BIOLOGY OF HUMAN AGING

CHAPTER 3

CELLULAR AGING

Cell components* Organelles* Nucleus* Cytoplasm* Plasma membrane

Plasma Membrane

• Phospholipids

• Associated proteins & lipids

• Intercellular space

Fluid Mosaic Model

Figure 3.3

Nucleus

• Nuclear membrane

• Contain genetic material

• Coded messages that direct synthesis of certain proteins

• DNA RNA Proteins

• DNA replication and transcription

From DNA to Protein

Figure 3.34

Cytoplasm

• mRNA is being translated to protein• rRNA and tRNA play a role in protein synthesis• There are other important organelles within the cytoplasm

– Endoplasmic rticulum– Ribosomes– Golgi Apparatus– Lysosomes– Mitochondria– Centrioles– Cytoskeleton

Structure of a Generalized Cell

Figure 3.2

Validity of cell-culture findings

• Programmed series of events– Growing cells in culture (in vitro vs. in vivo)Cells are similar and intrinsic control factors • Maintaining culture cells for a long time observe changes

resembled senescent body cells • Total # of divisions the cells undergo remains the same.• Limited capacity and regulation of the cell• Progeria

• Fibroblasts have shorter life span in culture media

Changes is nuclear DNA sequences occur with agingpossibility of failure of cellular mechanisms and repair enzymes

Specific Cellular Changes During Aging

• Membrane changes (problems in transporting materials permeability, Mitochondia, & Lysosome)

• Nuclear changes (problems in DNA synthesis, enzyme repair mechanism, condensing the DNA, manufacturing protein, and decrease in cell division

Cytoplasmic changes

• Dramatic increase in volume

• Decrease rate of DNA synthesis

• Gradual buildup of lipofuscin (age-pigment)

Ribosomal changes

• rRNA decreases with aging

• Decline in protein synthesis

• Decrease in the rate of elongation of the amino acid chains using ribosome

Mitochondrial changes

• Production of lipofuscin

• Apparent disorganization of the membrane

• Structural changes

• Decrease in number of mitochondria in postmitotic cells

• Decrease in energy and contribute to functional changes

Lysosomal changes

• Play an important role in intracellular digestion and breaking foreign substances

• With aging the action of the lysosomes is less efficient in older cells

• Accumulation of undigestible residues…• Changes in membrane• Changes in number• Changes in activity of enzymes