Metabolism refers to the chemical processes that maintain life, including energy metabolism. The body obtains energy from breaking down nutrients like glucose, fatty acids, and amino acids through a series of catabolic reactions. This releases energy in the form of ATP, which is then used to drive anabolic reactions that build complex molecules. Key processes in energy metabolism include glycolysis, the citric acid cycle, and the electron transport chain in the mitochondria, which use oxygen to convert nutrients into ATP with approximately 50% efficiency.

1. METABOLISM

2. Metabolism: FON 241; L. Zienkewicz
Metabolism:
• Metabolism: refers to the entire
network of chemical processes
involved in maintaining life.
• Energy metabolism: the ways that the
body obtains and spends energy from
food.

3. Metabolism: FON 241; L. Zienkewicz
• Anabolism: The building of compounds from
small molecules into larger ones. Energy is
used for this process to take place.
• Catabolism: The breakdown of molecules
into smaller units. Energy is released in this
process.
– Ex: Glucose catabolism results in the release of
CO2 and H2O

4. Metabolism: FON 241; L. Zienkewicz
ATP (Adenosine Triphosphate):
• The main energy source of cells.
• Used for muscular contractions,
enzyme activity, etc.
• Catabolism results in the production of
many ATP molecules: energy.
• Used by the body when energy is
needed.
• Hydrolysis breaks the bonds in ATP,
thus releasing energy.

5. Metabolism: FON 241; L. Zienkewicz
Metabolic Efficiency:
• Food energy is converted to ATP with
approximately 50% efficiency.
• The other 50% is released as heat.

6. Metabolism: FON 241; L. Zienkewicz
The Cell:
Q: Approximately how many cells does
the human body contain?
A: 1x1014
cells or
100,000,000,000,000. (100 trillion cells)

7. Metabolism: FON 241; L. Zienkewicz
The Cell:
• The site for metabolic activity.
• Liver cells are the most metabolically
active.

8. Metabolism: FON 241; L. Zienkewicz
How is energy produced?
Three stages:
1. Proteins, Carbohydrates and Fats are
broken down during digestion and
absorption into smaller units: AAs,
monosaccharides and fatty acids.
2. These smaller compounds are further
broken down into 2-carbon
compounds.
3. Compounds are degraded into CO2
and H20.

9. Metabolism: FON 241; L. Zienkewicz
Helpers in reactions:
• Enzymes: proteins that facilitate
chemical reactions without being
changed in the process; protein
catalysts.
• Coenzymes: assist enzymes in their
activities.

10. Metabolism: FON 241; L. Zienkewicz
Breakdown of nutrients for energy:
1. Glucose breakdown
2. Glycerol and Fatty Acid breakdown
3. Amino Acid breakdown
Common Pathway Energy
Fats
Carbohydrates
Protein

11. Metabolism: FON 241; L. Zienkewicz
1. Glucose breakdown
Glycolysis: A reaction in which glucose is
degraded to pyruvate; net profit: 2 ATP.
An anaerobic pathway.
Glucose
Pyruvate
Lactic Acid Acetyl CoA
Oxygen available
2 ATP
Less oxygen available

12. Metabolism: FON 241; L. Zienkewicz
The path from Pyruvate to Acetyl CoA is NOT reversible.

13. Metabolism: FON 241; L. Zienkewicz

14. Metabolism: FON 241; L. Zienkewicz
2. Glycerol and Fatty Acid breakdown
Triglycerides are broken into:
Glycerol and Fatty Acids (lipolysis).
Glucose
Glycerol
Pyruvate
Fatty acids
Acetyl CoA

15. Metabolism: FON 241; L. Zienkewicz
3. Amino Acid breakdown
Glucose
Amino Acids
Pyruvate
Amino Acids
Acetyl CoA
Amino Acids
TCA Cycle

16. Metabolism: FON 241; L. Zienkewicz
3. Amino Acid breakdown (cont.)
• Deamination: AA Keto acid and Ammonia
• Transamination
• Ammonia Urea in the Liver
• Urea excreted via the kidneys
• Water needed for urea excretion

17. Metabolism: FON 241; L. Zienkewicz
The TCA Cycle:
• Functions to convert Acetyl CoA to CO2
and to produce energy.
• Oxaloacetate combines with Acetyl
CoA to begin the cycle.
• The result: produces potential ATP
(energy).

18. Metabolism: FON 241; L. Zienkewicz
The Electron Transport Chain:
• The primary site for ATP (energy) synthesis.
• Uses Oxygen to convert products of the TCA
cycle into energy.

19. Metabolism: FON 241; L. Zienkewicz
Why is fat higher in energy?
•Fat’s carbon-hydrogen bonds can be easily oxidized, yieldin
energy (ATP).
•1 glucose molecule yields 38 ATP when oxidized.
•1 fatty-acid (16-C) will yield 129 ATP when oxidized.