biochem metabolism i

BIOENERGETICSHOW THE BODY CONVERTS FOOD TO ENERGY

Geromil J. Lara, RMT, MSMT

METABOLISM• Is the sum total of all the chemical

reactions involved in maintaining the dynamic state of the cell– Metabolic Reactions

• Those in which molecules are broken down to provide the energy needed by cells – catabolism

• Those that synthesize the compounds needed by cells – anabolism

METABOLISM• Biochemical Pathway

– Is a series of consecutive biochemical reactions• Carbohydrates• Lipids• Proteins

• Common Catabolic Pathway– To convert the chemical energy in food

to molecules of ATP

METABOLISM• Principal Compounds of the

Common Catabolic Pathway– Common Catabolic Pathway

• Citric Acid Cycle

• Oxidative Phosphorylation Pathway– Electron Transport Chain– Phosphorylation


Common Catabolic Pathway– Agents for Storage of Energy and

Transfer of Phosphate Groups

• Adenosine Monophosphate (AMP)• Adenosine Diphosphate (ADP)• Adenosine Triphosphate (ATP)


Common Catabolic Pathway– Agents for Transfer of Electrons in

Biological Oxidation-Reduction Reactions• Coenzymes

– NAD+ (nicotinamide adenine dinucleotide)

– FAD (flavin adenine dinucleotide)» Contain and ADP core


Common Catabolic Pathway– Agent for Transfer of Acetyl Groups

• Coenzyme A– Final principal compound – Acetyl (CCH3CO–)-transporting

molecule– Contains ADP

CATABOLISM• Stage I: Hydrolysis of Dietary

Macromolecules into Small Subunits

– To degrade large food molecules into their component subunits• Simple sugars, amino acids, fatty acids,

and glycerol

• Digestive processes

CATABOLISM• Stage II: Conversion of Monomers

into a Form that can be Completely Oxidized– Monosaccharides, amino acids, and

glycerol are assimilated into the pathways of energy metabolism

• Glycolysis• Citric Acid Cycle (Tricarboxylic Acid Cycle

or Kreb’s Cycle)


into a Form that can be Completely Oxidized– Sugars – usually enter the glycolysis

pathway in the form of glucose or fructose

– Eventually converted to acetyl-CoA, which can be completely oxidized in the citric acid cycle


into a Form that can be Completely Oxidized– Amino groups – are removed from

amino acids– Remaining carbon skeletons enter the

catabolic processes at many steps of the citric acid cycle


into a Form that can be Completely Oxidized

– Fatty acids – are converted to acetyl-CoA and enter the citric acid cycle in that form


into a Form that can be Completely Oxidized– Glycerol – produced by the hydrolysis

of fats– Converted to glyceraldehyde-3-

phosphate (one of the intermediates of glycolysis)

– Enters energy metabolism

CATABOLISM• Stage III: The Complete Oxidation of

Nutrients and the Production of ATP– Acetyl CoA – carries 2-carbon remnants

of the nutrients, acetyl groups, to the citric acid cycle

– Electrons and hydrogen atoms are harvested during the complete oxidation of the acetyl group to CO2• Used in the process of oxidative

phosphorylation to produce ATP

(1) GLYCOLYSIS• Also known as the Embden-Meyerhof

Pathway• A pathway for carbohydrate catabolism

that begins with the substrate D-glucose– Anaerobic process– 10 steps

– 3 Major Products• ATP – chemical energy• NADH – chemical energy• 2 three-carbon pyruvate

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ENZYME MNEMONICS

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PENTOSE PHOSPHATE PATHWAY

• An alternative pathway for glucose oxidation

• It provides the cell with energy in the form of reducing power for biosynthesis– NADPH is produced in the oxidative stage

• Reducing agent required for many biosynthetic pathways

• Provides sugar phosphates that are required for biosynthesis

• Most active in tissues involved in cholesterol and fatty acid biosynthesis

biochem metabolism i

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