1. Metabolism of Nutrients
Eko Widodo

2. Metabolism Metabolism Energy Metabolism
The sum total of all the chemical reactions that go on in living cells
Energy Metabolism
Includes all the reactions by which the body obtains & spends energy from food
All energy sustaining life initially comes from the sun

3. The Site of Metabolic Reactions
Metabolic reactions take place inside cells, especially liver cells
Anabolism is the building up of body compounds and requires energy.
Catabolism is the breakdown of body compounds and releases energy.
Type & extent of metabolic activity vary depending on type of cell.

4. The Site of Metabolic Reactions
Cytosol (jelly like fluid of cytoplasm) – enzymes involved in glycolisis
Ribosomes – assemble proteins
Mitochondria – powerhouses of cells
Pyruvate to acetyl coA
Fatty acid oxidation
TCA cycle and electron transport chain

5. Energy Yielding Nutrients
From CHO → glucose
From fats → glycerol & FA
From proteins → AA
4 basic units used in metabolic pathway
Alcohol can disrupt normal metabolic pathways (Highlight 7)

7. The Transfer of Energy in Reactions - ATP
ATP – adenosine triphosphate
High-energy storage compound
Captures some energy released during breakdown of glucose, glycerol, fatty acids, and amino acids
Think of ATP as our energy currency

8. Adenosine Triphosphate (ATP)
Red squigly lines denote high energy bonds between the 3 phosphates

9. The Transfer of Energy in Reactions - ATP
Hydrolysis of ATP occurs simultaneously with reactions that will use that energy
Coupled reactions
Energy released from breakdown of one compound used to create bond in formation of another
Think of ATP as our energy currency

11. Enzymes & Co-enzymes – Helpers in Metabolism
Co-enzymes are organic molecules that work with enzymes to facilitate their activity.
Enzymes & co-enzymes are helpers in metabolic reactions.
Some B vit serve as coenzymes to enzymes that release energy from glucose, glycerol, FA & AA.

12. Breaking Down Nutrients for Energy
Basic units enter metabolic pathways. During catabolism, the body separates atoms of basic units.
Glucose: 6 C
Glycerol: 3 C
FA: even number of C (commonly 16 or 18)
AA: 2, 3 or more C, with N attached
While each starts down a different path – 2 by- products are common
pyruvate & acetyl-coA
Eventually all enter the TCA cycle & electron transport chain
Pyruvate – 3 carbon structure
Acetyl-coA – 2 carbon structure with coA attached

13. Glycolysis Glucose Glucose splitting
6-C Glucose → two 3-C compounds → Pyruvate
Glucose
anaerobic
Pyruvate

14. Show animation!

15. Pyruvate to Acetyl CoA Pyruvate Pyruvate Lactate Acetyl CoA
If cell needs energy (& O2 is available), it removes COOH group from pyruvate to produce 2 C compounds that bonds with CoA to form Acetyl CoA
Pyruvate
Acetyl CoA
Absence of sufficient O2 (or mitochondria) pyruvate is converted to lactic acid
Pyruvate
anaerobic
Lactate
Lactate recycled to glucose in liver by Cori cycle
aerobic

17. Paths of Pyruvate & Acetyl CoA
Point out that once turned into acetyl coA cannot go back to pyruvate (can go back to fatty acids)

18. Glycerol to Pyruvate Glucose Glycerol Pyruvate
3-C glycerol is easily converted to pyruvate
Also easily converted to glucose
Glucose
Glycerol
Pyruvate

19. Fatty Acids to Acetyl CoA
FA are taken apart in 2-C units through fatty acid oxidation.
2-C units split off & combine with CoA to form Acetyl CoA.
If cell doesn’t need energy, acetyl CoA molecules combine to create TG.

20. Show animation!

21. Amino Acids Breakdown Deaminated first (lose N)
Catabolized in a variety of ways:
Pyruvate  glucose
Acetyl CoA  more energy or body fat
Directly into TCA Cycle  generate energy

23. Amino Acids Breakdown Amino Acids Deamination results in two products:
Keto acid
Ammonia
Transamination is the transfer of the amino group from an amino acid to a keto acid.
Ammonia is converted to urea—a much less toxic compound—in the liver.
Urea is excreted through the kidneys to rid the body of unused nitrogen.

27. Breaking Down Nutrients for Energy
In Summary
Glucose and fatty acids are primarily used for energy, amino acids to a lesser extent.
Glucose is made from all carbohydrates, most amino acids and the glycerol portion of fat.
Protein is made from amino acids.
Glucose can be made into nonessential amino acids if nitrogen is present.
All energy-yielding nutrients consumed in excess can contribute to fat storage.

28. Breaking Down Nutrients for Energy – the final steps
TCA Cycle – tricarboxylic acid cycle (aka
Kreb’s cycle)
Oxaloacetate picks up acetyl CoA & drops off 2-C & returns to pick up another acetyl CoA.
As acetyl CoA breaks to CO2, H atoms with their electrons are removed.
Coenzymes made from B vitamins take H & electrons & transfers them to ETC.
Show animation

30. Breaking Down Nutrients for Energy – the final steps
Electron Transport Chain (ETC)
Consist of a series of proteins that serve as electron carriers. These carriers are inside inner membrane of mitochondria.
In ETC, energy is captured in bonds of ATP molecules.
ATP leaves mitochondria & enters cytoplasm, where it can be used for energy.
Show animation

32. Kcal/gram
Each ATP holds energy & Kcal measures energy, so the more ATP generated the more Kcal collected.
One glucose molecule yield ATP when oxidized completely.
One 16 carbon FA yield 129 ATP when oxidized completely.

34. Energy Balance - Surplus
When energy intake exceeds energy output, there is a gain in weight.
Fat cells enlarge & multiply regardless of whether the excess comes from protein, CHO or fat.
Most direct & efficient pathway to body fat is dietary fat.

35. Energy Balance Body needs energy all the time
Relies on energy stores between meals
glycogen
fatty acids
lean mass tissue .. least preferred

36. Energy Balance – Fasting/Starvation
Fasting—Inadequate Energy
Glucose needed for the brain
Protein meets glucose needs
The shift to ketosis
Ketones are produces when glucose is not available.
Ketosis causes a suppression of the appetite.
Slowing of metabolism

37. Energy Balance – Fasting/Starvation
Fasting—Inadequate Energy
Symptoms of starvation
Muscle wasting
Decreased heart rate, respiratory rate, metabolic rate, and body temperature
Impaired vision
Organ failure
Decreased immunity
Depression, anxiety, and food-related dreams

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