19
Glycolysis
Step 8
•In step [8], the phosphate group is isomerized to
a new position in 2-phosphoglycerate.
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
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Glycolysis
Step 9
•In step [9], water is lost to form phosphoenolpyruvate.
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
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Glycolysis
Step 10
•In step [10], the phosphate is transferred to an ADP,
yielding pyruvate and ATP with a kinase enzyme.
•The 2 glyceraldehyde 3-phosphate units
are converted into 2 pyruvate units in
Phase two of glycolysis.
•Overall, the energy-generating phase
forms 2 NADHs and 4 ATPs.
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
22
Glycolysis
Overall Reaction
•2 ATPs are used in phase one of
glycolysis, and 4 ATPs are made in
phase two of glycolysis.
•The net result is the synthesis of 2
ATPs from glycolysis
•The 2 NADHs formed are made in
the cytoplasm and must be
transported to the mitochondria to
join the electron transport chain and
make ATP.
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
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Glycolysis
Pyruvate
Pyruvate can be converted into three possible
products depending on the conditions and the
organism.
under aerobic
conditions
under anaerobic
conditions
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
in fermentation
by microorganisms
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Glycolysis
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
ATP Yield
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Glycolysis
ATP Yield
2 x 2.5 ATP =
5 ATP
2 x 2.5 ATP =
5 ATP
2 ATP
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
6 x 2.5 =
15 ATP
2 x 1.5 =
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3 ATP
Gluconeogenesis
Definition
•Gluconeogenesis is the synthesis of glucose from
noncarbohydrate sources—lactate, amino acids,
or glycerol.
•Gluconeogenesis is an anabolic pathway since
it results in the synthesis of larger molecules from
smaller ones.
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
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Gluconeogenesis
Cori Cycle
Smith, Janice Gorzynski. General, Organic,
& Biological Chemistry 2nd Ed.
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