JUMALON, JOHN DEXTER A.
Metabolism – sum total of all the
chemical reactions involved in
maintaining the dynamic state of the cell
Metabolic Reactions:
Catabolism – molecules are broken down
to provide the energy need by cells.
Anabolism – synthesize the compounds
needed by cells
Biochemical Pathway
- series of consecutive biochemical
reactions
• Carbohydrates
• Lipids
• Proteins
Common Catabolic Pathway
- convert the chemical energy in food
molecules of ATP
Acetyl – CoA Citric acid
cycle Oxidative phosphorylation
ETC (Electron Transport Chain)
Principal Compounds of the Common
Catabolic Pathway
Agents for Storage of Energy and
Transfer of Phosphate Groups
• Adenosine Monophosphate (AMP)
• Adenosine Diphosphate (ADP)
• Adenosine Triphosphate (ATP)
ATP
- contains 5-carbon sugar, three
phosphate groups and an adenine base
- energy is released when the bond
between the 2nd phosphate group and the
3rd phosphate group is broken
Agents for Transfer of Electrons in
Biological Oxidation-Reduction
Reactions
• Coenzymes
●NAD+ - nicotinamide
adenine dinucleotide (oxidized
form)
●FAD+ - flavin adenine
dinucleotide (oxidized form)
●NADH – nicotinamide
adenine dinucleotide (reduced
form)
●FADH – flavin adenine
dinucleotide (reduced form)
Agents for Transfer of Acetyl Group
• Coenzyme A
• Final principal compound
• Acetyl (CH3CO-) – transporting
molecule
Acetyl group – B-mercaptoethylamine
Pantothenic acid – 3’ – 5’ - 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 process
(DI NAKO MAHANAP SA GOOGLE ANG
PIC DIRI)
Stage II: Conversion of Monomers 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
Amino Groups
- are removed from amino acids
- remaining carbon skeletons enter the
catabolic processes at many steps of the
citric acid cycle
Fatty Acids
- are converted to acetyl-CoA and enter
the citric acid cycle in that form
Glycerol
- produced by the hydrolysis of fats
- converted to
glyceraldehyde-3-phosphate (one of the
intermediate of glycolysis)
- enters energy metabolism
Monosaccharides, amino acids, and
glycerol are assimilated into the
pathways of energy metabolism
• Glycolysis
• Citric Acid Cycle (Tricarboxylic Acid Cycle
or Kreb’s Cycle)
Stage III: Complete Oxidation of
Nutrients and 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 acetyl group to CO2
- used in the process of oxidative
phosphorylation to produce ATP
GLYCOLYSIS
- known as Embden-Meyerhof Pathway
- a pathway for carbohydrates 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
Key points:
• occurs in cytosol
• starts with glucose; ends with 2
pyruvates
• works in aerobic or anaerobic condition
• 2 ATP consumed/glucose
• 4 ATP produced/glucose
• 2 NADH & H+produced/glucose
