METABOLISM
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Sum total of all chemical reactions in a living
organism
Chemical processes to provide energy, growth
substance and cell repair
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CATEGORIES
CATABOLISM
-
-
large biochemical
molecules
are
broken down ro
smaller ones
energy is released
ANABOLISM
-
-
small molecules
are joined to form
larger ones
requires energy
ADP and ATP – key components of metabolic
pathways
Net energy produced is used for cellular reactions
➢
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FLAVIN ADENINE DINUCLEOTIDE (FAD)
Coenzyme needed for numerous redox reactions
OXIDIZED FORM
Reduced form is FADH2
Oxidizing agent in conversion of alkane to an
alkene
➢
-
NICOTINAMIDE ADENINE DINUCLEOTIDE (NAD)
A coenzyme
Reduced form is NADH
3 subunit structure:
→ Nicotinamide-ribose-ADP
→ 6 subunit structure (nico-ribo-phosphos-ribo-adenine)
Serves as an oxidizing agent in the oxidation of
secondary alcohol to give ketone
METABOLIC PATHWAY (MP) – series of consecutive
biochemical reactions used to convert a starting material
into an end product
-
TYPES:
➢ Linear
➢ Cyclic
➢ COENZYME A
- Derivative of vitamin B
- Active in the form of sulfhydryl group (-SH
group) in the ethanethiol subunit
- Acetyl-CoA (acetylated)
IMPORTANT NUCLEOTIDE-CONTAINING
COMPOUNDS IN MP
➢ HIGH-ENERGY PHOSPHATE COMPOUNDS –
have greater free energy of hydrolysis than a
typical compound
- Contains strained bond (~) – they have at least
one reactive bond
- Less energy needed to break the bonds
- Free energy released is greater than 6.0
kcal/mole
➢ ADENOSINE PHOSPHATES (ATP, ADP, & AMP)
AMP – RNA’s structural component
-
Phosphate groups connected to AMP (thru
strained bonds) require less than normal energy
to hydrolyze them
CLASSIFICATION OF METABOLIC
INTERMEDIATE COMPOUNDS
BIOCHEMICAL ENERGY PRODUCTION
STEP 1: DIGESTION
→ Begins in the mouth, continues in the stomach,
completed in the small intestine
- Resulting small molecules can cross
intestinal membrane in to the blood
→ End products are absorbed in blood and
transported to body’s cells
- Glucose and monosaccharides
- Amino acids
- Fatty acids and glycerol
STEP 2: ACETYL GROUP FORMATION
→
Small molecules from stage 1 are further
oxidized
→
Reactions occur in cytosol (glucose metabolism)
and mitochondria (fatty acid metabolism)
→
Primary products: two-carbon acetyl units
(attached to coenzyme A = Acetyl CoA) and
NADH
→
End product is acetyl CoA
STEP 3: CITRIC ACID CYCLE
→
→
→
Takes place in mitochondria
→
Some are lost energy in the form of heat
Acetyl group is oxidized = CO2 and energy
Most energy is trapped and carried by NADH and
FADH2 to the fourth stage
STEP
4:
ETC
PHOSPHORYLATION
and
OXIDATIVE
→ Happens in mitochondria
→ NADH and FADH2 are oxidized and releases H+
that is transported to mitochondria’s
intermembrane space
→ Electrons transfer to O2 and will reduce to H2
→ H+ reenters the mito-matrix and drive ATPsynthase reaction to produce ATP – primary
energy carrier in metabolic pathways
Common Metabolic Pathways – sum of reactions that
occur in the citric acid cycle, ETC, and oxidative
phosphorylation.
CHEMICAL PROCESS PRIOR TO
METABOLISM
➢ Digestion – breakdown of food by hydrolysis
into simpler chemical units that can be used by
cells in metabolic processes
➢ Absorption – process where digested
molecules are transferred to bloodstream and
ultimately into the cells
- Takes place in small intestine thru villi (supplied
w/ network of blood vessels and a central lymph
vessel)