1. Chapter 4 Cellular Metabolism
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2. Objectives (page 76) 4.1.1 Briefly explain the role of metabolism
4.2.1 Compare and contrast anabolism and catabolism
4.3.3 Describe how enzymes control metabolic reactions
4.4.5 Explain how cellular respiration releases chemical energy
4.4.6 Describe how energy in the form of ATP becomes available for cellular activities

3. 4.1: Introduction
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

4. 4.3: Control of Metabolic Reactions
Enzymes
Control rates of metabolic reactions
Lower activation E needed to start reactions
Most are globular proteins with specific shapes
Not consumed in chemical reactions
Substrate specific
Shape of active site determines substrate
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Substrate molecules
Product molecule
Active site
Enzyme
molecule
Enzyme-substrate
complex
Unaltered
enzyme
molecule
(a)
(b)
(c)

5. Factors That Alter Enzymes
Heat
Radiation
Electricity
Chemicals
Changes in pH

6. 4.4: Energy for Metabolic Reactions
Energy is the capacity to change something; it is the ability to do work
Common forms of energy:
Heat
Light
Sound
Electrical energy
Mechanical energy
Chemical energy

7. ATP Molecules Each ATP molecule has three parts:
An adenine molecule
A ribose molecule
Three phosphate molecules in a chain
Third phosphate attached by high-E bond
When the bond is broken, E is transferred
When the bond is broken, ATP becomes ADP
ADP becomes ATP through phosphorylation
Phosphorylation requires energy release from cellular respiration
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. P P P
Energy transferred
from cellular
respiration used
to reattach
phosphate
Energy transferred
and utilized by
metabolic
reactions when
phosphate bond
is broken P P P P

8. 4.5: Cellular Respiration
Occurs in a series of reactions:
Glycolysis
“Prep” steps or intermediate steps
Citric acid cycle (aka TCA or Kreb’s Cycle)
Electron transport system (ETC)

9. Cellular Respiration Produces: Includes: Carbon dioxide Water
ATP (chemical energy)
Heat
Includes:
Anaerobic reactions (without O2) - produce little ATP
Aerobic reactions (requires O2) - produce most ATP

10. Glycolysis Breaks down glucose into 2 pyruvic acid molecules
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Phase 1
priming
Glucose
Breaks down glucose into 2 pyruvic acid molecules
Occurs in cytosol
Anaerobic phase of cellular respiration
Yields two ATP molecules per glucose molecule
Carbon atom P
Phosphate 2
ATP
2 ADP
Fructose-1,6-diphosphate P P
Phase 2
cleavage
Dihydroxyacetone
phosphate
Glyceraldehyde
phosphate P P
Phase 3
oxidation and
formation of
ATP and release
of high energy
electrons P
2 NAD+
4 ADP
2 NADH + H+ 4
ATP
2 Pyruvic acid O2 O2
2 NADH + H+
2 NAD+
To citric acid cycle
and electron transport
chain (aerobic pathway)
2 Lactic acid

11. Anaerobic Reactions If oxygen is not available:
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If oxygen is not available:
Pyruvic acid is converted to lactic acid
LA = 
Phase 1
priming
Glucose
Carbon atom P
Phosphate 2
ATP
2 ADP
Fructose-1,6-diphosphate P P
Phase 2
cleavage
Dihydroxyacetone
phosphate
Glyceraldehyde
phosphate P P
Phase 3
oxidation and
formation of
ATP and release
of high energy
electrons P
2 NAD+
4 ADP
2 NADH + H+ 4
ATP
2 Pyruvic acid O2 O2
2 NADH + H+
2 NAD+
To citric acid cycle
and electron transport
chain (aerobic pathway)
2 Lactic acid

12. Aerobic Reactions If oxygen is available:
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If oxygen is available:
Pyruvic acid is used to produce acetyl CoA
Citric acid cycle begins
Electron transport system functions
Glucose
High energy
electrons (e–) and
hydrogen ions (H+) 2
ATP
Pyruvic acid
Pyruvic acid
Cytosol
Mitochondrion
High energy
electrons (e–) and
hydrogen ions (h+)
CO2
Acetyl CoA
Oxaloacetic
acid
Citric acid
High energy electrons (e–) and hydrogen ions (H+)
2 CO 2 2
ATP
Electron transport chain
32-34
ATP O 2 2e –
+ 2H + H 2 O

13. Citric Acid Cycle One ATP 3 NADH 1 FADH2 Two CO2 produced
Begins when acetyl CoA combines with oxaloacetic acid to produce citric acid
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Pyruvic acid from glycolysis
Cytosol
Carbon atom + P
Phosphate
NAD CO 2
Mitochondrion
CoA
Coenzyme A
NADH + H +
Acetic acid
CoA
Acetyl CoA
For each citric acid molecule:
One ATP
3 NADH
1 FADH2
Two CO2 produced
(replenish molecule)
Oxaloacetic acid
Citric acid
(finish molecule)
(start molecule)
NADH + H +
CoA
NAD +
Malic acid
Isocitric acid
NAD +
Citric acid cycle CO 2
NADH + H +
Fumaric acid
-Ketoglutaric acid CO 2
CoA
FADH 2
NAD +
FAD
NADH + H +
Succinic acid
Succinyl-CoA
CoA
ADP + P
ATP

