Cell~2008(notes with px)

Cell~2008(notes with px) - The Cell Refer to reference text...

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The Cell - Refer to reference text chapter from Basic Histology , Ninth edition, Junqueira. Chapters 2 and 3. A. Definition- The cell is the structural unit of all living organisms - has available to it the genetic material which allows it to carry out independently all of the vital functions to sustain life. Cell specialization or differentiations are cell modifications to increase physiological efficiency. (ex: muscle cell. Cell shape, organization among other cell and cell products) B. Cellular functions: 3 activities are basic to living organisms: nourishment, growth / development, and reproduction. C. Cell Constituents 1. Protoplasm denotes the entire living substance of the cell. Includes the cytoplasm (substance of the cell outside the nucleus) and the karyoplasm (the substance of the nucleus). 2. Cytoplasmic matrix = studies indicate that the cytoplasm is an organized structure within an aqueous gel. Eukaryotic cells have a distinct nucleus with nuclear envelope and membranous organelles 1
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3. Membrane-limited structures of the cell; cellular microcompatments in in which products are segregated: plasma membrane, RER, SER, Golgi apparatus, mitochondria, lysosomes, endosomes, peroxisomes, nucleus 4. Non-membranous structures of the cell: microtubules, filaments, centrioles, ribosomes, inclusions (lipid, glycogen – non membranous; pigment – membranous) D. Plasma Membrane – forms the cell boundary; forms the boundaries of many cell organelles. Ion and nutrient transport; recognition of environmental signals; cell-to- cell extracellular matrix adhesions 1. Molecular composition: a limiting membrane composed of lipids, protein, and oligosaccharides linked to lipids or protein. Has specific recognition and regulatory functions. a. Lipids (1) Phospholipids are arranged in a double layer with their hydrophobic (non-polar) chains directed toward the center of the membrane and the hydrophilic (polar) heads directed outward. The lipids of either layer can differ. (2) Cholesterol: mechanically stabilizes the cell membrane. Regions of high in concentrations of cholesterol and glycosphingolipids (longer, highly- saturated f.a. chains; create ‘lipid rafts’. Lipid rafts exhibit less fluidity than the surrounding plasma membrane. Involved in cell signaling and separating different parts of the cell membrane. 2
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(3) Glycolipids: CHO attached to lipids of the outer face of the bilayer; establish extracellular microenvironments at the membrane surface that have specific functions in metabolism, cell recognition, and cell associations; serve as receptor sites for hormones i. Glycocalyx or cell coat: surface molecules of glyolipids and glycoproteins b. Proteins: Most membrane proteins are globular; they are divided into two groups - integral and peripheral. They constitute half of the mass of the cell membrane. Integral proteins are directly incorporated within the lipid bilayer; peripheral proteins have a looser association with the inner or outer portion of the membrane and
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Cell~2008(notes with px) - The Cell Refer to reference text...

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