1. Chapter 5 Cell Respiration & Metabolism
Remon Wahba, MD

2. Chapter 5 Outline Glycolysis Lactic Acid Pathway Aerobic Respiration
Fat & Protein Metabolism
5-2

3. Metabolism
All reactions in the body that involve Energy Transformations
5-3

4. Metabolism Catabolism Anabolism Divided into 2 categories:
Breaking down of molecules to Release Energy
Is primary source of energy for making ATP
Anabolism
Formation (synthesis) of larger molecules
Requires Energy
Source of body’s large energy-storage compounds

5. Metabolism continued
5-4

6. Glycolysis
5-4

7. Glycolysis Breaking down of Glucose Molecules
Does not require Oxygen (Anaerobic)
Occurs in the Cytoplasm
Glucose Molecules split into 2 Molecules of Pyruvate
Small amount of Energy is liberated
2 ATP ( Adenosine Tri Phosphate)
2 NADH ( Nicotinamide Adenine Di Nucleotide

8. Glycolysis (cont) Glycolysis is Exergonic
Produces net of 2ATPs & 2NADHs
However, glucose must be activated with 2ATPs (phosphorylation) before energy can be obtained
Phosphorylation traps glucose inside cell
So 2 ATPs are used & 4 ATPs are produced (net gain of 2 ATP)
5-6

9. Glycolysis (cont)
Fig 5.2
5-7

10. Lactic Acid Pathway
For Glycolysis to continue, NADHs produced need to give its Hs away
In absence of O2,
NADH gives its Hs to pyruvate creating Lactic acid (Anaerobic Respiration)
In the presence of O2,
NADH gives its Hs to O2 forming Water (Aerobic Respiration)
5-8

11. Lactic Acid Pathway

12. Lactic Acid Pathway continued
Also called Lactic Acid Fermentation
Occurs in Skeletal & Heart muscles when oxygen supply falls below critical level
During Heavy Exercise or Vascular Blockage
Occurs in RBCs
Don't have mitochondria
Use only lactic acid pathway
5-9

13. Glycogenesis & Glycogenolysis
For osmotic reasons cells can't store many free Glucose molecules
Glycogenesis
Storage of Glucose as Glycogen
Skeletal Muscles & Liver store lots of Glycogen
Glycogenolysis
Breaking down of Glycogen to release Glucose as glucose 6-phosphate
Phosphate groups trap Glucose molecules inside cells
5-10

14. Glycogenesis & Glycogenolysis continued
Skeletal muscles use trapped glucose-6-phosphate for their own energy needs
Liver has glucose-6-phosphatase that removes phosphate groups
So glucose can be released into the blood stream to be used by All Body Cells
5-11

15. Cori Cycle Some Lactic Acid produced in skeletal muscle goes to Liver
Where it is converted back into Pyruvate then to Glucose & Glycogen
This process is called: Gluconeogenesis
(Formation of new glucose)
5-12

16. Cori Cycle
Helps to:
Restore Skeletal Muscle Glycogen which was consumed during exercise
Remove Lactic Acid from the Blood

17. Cori Cycle

18. Aerobic Respiration
5-13

19. Aerobic Respiration Occurs in the Mitochondria
Requires the presence of Oxygen (aerobic)
Pyruvates are broken down and CO2 is produced
Large amount of Energy is Produced (34-36 ATP)

20. Aerobic Respiration
Begins when Pyruvate formed by Glycolysis enters Mitochondria
C02 is removed from Pyruvate forming Acetyl CoA (Coenzyme A is a carrier for acetic acid)
C02 goes to lungs to be excreted
Energy in Acetyl CoA is extracted during Aerobic respiration in mitochondria
5-14

21. Aerobic Respiration

22. Krebs Cycle
Begins with Acetyl CoA combins with Oxaloacetic Acid to form Citric Acid
In a series of reactions Citric Acid is converted back to Oxaloacetic Acid to complete the pathway
Two ATP molecules are produced in the Krebs Cycle from every glucose molecule
Large amount of ATP is produced by Electron Transport Chain (ETC) from NADH and FADH

23. Electron Transport Chain
Chain of molecules in inner mitochondrial membrane
Molecules undergo Oxidation / Reduction reactions and Energy is released.
Energy released is used to synthesize ATP by Oxidative Phosphorylation
O2 is the Last electron acceptor
and water is formed

24. Krebs Cycle

25. Krebs Cycle continued
Fig 5.8
5-17

26. Function of Oxygen
Allows Electron Transport to continue by acting as The Final Electron Acceptor
O2 accepts these electrons & combines with 4H+s to form 2 water molecules
O2 + 4 e- + 4 H+  2 H20
In the absence of O2, the Kreb’s cycle would stop and Respiration becomes Anaerobic

27. ATP Formation ATP can be made by 2 ways:
Direct (substrate-level) phosphorylation
Where ATP is generated when bonds break
2 ATPs in Glycolysis are made this way
2 ATPs / glucose in Kreb's made this way
Oxidative Phosphorylation
Where ATP is generated by ETC (Electron Transport Chain)
ATPs are produced this way (some are used to pump ATP out of the Mitochondria)
5-23

