biology of human aging chapter 3 cellular aging. cell components * organelles * nucleus * cytoplasm...
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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
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