Chapter 3 - Chapter 3 - An Introduction to Cells

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Chapter 3 - An Introduction to Cells Cell Theory - developed from Robert Hooke’s research Cells are the building blocks of all plants and animals All cells come from the division of preexisting cells Cells are the smallest units that perform all vital physiological functions Each cell maintains homeostasis at the cellular level Sex cells  (germ cells) - Reproductive cells  Somatic cells  (soma = body): all body cells except sex cells A cell is surrounded by a watery medium known as the extracellular fluid (interstitial fluid) Plasma membrane (cell membrane) separates cytoplasm from the extracellular fluid  Cytoplasm  - Cytosol = liquid; intracellular structures collectively known as organelles  Plasma Membrane - Functions of the Plasma Membrane i. Physical isolation: barrier    ii. Regulates exchange with environment: released iii. Monitors the environment: extracellular fluid composition; chemical signals  iv. Structural support: anchors cells and tissues Membrane Lipids  - double layer of  phospholipid  molecules 0. Hydrophilic heads—toward watery environment, both sides 1. Hydrophobic fatty-acid tails—inside membrane  2. Barrier to ions and water—soluble compounds Membrane Proteins Integral proteins - within the membrane  Peripheral proteins - bound to inner or outer surface of the membrane Functions of Membrane Proteins i. Anchoring proteins (stabilizers) - attach to inside or outside structures  ii. Recognition proteins (identifiers) - label cells as normal or abnormal  iii. Enzymes - catalyze reactions  iv. Receptor proteins - bind and respond to ligands (ions, hormones)  v. Carrier proteins - transport specific solutes through membrane  vi. Channels – regulate water flow and solutes through membrane    Membrane Carbohydrates: proteoglycans, glycoproteins & glycolipids; extend outside cell membrane; form sticky “sugar  coat” ( glycocalyx ); functions of the glycocalyx Lubrication and protection Anchoring and locomotion Specificity in binding (receptors) Recognition (immune response) Organelles and the Cytoplasm - all materials inside the cell and outside the nucleus   Cytosol  (fluid) - dissolved materials: nutrients, ions, proteins, and waste products  High potassium/low sodium; High protein; High carbohydrate/low amino acid and fat Organelles  - structures with specific functions Nonmembranous organelles - no membrane; direct contact with cytosol; includes cytoskeleton, microvilli, centrioles,  Membranous organelles - covered with plasma membrane; isolated from cytosol; includes endoplasmic reticulum (ER), 
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This note was uploaded on 07/13/2011 for the course BIOL 2401 taught by Professor Watson during the Summer '10 term at Richland Community College.

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Chapter 3 - Chapter 3 - An Introduction to Cells

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