Metabolic processes are the chemical reactions that occur in the body and include both anabolism and catabolism. Anabolism involves building larger molecules from smaller ones and requires energy, while catabolism breaks down larger molecules into smaller ones and releases energy. Enzymes control the rates of metabolic reactions by lowering the activation energy needed for the reactions and are specific to certain substrates due to the shape of their active sites.

1. METABOLIC
PROCESSES
CHARILYN D. DELA CRUZ
1

2. Introduction
2
• Metabolic processes – all chemical reactions that occur
in the body
There are two (2) types of metabolic reactions:
• Anabolism
• Larger molecules
are made from
smaller ones
• Requires energy
• Catabolism
• Larger molecules
are broken down into
smaller ones
• Releases energy

3. Anabolism 3
• Anabolism provides the materials needed for cellular
growth and repair
• Dehydration synthesis
• Type of anabolic process
• Used to make polysaccharides, triglycerides, and proteins
• Produces water
CH2OH
H
H
OH
O
H OH
Monosaccharide +
HHO
H
OH
H
H
OH
O
H OH
Monosaccharide
HHO
H
OH
H
H
OH
O
H OH
Disaccharide
H2O
Water+
HHO
H H
H
OH
O
H OH
HO
H
OH
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CH2OH CH2OH CH2OH

4. Amino acid
N
H
H
C C
H
R
Dipeptide molecule ++
Peptide
bond
Amino acid
N
H
H
C C
H
H
H
R
H
O
N
H
H
C C
H
R
H
O
N
H
C C OH
R
H
O
O
N
H
H
C C
H
R
N
H
C C OH
R
H
O
O
Water
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O O
H2O
Anabolism
4
H C
H
Glycerol 3 fatty acid molecules+
OH HO
H C OH HO
H C
C
C
COH HO
H
O
O
C
C
C
O
O
O
H C
H
Fat molecule (triglyceride) +
H C
H C O
O
O
H
3 water
molecules
(CH2)14 CH3
(CH2)14 CH3
(CH2)14 CH3
(CH2)14 CH3
(CH2)14 CH3
(CH2)14 CH3
H2O
H2O
H2O
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O

5. Catabolism 5
• Catabolism breaks down larger molecules into smaller ones
• Hydrolysis
• A catabolic process
• Used to decompose carbohydrates, lipids, and proteins
• Water is used to split the substances
• Reverse of dehydration synthesis
CH2OH
H
H
OH
O
H OH
Monosaccharide +
HHO
H
OH
H
H
OH
O
H OH
Monosaccharide
HHO
H
OH
H
H
OH
O
H OH
Disaccharide
H2O
Water+
HHO
H H
H
OH
O
H OH
HO
H
OH
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
CH2OH CH2OH CH2OH

6. Catabolism 6
Amino acid
N
H
H
C C
H
R
Dipeptide molecule ++
Peptide
bond
Amino acid
N
H
H
C C
H
H
H
R
H
O
N
H
H
C C
H
R
H
O
N
H
C C OH
R
H
O
O
N
H
H
C C
H
R
N
H
C C OH
R
H
O
O
Water
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
O O
H2O
H C
H
Glycerol 3 fatty acid molecules+
OH HO
H C OH HO
H C
C
C
COH HO
H
O
O
C
C
C
O
O
O
H C
H
Fat molecule (triglyceride) +
H C
H C O
O
O
H
3 water
molecules
(CH2)14 CH3
(CH2)14 CH3
(CH2)14 CH3
(CH2)14 CH3
(CH2)14 CH3
(CH2)14 CH3
H2O
H2O
H2O
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O

7. Control of Metabolic Reactions 7
• Enzymes
• Control rates of metabolic reactions
• Lower activation energy needed to start reactions
• Most are globular proteins with specific shapes
• Not consumed in chemical reactions
• Substrate specific
• Shape of active site determines substrate
Product molecule
Active site
(a) (b) (c)
Substrate molecules
Unaltered
enzyme
molecule
Enzyme-substrate
complex
Enzyme
molecule
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8. 8
Enzymes are globular proteins that promote chemical
reactions by lowering the activation energy required to
start the reaction and enhancing the reaction rate.
They are catalysts that do not get chemically changed in
the reaction themselves .
Since they are not consumed by the reaction, they are
needed only in very small quantities.
Enzymes are specific and act only on particular
substrates. There are enzymes that make bonds and
synthesize molecules and there are those enzymes that
break bonds and degrade molecules into smaller
molecules.

9. Enzyme Action
9
• Metabolic pathways
• Series of enzyme-controlled reactions leading to formation
of a product
• Each new substrate is the product of the previous reaction
• Enzyme names commonly:
• Reflect the substrate
• Have the suffix – ase
• Examples: sucrase, lactase, protease,
lipase
Substrate
1
Enzyme A Substrate
2
Enzyme B Substrate
3
Enzyme C Substrate
4
Enzyme D
Product
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10. Cofactors and Coenzymes
10
• Cofactors
• Make some enzymes active
• Non-protein component
• Organic Ions or coenzymes such as zinc, copper,
calcium, or iron.
• Coenzymes
• Organic molecules that act as cofactors
• Small organic molecules that are often vitamins or
derived from vitamins.
Enzymes are often inactive until combining with cofactors
or coenzymes.

11. Factors That Alter Enzymes
11
• Factors that alter enzymes:
• Heat
• Radiation
• Electricity
• Chemicals
• Changes in pH

12. Regulation of Metabolic
Pathways
12
• Limited number of regulatory enzymes
• Negative feedback
Inhibition
Substrate
1
Substrate
2
Enzyme B Substrate
3
Enzyme C Substrate
4
Enzyme D
Product
Rate-limiting
Enzyme A
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13. 13
Important Points in Chapter 4:
Outcomes to be Assessed
4.1: Introduction
 Define metabolism.
 Explain why protein synthesis is important.
4.2: Metabolic Processes
 Compare and contrast anabolism and catabolism.
 Define dehydration synthesis and hydrolysis.
4.3: Control of Metabolic Reactions
 Describe how enzymes control metabolic reactions.
 List the basic steps of an enzyme-catalyzed reaction.
 Define active site.