Biochemistry of Aging
Presented by Shanzay Annum Malik
• Gradual change in an organism that leads
to increased risk of weakness, disease,
and death over the entire adult life span of
any living thing.
• There is a decline in biological functions
and in ability to adapt to metabolic stress.
Changes in organs include
• reduced immunity,
• loss of muscle strength,
• decline in memory and cognition,
• loss of colour in the hair
• elasticity in the skin.
Gerontology and Geriatrics
• Gerontology is concerned with the
changes that occur between maturity and
death along with factors that influence
• Geriatrics focuses on health care of
elderly people and promote health by
preventing and treating diseases and
disabilities in older adults.
Factors of Aging
• mitochondrial damage
• free radicals
• apoptosis and necrosis
• other effects
Mitochondria: main unit of chemical power supply
• During the synthesis of macroergical bio-
molecules(high energy releasing
potentials e.g. ATP) free radicals are
being produced as the by-product.
• Free radicals released in large quantities
cause intercellular oxidative stress (e.g.
oxidative damage of mitochondria)
• damaging mitochondria and cause early
• A molecule that contains one or more
unpaired electrons &is capable of
• Eg : Superoxide H2O2,
• hydroperoxy radical (HOO+2
• lipid peroxideradical (ROO)
• Nitric oxide (NO)
Harmful effect of free radicals
• Because of their reactive nature, free radical can
provoke inflammation or altered cellular function
• Lipid peroxidation
• Protein modification
• DNA modification
Lipid peroxidation product:
• React with amino acid mainly CYS,
HIS,LYS to modify protein structure &
• Can crosslink lipid in cell membrane
interrupting structure & fluidity.
• Proteins are major targets of free radical attack because
of their high abundance & responsible for most of
• Free radical causes oxidation & modification of certain
amino acid (met, cys,His,try)
• ROS may damage protein by fragmentation
• net result is loss of biological activity of proteins
DNA modification :
• Free radical induced DNA damage
– strand break.
– DNA protein crosslink.
– large range of base & sugar modification.
• Repetitive DNA sequences at the ends of
all human chromosomes
• aging cells have shorter telomeres
• length differs between species
• in humans 8-14kb long
• Telomeres are thought to be the "clock"
that regulates how many times an
individual cell can divide.
• Telomeric sequences shorten each time
the DNA replicates.
• Once the telomere shrinks to a certain
level, the cell can no longer divide. Its
metabolism slows down, it ages, and dies
Apoptosis and Necrosis
• There are two ways that a cell can die:
• Necrosis occurs when a cell is damaged
by an external force, such as poison, a
bodily injury, an infection or getting cut off
from the blood supply (which might occur
during a heart attack or stroke). When
cells die from necrosis, it's a rather messy
affair. The death causes inflammation that
can cause further distress or injury within
• Apoptosis or programmed cell death
• When a cell is compelled to commit
suicide proteins called caspases go into
• They break down the cellular components
needed for survival,
• production of enzymes known as DNases,
which destroy the DNA in the nucleus of