28. Net Production of ATP
2 from Glycolysis
2 from Direct Phosphorylation in Krebs Cycle
26 from Oxidative Phosphorylation in ETC
A total of 30 ATPs are produced from each Glucose Molecule

29. Fat & Protein Metabolism
5-28

30. Fats & Proteins as Energy Sources
Fats are hydrolyzed to Glycerol & Fatty acids
These can be modified to run through Kreb's
Proteins are broken down to Amino Acids
Which can be Deaminated & run through Kreb's
These pathways can be used to interconvert Carbohydrates, Fats, & Proteins
5-29

31. Fats
Glycogen
Protein
Glucose
Amino acids
Carbon
backbone
NH3
Urea (waste)
Fatty acids
Glycerol
Pyruvate
Citric
acid
cycle
Acetyl
CoA
Electron
transport
system
Preparatory
step
(2)
many
Figure 3.30

32. Energy Storage
When more energy is taken in than consumed, ATP synthesis is inhibited
Glucose is converted into:
Glycogen
&
Fat
5-30

33. Acetyl CoA Is a common Substrate for energy & synthetic pathways
Fig 5.12
5-31

34. Fat Synthesis (Lipogenesis)
Acetyl CoAs
Can be linked together to form fatty acids
Fatty acids + glycerol = Fat (Triglycerides)
Occurs mainly in:
Adipose Tissue
&
Liver
5-32

35. Fat Synthesis (Lipogenesis)
Fat is a major form of energy storage in body
Yields 9 kilocalories/gram
Carbs & proteins yield only 4 Kilocalories/g
Most Energy stored in the body is in the form of Triglycerides

36. Lipolysis Is breakdown of fat into Fatty Acids & Glycerol
Via hydrolysis by Lipase
Acetyl CoAs from free fatty acids serve as major energy source for many tissues
5-33

37. Ketone Bodies
Triglycerides are continually broken down & resynthesized
Ensures blood will contain fatty acids for Aerobic Respiration
During Fasting, Severe Dieting & in Severe Diabetes large amount of fat is broken down
Causes high levels of Free Fatty Acids
Some are converted by the Liver into ketone bodies
Give breath an Acetone smell
5-36

38. Amino Acid Metabolism Nitrogen (N) ingested primarily as Protein
Which is used in body as Amino Acids
Excess is excreted mainly as Urea
5-37

39. Nitrogen (N) Balance Nitrogen balance = N ingested Vs. N excreted
Positive N balance:
N ingested is more than excreted
Negative N balance:
N ingested is less than excreted
In Healthy Adults:
Amount of N excreted = Amount ingested
5-38

40. Nitrogen (N) Balance Carbs (Gluconeogenesis) Fat (Lipogenesis)
Excess amino acids are not stored in the body
Can be converted into:
Carbs (Gluconeogenesis)
Fat (Lipogenesis)

41. Essential & Non-essential Amino Acids
20 amino acids used to build proteins:
12 can be produced by body (Non-essential)
8 must come from diet (Essential Amino Acids)
Proteins of Animal Origin are rich in Essential Amino Acids
5-39

42. Essential & Non-essential Amino Acids

43. Transamination
Transfer of Amine Group from one Amino Acid to create another one
New Amino Acids can be produced
Addition of -NH2 group to pyruvate or Kreb's cycle Acids (Keto Acids) to make a new amino acid
Catalyzed by Transaminase
5-40

44. Oxidative Deamination
Is process by which excess Amino Acids are eliminated
-NH2 (Amine group) is removed from Glutamic acid, forming keto acid & Ammonia
Ammonia is converted to urea & excreted
Keto acid goes to Kreb’s or to Fat or Glucose
5-42

45. Gluconeogenesis
The formation of new Glucose from Non- Carbohydrate molecules.
During Prolonged Fasting most of Blood Glucose is produced in the Liver by Gluconeogenesis

46. Gluconeogenesis New glucose can be formed from: Amino Acids
Amino Acids are converted to Keto Acids, then Pyruvate, then Glucose
Glycerol
From the breakdown of Lipids
Lactate
Lactates are first converted into Pyruvates then to Glucose (Cori Cycle)

47. Uses of Different Energy Sources
Different cells have different preferred energy substrates
Brain uses glucose as its major source of Energy
5-44

48. Uses of Different Energy Sources

49. Terms to Remember Glycolysis Glycogenesis Glycogenolysis
Breakdown of Glucose into 2 Pyrovate
Glycogenesis
Formation of Glycogen from Glucose
Glycogenolysis
Breaking down of Glycogen to release Glucose
Gluconeogenesis
Formation of Glucose from Noncarbohydrate

50. Terms to Remember Lipolysis Lipogenesis Ketogenesis:
Breakdown of Lipids into Fatty Acids & Glycerol
Lipogenesis
Formation of Lipids for storage
Ketogenesis:
Formation of Ketone Bodies from Fatty Acids
Occurs in the Liver