Anatomy Chapter 2.docx

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University of Toronto Scarborough
Biological Sciences
Connie Soros

Chapter 2 Cell Physiology • Cell basics - typical human cell 10-20 m in diameter (m = micrometer, 1/1000 mm, 1/1,000,000 m) - most cells have 3 major subdivisions 1. plasma membrane (cell membrane) a. defines inside/outside b. intracellular fluid (ICF) - inside cell c. extracellular fluid (ECF) - outside cell d. selectively permeable - controls movement of molecules between ICF and ECF 2. nucleus a. usually near cell center b. double layered membrane c. contains DNA, "genetic blueprint," directs protein synthesis, control center of cell (see also appendix C for review) 3. cytoplasm a. area between nucleus and plasma membrane b. contains organelles (1) separation of chemical reactions (2) specialized for a particular function c. cytosol is semiliquid, site of chemical reactions • Organelles (see table Summary of Cytoplasm Components) - endoplasmic reticulum (ER) 1. interconnected fluid-filled membranous system 2. two types a. smooth - interconnected tubules b. rough - interconnected flattened sacs (1) has ribosomes which help in protein synthesis (cell also has "free" ribosomes floating in cytosol) 3. rough ER a. synthesizes proteins and lipids, releases them to ER lumen (1) some will be secreted from the cell (hormones, enzymes), some will become new membrane for the cell or its organelles, or other protein parts of organelles (2) once in the lumen the protein can be modified (pieces removed, sugars added) 4. smooth ER a. in most cells it packages and transports products of rough ER (sections pinch off and become transport vesicles, move to Golgi complex) b. some cells have extensive specialized smooth ER (1) lipid synthesis (steroid hormone secreting cells) (2) detoxify harmful substances (liver cells) (3) store calcium (muscle cells) - Golgi complex 1. layers of flattened membranous sacs (cisternae) 2. processes ER products into final form 3. sorts and sends products to appropriate place a. transport vesicles take products to locations in or outside cell, coating made up of proteins that recognize the product and its destination b. secretory vesicles transport products out of specialized cells, fuses with plasma membrane (secretion, exocytosis) - lysosomes 1. membranous sacs containing hydrolytic enzymes 2. digest cellular debris and foreign substances (old organelles, bacteria) a. material from outside cell can be brought in to be digested by lysosome - endocytosis (membrane surrounds substance and vesicle pinches off) (1) pinocytosis - fluids, "cell drinking" (2) phagocytosis - large particles, "cell eating" b. cell can use digested material - peroxisomes 1. membranous sacs containing oxidative enzymes a. use oxygen to remove hydrogen from molecules (detoxify wastes and foreign chemicals like alcohol) - mitochondria 1. have double membrane a. inner membrane has folds called cristae (folds increase surface area) b. matrix is gel inside 2. converts energy from food into usable energy for the cell - ATP (adenosine triphosphate) a. energy in chemical bonds of food molecules can't be used directly b. ATP  ADP +P + uieful energy 3. three major steps in forming ATP (called cellular respiration) a. glycolysis (1) in cytosol (2) glucose  2 pyruvic acid (a series of steps) (3) yields 2 ATP/glucose (not very efficient by itself) (4) attach H to carrier molecules b. citric acid cycle (also called Krebs cycle or tricarboxylic acid cycle) (1) pyruvic acid is transported to mitochondrial matrix (2) pyruvic acid  acetyl CoA (3) acetyl CoA enters citric acid cycle, which is a series of reactions (4) CO 2s produced + (5) hydrogen atoms are attached to carrier molecules (NAD , nicotinamide adenine dinucleotide; FAD, flavine adenine dinucleotide; become NADH and FADH ) 2 (6) 2 more ATP/original glucose c. electron transport chain (1) occurs on inner mitochondrial membrane which contains electron carrier molecules (each H contains one electron, moving electrons means moving energy) (2) NADH and FADH from2glycolysis and citric acid cycle enter chain, the electron is removed from each H and passed through the series of electron carriers
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