BIOL&251Ch3NotesSpr11

BIOL&251Ch3Notes - Living organisms are made of one or more cells A cell is the smallest unit of life(that performs all vital physiological

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1 • Cell diversity: there are over 200 specific types of cells in the body – There are 2 general cell types: gametes (= sperm and oocytes; a.k.a. sex cells, germ cells, or reproductive cells) and somatic cells (= all other cells) Ch. 3 – Cells • Living organisms are made of one or more cells • A cell is the smallest unit of life (that per- forms all vital physiological functions) • Cells arise from the division of preexisting cells • Each cell maintains homeostasis at the cellular level Organismal homeostasis reflects the combined, coordinated actions of many cells A generic “model” cell (Table 3-1 summarizes all the parts) Cells have a large surface area (supply) to volume (demand) ratio Cells are surrounded by a watery extra cellular (or interstitial) fluid (ECF) •T h e cell (plasma) membrane separates the outside environment (ECF) from the inside of the cell (cytoplasm) Cytoplasm = the cell contents, consisting of: Cytosol = a watery fluid Organelles = intracellular “little organs” that carry out specific vital cell tasks
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2 The cell (plasma) membrane • Main functions : Barrier : it physically isolates the inside of the cell (cytoplasm) from its external environment (ECF) –It regulates exchange with the environment –It recognizes and responds to the environment Binding : it provides structural support to tissues • Structure (see the next slide) : – It’s a phospholipid bilayer , with proteins, other lipids, and carbohydrates too Fig. 3-2, p. 70 Cell membrane structure
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3 Membrane lipids • The vast majority are phospholipids – These have hydrophilic heads and hydrophobic tails • There is also some cholesterol – This helps maintain the consistency of membrane fluidity Membrane proteins • Can be classified by their position in the membrane : Integral (transmembrane) proteins : span the entire thickness of the membrane Peripheral proteins :a re attached to the inner or outer surface of the membrane • Can also be classified by their function (see the next
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4 Membrane proteins (As classified by their function) Anchoring proteins : attach cells to other cells or structures Recognition proteins ( identifiers ; e.g. MHC): serve as identification for the body’s cells by the immune system Membrane proteins (As classified by their function) Enzymes : catalyze reactions Receptor proteins : bind to specific ligands (extracellular signal molecules)
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5 Membrane proteins (As classified by their function) Carrier proteins (transporters) : bind and transport solutes across the membrane Channels = pores for solutes to pass through ( no binding occurs) Membrane carbohydrates • Form the glycocalyx = a fuzzy, sticky outer covering Proteoglycans : are mostly carbohydrate Glycoproteins :a re mostly protein Glycolipids • Functions : – Lubrication and protection – Anchoring and locomotion – Specific binding and reception
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This note was uploaded on 12/29/2011 for the course BIOLOGY 24011 taught by Professor Pan during the Fall '11 term at HCCS.

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BIOL&251Ch3Notes - Living organisms are made of one or more cells A cell is the smallest unit of life(that performs all vital physiological

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