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Homeostasis Standard SB1. Students will analyze the nature of the relationships between structures and functions in living cells. a. Explain the role of cell organelles for both prokaryotic and eukaryotic cells, including the cell membrane, in maintaining homeostasis and cell reproduction. d. Explain the impact of water on life processes (i.e., osmosis, diffusion) Essential Question How does the cell membrane help maintain homeostasis? What is Homeostasis The ability of the body, or a cell, to maintain a constant internal environment in response to external changes. Examples: Body temperature 98.6 degrees Shiver when cold Sweat when hot Apoptosis Cell self destructs in response to stress Keeps issues within that cell from spreading to other cells Hormone signals Release of insulin in response to high glucose levels This reduces high blood sugar Epinephrine-increases heart rate, muscle strength, and sugar metabolism Cortisol-increases sugar in bloodstream Cell membrane and homeostasis Cell membrane Phospholipid bilayer Selectively permeable controls what goes in an out of cell thru channels, carriers and pumps Water flows freely by diffusion Controls hormone release, nutrient flow, and water flow Two ways thru: Passive transport High concentration to low concentration Active transport Low concentration to high concentration Requires energy Passive Transport Two types Diffusion Facilitated diffusion Facilitated Diffusion Examples: Glucose entering the cell for respiration Amino acids entering and leaving the cell for protein synthesis Diffusion Examples: Gas exchange for photosynthesis carbon dioxide from air to leaf, oxygen from leaf to air. Gas exchange for respiration oxygen from blood to tissue cells, carbon dioxide in Water sucked up by roots Osmosis Diffusion Example Active Transport Three types Endocytosis Exocytosis Ion pumps Endocytosis Examples Pinocytosis (‘cell drinking’) Uptake of large molecules (DNA, protein) from solution Phagocytosis (‘cell eating’) Uptake of solid particles by a cell Amoebas feeding Phagocytes engulfing bacteria. Exocytosis Examples Protein packaging into vesicles and delivery to other cells Removal of waste Ion pumps Examples Re-absorption of glucose, amino acids and salts by the kidneys. Sodium/potassium pump in cell membranes (especially nerve cells) Ion pump Let’s Review the details Grab a cell transport worksheet