14. Electron Transport System
NADH and FADH2 carry electrons to the ETS (ETC)
ETS is a series of electron carriers located in cristae of mitochondria
Energy from electrons is eventually transferred to ATP synthase
ATP synthase catalyzes the phosphorylation of ADP to ATP
Oxygen removes excess electrons and water is formed
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ATP synthase
ADP + P
ATP
Energy
NADH + H+
Energy
2H+
+ 2e–
FADH2
Energy
NAD+
2H+
+ 2e–
FAD
Electron transport chain
2e–
2H+ O 2
H2O

15. Summary of Cellular Respiration
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Glucose
Glycolysis
The 6-carbon sugar glucose is broken down in the cytosol into two 3-carbon pyruvic acid molecules with a net gain of 2 ATP and release of high-energy electrons.
High-energy electrons (e–) 1
Glycolysis 2 A T P
Cytosol
Pyruvic acid
Pyruvic acid
Citric Acid Cycle
The 3-carbon pyruvic acids generated by glycolysis enter the mitochondria. Each loses a carbon (generating CO2 and is combined with a coenzyme to form a 2-carbon acetyl coenzyme A (acetyl CoA). More high-energy electrons are released. 2
High-energy electrons (e–) CO 2
Acetyl Co A 3
Each acetyl CoA combines with a 4-carbon oxaloacetic
acid to form the 6-carbon citric acid, for which the cycle
is named. For each citric acid, a series of reactions
removes 2 carbons (generating 2 CO2’s), synthesizes
1 ATP, and releases more high-energy electrons.
The figure shows 2 ATP, resulting directly from 2
turns of the cycle per glucose molecule that enters
glycolysis.
Oxaloacetic acid
Citric acid
Citric acid
cycle
Mitochondrion
High-energy electrons (e–)
2 CO 2 2 A T P
Electron Transport Chain
The high-energy electrons still contain most of the
chemical energy of the original glucose molecule.
Special carrier molecules bring the high-energy electrons to a series of enzymes that convert much of the remaining energy to more ATP molecules. The other products are heat and water. The function of oxygen as the final electron acceptor in this last step is why the overall process is called aerobic respiration.
Electron
transport
chain 4
32–34 A T P 2e –
and 2H + O 2 H 2 O

16. Carbohydrate Storage Excess glucose stored as:
Glycogen (primarily by liver and muscle cells)
Fat
Converted to amino acids
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Carbohydrates
from foods
Hydrolysis
Monosaccharides
Catabolic
pathways
Anabolic
pathways
Energy + CO2 + H2O
Glycogen or Fat
Amino acids

17. Objectives (page 76) 4.1.1 Briefly explain the role of metabolism
4.2.1 Compare and contrast anabolism and catabolism
4.3.3 Describe how enzymes control metabolic reactions
4.4.5 Explain how cellular respiration releases chemical energy
4.4.6 Describe how energy in the form of ATP becomes available for cellular activities

18. Objectives (page 76) 4.6.8 Explain how DNA carries genetic info.
4.6.9 Define gene and genome
Describe how DNA molecules replicate

19. 4.6: Nucleic Acids and Protein Synthesis
Instruction of cells to synthesize proteins comes from a nucleic acid, DNA

20. Genetic Information
Genetic information – instructs cells how to construct proteins; stored in DNA
Gene – segment of DNA that codes for one protein
Genome – complete set of genes
Genetic Code – method used to translate a sequence of nucleotides of DNA into a sequence of amino acids

21. Structure of DNA Two polynucleotide chains – double-stranded
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Two polynucleotide chains – double-stranded
Hydrogen bonds hold nitrogenous bases together
Bases pair specifically (A-T and C-G)
Forms a helix
DNA wrapped about histones forms chromatin
chromosomes are condensed chromatin
(a) Hydrogen
bonds P G C P
Thymine (T)
Adenine (A) P T P
Cytosine (C)
Guanine (G) P C G P P G C P P A P G C
Nucleotide strand A G C T C G
Segment
of DNA
molecule A
(b)
Globular
histone
proteins
Chromatin
Metaphase
chromosome
(c)

22. DNA Replication Hydrogen bonds break between bases
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Hydrogen bonds break between bases
Double strands unwind and pull apart
New nucleotides pair with exposed bases
Controlled by DNA polymerase C G G C C G
Original DNA
molecule T A C G C G T A A T C G A T
Region of
replication G C C G G T A T A T A T T A A
Newly formed
DNA molecules G C G C T A T A C G C G C G C G T A A

