3.1 Cells are the smallest unit of life
interstitial fluid
- the fluid in tissues that bathes all of our cells - contains amino acids, sugars, fatty acids, regulatory substances and wastes - to remain healthy, each cell must extract from this mix the exact substances it needs depending on present conditions
fluid mosaic model
- the plasma membrane is a thin structure composed of a double layer (bilayer) of lipid molecules with protein molecules dispersed in it - the proteins form a constantly changing mosaic pattern
organelle
small structures that perform specific cell functions
body fluids (extracellular fluids)
- include interstitial fluid, blood plasma and cerebrospinal fluid - important transport and dissolving media
the extracellular matrix
- most abundant extracellular material - serve as universal "cell glue" - particularly abundant in connective tissues
extracellular materials
- substances contributing to body mass that are found outside the cells - includes body fluids, cellular secretions, extracellular matrix
cellular secretions
- substances that aid in digestion (intestinal and gastric fluids) - act as lubricants (saliva, mucus and serous fluids)
plasma membrane
- the cell's outer membrane - separates the intracellular fluid and the extracellular fluid - plays dynamic role in cellular activity
macrophages
cell that fights disease
nerve cell
cell that gathers information and controls body function
fat cell
cell that stores nutrients
fibroblasts, erythrocytes, epithelial cells
cells that connect body parts, from linings, or transport gases
skeletal muscle cell, smooth muscle cells
cells that move organs and body parts
Cell types
cells vary greatly in shape, size, function and length
the cell
the smallest unit of life
cell theory (4)
1) a cell is the basic structural and functional unit of living organisms 2) the activity of an organism depends on both the individual and the combined activities of its cells 3) according to the principle of complementarity of structure and function, the biochemical activities of cells are dictated by their shapes or forms, and by the relative number of the sub cellular structures they contain 4) cells can only arise from other cells
the generalized cell (composite cell) (3 parts)
1) plasma membrane: the outer boundary of the cell which acts as a selectively permeable barrier 2) cytoplasm: the intracellular fluid packed with organelles, small structures that perform specific cell functions 3) nucleus: an organelle that controls cellular activity (typically the nucleus lies near the cell's center)
