1. Cellular Metabolism-Chapter 4

2. 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

3. Metabolic Processes
Anabolism-synthesis reactions ex: dehydration synthesis (joining two molecules together by removing water)
Catabolism-breakdown reactions ex: hydrolysis (splitting of a molecule by the addition of water)

7. Control of reactions in metabolic pathways (series of reactions)
Enzyme-protein catalyst which controls the rate of a reaction by lowering the activation energy (energy needed to start the reaction)
Enzymes are needed in small amounts because they can be used over & over.
Enzymes are specific (each enzyme catalyzes ONE kind of reaction)

8. Each enzymes has an ACTIVE SITE which the substrate (reactant) fits into. The combination is called the ENZYME-SUBSTRATE COMPLEX.
The enzyme remains unchanged during the reaction.
Enzymes function at specific pH, temp, etc.
Enzyme helpers are: coenzymes (molecules such as vitamins) and cofactors (ions such as Ca++)

10. 4.3: Control of Metabolic Reactions
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
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Substrate molecules
Product molecule
Active site
Enzyme
molecule
Enzyme-substrate
complex
Unaltered
enzyme
molecule
(a)
(b)
(c)

12. 04_04 Enzyme catalyzed reaction
Slide number: 2
Substrate molecule
Active site
Enzyme molecule
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13. 04_04 Enzyme catalyzed reaction
Slide number: 3
Enzyme-substrate complex
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14. 04_04 Enzyme catalyzed reaction
Slide number: 4
Product molecules
Unaltered enzyme molecule
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15. Control of Metabolic Reactions
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
sucrase, lactase, protease, lipase

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

17. Animation: How Enzymes Work
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18. Energy release from breakdown of molecules
OXIDATION
Gradual enzyme-controlled breakdown in which much of the chemical energy is captured by energy carrying molecules and transferred to energy-requiring reactions in the cell. The rest is lost as heat.
BURNING
All of the chemical energy stored in the bonds of the molecule is released as heat and light.
Heat and light energy cannot be converted by a cell into other forms.

19. ATP-Adenosine Triphosphate-the cell’s energy carrier
ADP + P + energy
ATP can give up its energy.
ADP can pick up energy.

22. 4.5: Cellular Respiration
Occurs in a series of reactions:
Glycolysis
Citric acid cycle (aka TCA or Kreb’s Cycle)
Electron transport system

23. Cellular Respiration-process by which cells obtain energy from breakdown of foods - 3 stages
C6H12O6 + 6O2 ---> 6CO2 + 6H2O + energy
Hydrogen is gradually removed from glucose and carried by H-carriers (NADH and FADH) to the inner membrane of the mitochondrion where hydrogen combines with oxygen to form water.

24. Stages of cell respiration
Glycolysis-occurs in the cytoplasm-anaerobic-glucose is split into 2 molecules of pyruvic acid-a little ATP is made-some hydrogen is removed

26. If oxygen is present, the pyruvic acid now enters the mitochondrion to continue its breakdown: it changes to Acetyl CoA and enters:
Kreb’s (citric acid) cycle-occurs in the mitochondrion-aerobic-the rest of the H’s are removed-some ATP is made-CO2 is released

28. Electron Transport-occurs in mitochondrion-aerobic-NADH and FADH release H (H+ and e-) to the inner membrane--H+ passes through and e- flows down a set of proteins within the inner membrane, losing energy which is used to make lots of ATP--then the hydrogen ions combine with the electrons and oxygen to make water.

30. 4.5: Cellular Respiration
Occurs in a series of reactions:
Glycolysis
Citric acid cycle (aka TCA or Kreb’s Cycle)
Electron transport system

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

32. Glycolysis Series of ten reactions
Breaks down glucose into 2 pyruvic acid molecules
Occurs in cytosol
Anaerobic phase of cellular respiration
Yields two ATP molecules per glucose molecule
Summarized by three main phases or events:
Phosphorylation
Splitting
Production of NADH and ATP

33. Glycolysis Event 1 - Phosphorylation Two phosphates added to glucose
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Event 1 - Phosphorylation
Two phosphates added to glucose
Requires ATP
Phase 1
priming
Glucose
Carbon atom P
Phosphate 2
ATP
2 ADP
Fructose-1,6-diphosphate P P
Phase 2
cleavage
Event 2 – Splitting (cleavage)
6-carbon glucose split into two 3-carbon molecules
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

