4. Cell Structure

4. Cell Structure - Cell structure Characteristics of life...

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Cell structure Characteristics of life 1) Complexity and organization in organism 2) Responds to environment (homeostasis) 4) Reproduction (heredity) 5) evolve Cell theory - first proposed in 1838 - all living things are made of cells - cells are smallest living things o basic unit of life - processes inherent to life occur within cells o metabolism, heredity - all cells come from pre-existing cells The size of cells - 1 um -> 1mm - In humans: largest = ovum; smallest = sperm
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Cell size limits - Transport substances in and out of cell o Limited by surface area o Need for energy determined by volume - Surface area to volume ratio o Decreases as size increases Cell types - Prokaryotic/eukaryotic - Vastly different architecture - Simple definition: o Prokaryotic: absence of a membrane-bound nucleus o Eukaryotic: presence of membrane-bound nucleus Prokaryotic cells - Lack nucleus & no internal membrane system - Divided into 2 domains o Bacteria o archaea - Tend to be small (1-10 um) - Dominant life form on the planet o Biomass domination o Huge diversity Prokaryotic cell structure - Circular DNA compacted into nucleoid - Cytoplasm: semifluid matrix that fills cell - Soluble cytosol & suspended particles - Organelles are also not membrane-bound - Ribosomes = universal organelle - Cell wall: made of carbohydrates - Plasma membrane (regulation)
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- Capsule: slimy outside protection - Pili: share genetic information; transport Eukaryotic cells - All cells have nucleus, membrane-bound that contains genetic material - Animal, plant, fungal cells, protists Compartmentalization - Organizing principle of eukaryotic cells: compartmentalization o Different compartments perform different functions o Usually membrane bound - Organelles: “little organs”, subcellular components with a specific function - Single organism may have many specialized cell types Cellular substructure - Structure and function of major organelles in animal and plant cells - Brief overview of cellular functions - We will see these organelles in action (what they do, what they’re composed of, etc) - Remember: the cell is the lowest level of organization that is ‘alive’ o What about viruses? (are not truly “alive” because they do not fulfill the five requirements of life as established above) Nucleus - Function: house genetic information o Storage of information o Expression of genetic information starts here (cell accesses information whenever it needs to – ex. transcribing/translation in protein synthesis) - Structure: o Nuclear envelope: double membrane (two bilayers) Has pores to control traffic with cytoplasm Inner membrane not the same as outer membrane
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Associates with different molecules but is closely associated with one another Outer connected to endomembrane system (inner is not) Features of the nucleus (check out figure 4.8) - Nucleolus o Specialized region (very dense) within nucleus (lots of activity going on
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This note was uploaded on 10/24/2011 for the course BIOL 110 taught by Professor Mason during the Fall '07 term at Purdue.

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4. Cell Structure - Cell structure Characteristics of life...

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