3. 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.
4. Introduction to Metabolism
Enzymatic reactions do not work individually.
In cells- reactions rarely occur in isolation
Organized into a multi-step sequence
PATHWAYS:
Product of one reaction becomes a substrate of the next
reaction
Pathways intersect forming a network of reaction
METABOLISM: The sum of all chemical changes
5.
6. • 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 CO2and
H2O
Metabolism: FON 241; L. Zienkewicz
7. CATABOLIC PATHWAYS
Captures chemical
energy ATP from
degradation of energy-
rich molecules
Nutrients from diet are
converted into building
blocks for synthesis of
complex molecules
Energy generation steps:
•Hydrolysis of complex
molecules
•Conversion of building blocks
to Acetyl CoA
•Oxidation of Acetyl CoA
8. ANABOLIC PATHWAYS
Combines small
molecules to form
bigger molecules
Highly endergonic Uses ATP hydrolysis
Involves the use of
NADPH for reducing
power
Divergent process
Few biosynthetic
precursors form a
wide variety of
complex products
10. 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.
11. Metabolic Efficiency:
• Food energy is converted to ATP with
approximately 50% efficiency.
• The other 50% is released as heat.
12. The Cell:
Q: Approximately how many cells does
the human body contain?
A: 1x1014
cells or
100,000,000,000,000. (100 trillion cells)
13. The Cell:
• The site for metabolic activity.
• Liver cells are the most metabolically
active.
Metabolism: FON 241; L. Zienkewicz
14. 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 CO2and H20.
15. Helpers in reactions:
• Enzymes: proteins that facilitate chemical
reactions without being changed in the
process; protein catalysts.
• Coenzymes: assist enzymes in their activities.
16. Breakdown of nutrients for energy:
1. Glucose breakdown
2. Glycerol and Fatty Acid breakdown
3. Amino Acid breakdown
Common Pathway Energy
Fats
Carbohydrates
Protein
23. 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
Metabolism: FON 241; L. Zienkewicz
Oxygen available
2 ATP
Less oxygen available
24. 2. Glycerol and Fatty Acid breakdown
Triglycerides are broken into:
Glycerol and Fatty Acids (lipolysis).
Glucose
Glycerol
Pyruvate
Fatty acids
Acetyl CoA
25. 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).
Metabolism: FON 241; L. Zienkewicz
26. 3. Amino Acid breakdown
Glucose
Amino Acids
Pyruvate
Amino Acids
Acetyl CoA
Amino Acids
TCA Cycle
Metabolism: FON 241; L. Zienkewicz
27. 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
28. The Electron Transport Chain:
• The primary site for ATP (energy) synthesis.
• Uses Oxygen to convert products of the TCA cycle
into energy.
Metabolism: FON 241; L. Zienkewicz
29.
30. Why is fat higher in energy?
Metabolism: FON 241; L. Zienkewicz
• Fat’s carbon-hydrogen bonds can be easily
oxidized, yielding energy (ATP).
•1 glucose molecule yields 38 ATP when oxidized.
•1 fatty-acid (16-C) will yield 129 ATP when oxidized.
Notas del editor
When a bond is broken, as in the case of a glucose molecule being broken into CO2 and H2O during catabolism, energy is released in the process.
Some of this energy is trapped for cell use, and the rest is lost as heat.
Bonds within the ATP molecule, contain a high amount of energy.
When energy is needed in the body, these bonds are broken, which splits of a phosphate group.
Energy is released that can aid in anabolic reactions.
Page 211 in your text book.
Glucose is degraded into pyruvate with the end result being ATP.
A cell can take pyruvate and make glucose… a reversed process. But, this requires energy.
Degrading glucose into pyruvate requires a tiny amount of energy, but the energy it gains from the reaction is much larger.
Compounds that can be converted to pyruvate can be used to make glucose.
If the cell needs energy and oxygen is available, pyruvate is degraded into Acetyl CoA
If energy is not needed in the body, acetyl COA will be used to make fatty acids… increases the fat stores.
If less oxygen is available, the pyruvate is converted to lactic acid.This is an anaerobic reaction that occurs during high-intensity exercise.
This occurs when physical activity exceeds the rate at which the heart and lungs can deliver oxygen to and clear CO2 from the muscles.
This lactic acid can be converted by the liver to glucose in a recycling process called the Cori cycle.
Glycerol is easily converted to a 3-carbon compound that can be converted to pyruvate or can up up the chain to be converted to glucose.
Fatty acids cannot be converted to pyruvate.
But, they can be converted to acetyl CoA. These fatty acid fragments that are used to make pyruvate cannot be sent back up the chain to make glucose.
Thus, fatty acids cannot be used to make glucose.
Only 5% of the weight of a triglyceride is glycerol. The rest are fatty acids.
So, 95% of the triglyceride molecule cannot be converted into glucose.
Glycerol is NOT a viable source of glucose in the body.
Also called the Kreb’s cycle, the Citric Acid Cycle.
Oxaloacetate is crucial in facilitating the activity of the TCA cycle. It is a carbohydrate intermediate.
If Oxaloacetate is deficient, as may be the case in a low carb diet, cells face an energy shortage.
If amino acids are consumed in excess or if they are needed for energy, they enter a metabolic pathway.
They can be 1. Converted to glucose, 2. Converted to Acetyl CoA or 3. Be sent straight to the TCA cycle.
First, the AA’s must be deaminated, meaning they have their Nitrogen group.
If the AA are converted to acetyl Coa and energy is not needed, the Acetyl Coa is converted to fatty acids and stored.
Pages 218-219
Deamination: AA’s are broken down, first the nitrogen –containing amino group must be released.This leads to 1. Keto acid and 2. Ammonia
Transamination: The liver can use the keto-acids to synthesize nonessential amino acids.
In the deamination reactions, ammonia is produced. Remaining ammonia is combined with Co2 to make urea, a much less toxic compound than ammonia.
Urea is released into the blood and is removed from the blood by the kidneys for excretion in the urine.
The amount of protein ingested is related to the amount of urea that will need to be excreted.
If not enough water is consumed in extremely high protein diets, the urea cannot be excreted from the body and will accumulate in the blood.
Energy is captured within bonds of the ATP molecules.
Proteins serve as carriers within a cell, each carrier receives electrons (down a chain-like process).Little energy is released as heat, most of the energy is stored within the bonds of the ATP.
Text page 221.
Fat has many C-H bonds, making oxidation abundant.
Glucose molecules have some O already bound to the C bonds. Thus, not much is there for oxidation to take place.
Thus, much more energy can be released from fat, making it the ideal energy storage form.