34. Glycolysis Event 3 – Production of NADH and ATP
Hydrogen atoms are released
Hydrogen atoms bind to NAD+ to produce NADH
NADH delivers hydrogen atoms to electron transport system if oxygen is available
ADP is phosphorylated to become ATP
Two molecules of pyruvic acid are produced
Two molecules of ATP are generated
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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

35. Anaerobic Reactions If oxygen is not available:
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If oxygen is not available:
Electron transport system cannot accept new electrons from NADH
Pyruvic acid is converted to lactic acid
Glycolysis is inhibited
ATP production is less than in aerobic reactions
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

36. 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
Carbon dioxide and water are formed
34 molecules of ATP are produced per each glucose molecule
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

37. Citric Acid Cycle
Begins when acetyl CoA combines with oxaloacetic acid to produce citric acid
Citric acid is changed into oxaloacetic acid through a series of reactions
Cycle repeats as long as pyruvic acid and oxygen are available
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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
(replenish molecule)
Oxaloacetic acid
Citric acid
(finish molecule)
(start molecule)
NADH + H +
CoA
NAD +
Malic acid
Isocitric acid
NAD +
For each citric acid molecule:
One ATP is produced
Eight hydrogen atoms are transferred to NAD+ and FAD
Two CO2 produced
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

38. Electron Transport System
NADH and FADH2 carry electrons to the ETS
ETS is a series of electron carriers located in cristae of mitochondria
Energy from electrons transferred to ATP synthase
ATP synthase catalyzes the phosphorylation of ADP to ATP
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

39. 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

40. Nucleic Acids and Protein Synthesis
A gene is a section of DNA which codes for the production of a polypeptide (chain of amino acids) in a cell. There are thousands of genes on a chromosome. Each chromosome is a DNA molecule.

41. 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

42. Deoxyribonucleic Acid (DNA) structure
made of 2 strands of nucleotides which spiral (double helix)
Each nucleotide contains: 5-C sugar (deoxyribose), phosphate, and a nitrogenous base (adenine, guanine, cytosine, or thymine)
The backbone of each strand is a sugar-phosphate chain
The bases of complementary strands hydrogen bond to each other: C-G, A-T

47. Animation: DNA Structure
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49. DNA Replication
H-bonds between base pairs break, separating the complementary strands
New nucleotides pair with each strand (C-G, A-T), resulting in two identical DNA molecules
Semiconservative

51. Ribonucleic Acid (RNA)-help DNA in protein production in cell
single strand of nucleotides
each nucleotide contains: ribose, phosphate, base (A, G, C, and Uracil instead of Thymine)
shorter than DNA
different types: mRNA (carries code from DNA to ribosome), tRNA (brings amino acids to ribosome), rRNA (a component of ribosomes)

52. Protein Production
1. Transcription-occurs in nucleus as DNA is converted into mRNA
2. Translation/protein synthesis-occurs on the ribosomes in the cytoplasm as amino acids join together

53. How can a gene provide a code for amino acid sequence in a polypeptide?
Each group of 3 bases on mRNA (codon) codes for 1 amino acid
The base sequence of a gene then determines the amino acid sequence in a polypeptide
But proteins are made in the cytoplasm, and DNA is in the nucleus---so mRNA helps by carrying the “code” from DNA to the ribosome

54. Transcription
a section of DNA opens up (just where the gene coding for the particular protein is)
mRNA nucleotides pair up with the DNA bases on one side (template)---uracil is used instead of thymine
formed mRNA moves away and DNA closes up
mRNA goes through nuclear pore and attaches to a ribosome in the cytoplasm

55. Animation: Stages of Transcription
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57. Translation
each tRNA molecule has an attachment point for a specific amino acid
each tRNA also has a region of 3 bases called an anticodon which is attracted to complementary mRNA codons
as the ribosome moves down the mRNA strand, tRNA’s bringing their aa’s are attracted to the mRNA codons

58. as tRNA goes to the mRNA (which is attached to a ribosome), it brings an amino acid with it--these aa’s then combine with each other and the tRNA’s leave
this results in a polypeptide chain and the ribosome “lets go”

59. Animation: How Translation Works
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61. animation

64. Animation: Protein Synthesis
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65. Mutation
A mutation is any change in the sequence of bases on DNA--could result in a change in the amino acid sequence of a protein

66. Nature of Mutations Mutations – change in genetic information
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Result when:
Extra bases are added or deleted
Bases are changed
Code for
glutamic
acid
Mutation
Code for
valine P P T T S S
Direction of “reading” code P P T A S S
May or may not change the protein P P C C S S
(a)
(b)