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Cell Doctrine:
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All living things are composed of cells
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A single cell is the smallest unit that exhibits all of the characteristics of life
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All cells come only from preexisting cells
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No living units smaller than a cell
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Cells make up all living things
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Single cell organisms to multicellular organisms
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All of our cells are derived for cells:
-fertilized egg (single cell)
-embryo (multicellular developing organs and tissues)
-new born (multicellular)
-to adult (grow more cells…)
-calls have specialized function
Cells are classified according to their internal organization:
Prokaryotic Cells
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Plasma membrane
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No nucleus
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Cytoplasm: fluid within membrane
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No true organelles
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Bacterial cells are prokaryotic
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Have ribosomes
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Smaller than eukaryotes
Eukaryotic Cells:
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Plasma membrane
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Nucleus: membrane bound information center
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Cytoplasm: fluid within membrane
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Organelles: membrane bound structures with specialized functions
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Have ribosomes
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All human cells are eukaryotic
Cell Structure Reflects Cell Function:
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Though eukaryotic cells are remarkably similar, these are structural differences
-Examples:
-muscle cells: contain numerous organelles providing energy needed for muscle
contraction
-nerve cells: long and thin to carry impulses and distance
* small size is efficient
Cells Remain Small to Stay Efficient:
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Small cells have a higher surface-to-volume ratio
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High surface-to-volume ratio promotes efficiency in
-acquisition of nutrients
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-disposal of wastes
* Larger a cell gets:
-harder to get waste out
-harder to get enough nutrients in
-cannot run metabolism
Visualizing Cells with Microscopes:
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Cells cannot be seen without magnification
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Microscopes enable visualization and study of cells
-Light Microscope
-magnifies up to 1000x
-can be used to view living specimens
-Transmission electron microscope
-magnifies up to 100,000x
-can reveal internal details of cell structure
-Scanning electron microscope
-magnifies up to 100,000x
-provides 3-D view of cell surface
Eukaryotes Have Organelles:
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Function
-membrane bound vesicles
-special function in cell
The Nucleus Controls the Cell
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Function
-contains the genetic information of the cell
-controls all of the activities of the cell
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Structural features
-double-layered nuclear membrane
-nuclear pores
-chromosomes/chromatin
-nucleolus
Ribosomes are Responsible for Protein Synthesis
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Site of protein synthesis
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Location
-Free: floating in cytoplasm
-these ribosomes synthesize proteins for immediate use
-Bound: attached to outer surface of endoplasmic reticulum
-these ribosomes synthesize proteins that will be transported to other organelles or
exported from the cell
