metabolism: fon 241; l. zienkewicz metabolism chapter 7

Metabolism: FON 241; L. Zienkewicz

Metabolism

Chapter 7


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.


• 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


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.


Metabolic Efficiency:

• Food energy is converted to ATP with approximately 50% efficiency.

• The other 50% is released as heat.

• When ATP is needed for energy, ~50% are used.

• Overall: 25% of food becomes energy

75% is released as heat.


The Cell:

Q: Approximately how many cells does

the human body contain?

A: 1x1014 cells or

100,000,000,000,000. (100 trillion cells)


The Cell:

• The site for metabolic activity.

• Liver cells are the most metabolically active.


How is energy produced?Three stages:

1. Proteins, Carbohydrates and Fats are broken down during digestion and absorption into smaller units: AA’s monosaccharides and fatty acids.

2. These smaller compounds are further broken down into 2-carbon compounds.

3. Compounds are degraded into CO2

and H20.


Helpers in reactions:

• Enzymes: proteins that facilitate chemical reactions without being changed in the process; protein catalysts.

• Coenzymes: assist enzymes in their activities.


Breakdown of nutrients for energy:

1. Glucose breakdown

2. Glycerol and Fatty Acid breakdown

3. Amino Acid breakdown

Common Pathway Energy

Fats

Carbohydrates

Protein


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


The path from Pyruvate to Acetyl CoA is NOT reversible.


2. Glycerol and Fatty Acid breakdown

Triglycerides are broken into:Glycerol and Fatty Acids (lipolysis).

Glucose

Glycerol

Pyruvate

Fatty acids

Acetyl CoA


3. Amino Acid breakdown

Glucose Amino Acids

Pyruvate Amino Acids

Acetyl CoA Amino Acids

TCA Cycle


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


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).


The Electron Transport Chain:

• The primary site for ATP (energy) synthesis.• Uses Oxygen to convert products of the TCA

cycle into energy.


Why is fat higher in energy?•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.


Weight Maintenance:

• Dietary fat can be easily transformed into body fat.

• Surplus protein leads to:1. Replacing daily losses.

2. Increased protein oxidation (energy).

3. Storage as fat.

• Surplus carbohydrate leads to:1. Storage as glycogen.

2. Increased CHO oxidation (variable w/ diet).

3. Storage as fat.


The body’s #1 priority:

1.Meet its energy needs.

metabolism: fon 241; l. zienkewicz metabolism chapter 7

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