23. DNA Replication DNA polymerase adds nucleotides one at a time
Nucleotides are always added in one direction only! 5’ to 3’
Leading strand – continuously synthesized
Lagging strand- synthesized in short fragments call Okazaki fragments
Fragments will later be joined together by DNA Ligase
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. A T C G G C C G
Original DNA
molecule T A C G C G T A A T C G A T
Region of
replication G C C G G T A T A T A T T A A
Newly formed
DNA molecules G C G C T A T A C G C G C G C G T A A 23

25. Objectives (page 76) 4.6.8 Explain how DNA carries genetic info.
4.6.9 Define gene and genome
Describe how DNA molecules replicate

26. Objectives (page 76) 4.7.11 Define genetic code
Describe the steps of protein synthesis

27. Genetic Code
Specification of the correct sequence of amino acids in a polypeptide chain
Each amino acid is represented by a triplet code

28. RNA Molecules
single-standed
ribose
uracil instead of thymine

29. RNA Molecules Messenger RNA (mRNA):
Making of mRNA (copying of DNA) is transcription
Transfer RNA (tRNA):
Carries amino acids to mRNA
Carries anticodon to mRNA
Translates a codon of mRNA into an amino acid
Ribosomal RNA (rRNA):
Provides structure and enzyme activity for ribosomes 29

30. RNA Molecules Messenger RNA (mRNA):
Delivers genetic information from nucleus to the cytoplasm
Single polynucleotide chain
Formed beside a strand of DNA
RNA nucleotides are complementary to DNA nucleotides (exception – no thymine in RNA; replaced with uracil)
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DNA
RNA S P A U P S S P T A P S S P
Direction of “reading” code G C P S S P C G P S S P G C P S

31. Protein Synthesis Cytoplasm 3 Translation begins as tRNA anticodons
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Cytoplasm 3
Translation begins as tRNA anticodons
recognize complementary mRNA codons,
thus bringing the correct amino acids into
position on the growing polypeptide chain
DNA
double
helix
Amino acids
attached to tRNA
Nucleus T A T A 6
tRNA molecules
can pick up another
molecule of the
same amino acid
and be reused G C G C 2
mRNA leaves
the nucleus
and attaches
to a ribosome A T A T
Polypeptide
chain
Messenger
RNA G C
DNA
strands
pulled
apart A T A T T U A C G G G C T A G G C G G C C C G 5
At the end of the mRNA,
the ribosome releases
the new protein C G T U A T A C C G G C C C G A T G C G C C G A A T G C A A T
Nuclear
pore 4
As the ribosome
moves along the
mRNA, more amino
acids are added
Amino acids
represented A T C C G C G G G C T A G G C 1
DNA
information
is copied, or
transcribed,
into mRNA
following
complementary
base pairing A C C G U
Codon 1
Methionine A A T G C G G G C T A G G C G G C C C G G
Codon 2
Glycine A T T U A C C C G C C G U G C A A T C
Codon 3
Serine A T T U A C C G G G C G T A A A T
Messenger
RNA
DNA
strand C
Codon 4
Alanine C C G G C A C G G C A T A C G C
Codon 5
Threonine G C A T G
Transcription
(in nucleus) G C
Translation
(in cytoplasm) G G C C
Codon 6
Alanine C G A U A G C G G
Codon 7
Glycine C

32. Protein Synthesis 1 2 1 The transfer RNA molecule
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The transfer RNA molecule
for the last amino acid added
holds the growing polypeptide
chain and is attached to its
complementary codon on mRNA.
Growing
polypeptide
chain 3 4
Next amino acid 5 6
Transfer
RNA
Anticodon U G C C G U A U G G G C U C C G C A A C G G C A G G C A A G C G U 1 2 3 4 5 6 7
Codons 1
Peptide bond 2 2
A second tRNA binds
complementarily to the
next codon, and in doing
so brings the next amino
acid into position on the ribosome.
A peptide bond forms, linking
the new amino acid to the
growing polypeptide chain.
Growing
polypeptide
chain 3 4
Next amino acid 5 6
Transfer
RNA
Anticodon U G C C G U A U G G G C U C C G C A A C G G C A G G C A A G C G U
Messenger
RNA 1 2 3 4 5 6 7
Codons 1 2
Next
amino acid 3
The tRNA molecule that
brought the last amino acid
to the ribosome is released
to the cytoplasm, and will be
used again. The ribosome
moves to a new position at
the next codon on mRNA. A 3 4 5 7 6
Transfer
RNA U G C C C G C G U A U G G G C U C C G C A A C G G C A G G C A A G C G U
Messenger
RNA 1 2 3 4 5 6 7
Ribosome 1 2 4
A new tRNA complementary to
the next codon on mRNA brings
the next amino acid to be added
to the growing polypeptide chain. 3 4 5
Next
amino acid 6 7
Transfer
RNA C G U C C G A U G G G C U C C G C A A C G G C A G G C A A G C G U
Messenger
RNA 1 2 3 4 5 6 7

33. Objectives (page 76) 4.7.11 Define genetic code
Describe the steps of protein synthesis