Biology Chapter 7.31 Homeostasis and cell transport Biology class Pg A macrophage consuming a fungal spore shows off modo's subsurface

Key Terms Diffusion Facilitated diffusion Osmosis Isotonic Hypertonic Osmotic pressure Active transport Passive transport Homeostasis Endocytosis Exocytosis Hypotonic Equilibrium Contractile vacuole Plasmolysis Cytolysis Pinocytosis Phagocytosis Concentration gradient Biology- chapter 5 notes2

3 What to know E xplain how an equilibrium is established as a result of diffusion. Distinguish between diffusion and osmosis. Explain how substances cross the cell membrane through facilitated diffusion. Explain how ion channels assist the diffusion of ions across the cell membrane. Distinguish between passive and active transport. Compare endocytosis and exocytosis

Biology- chapter 5 notes4 Q and A Q:What is phagocytosis? A: phago+ to eat, cyto = cell Q: How this kind of phagocytosis is useful to animal. (96) A: the immune system cells may stop tumors from growing Q: What is Energy? Potential and Kinetic A: ability to do work, stored E, in motion E Q: 2 main components of cell membranes A: lipids and proteins Q: What does it mean to say a cell is selectively permeable? A: Only some substances can cross the membrane

Biology- chapter 5 notes5 Passive Transport Homeostasis –the maintenance of a stable level of internal conditions even though environmental conditions are constantly changing. (temp, water content, pH) Cell membranes help organisms maintain homeostasis by controlling what substances may enter or leave cells. Some substances can cross the cell membrane without any input of energy by the cell in a process know as passive transport.

Biology- chapter 5 notes6 Types of Passive Transport 1.Diffusion 2.Osmosis 3.Facilitated diffusion 4.Diffusion through ion channels

Biology- chapter 5 notes7 1. Diffusion Is the movement of molecules from one area of higher concentration to an area of lower concentration. The difference in the concentration of molecules across a distance is called a concentration gradient. It is driven by kinetic energy of molecules (constant motion) Move from [High] to [low] or down the gradient Equilibrium when the concentration of the molecules are the same throughout the space

Biology- chapter 5 notes8 Diffusion across a membrane Cell membranes allow some molecules to pass through- but not all Goes from high to low- simple diffusion till it reaches an equilibrium Diffusion of molecules depends on: 1.Size and type of molecule 2.Chemical nature 3.Polar or nonpolar- (carbon dioxide and oxygen are nonpolar dissolve in lipids)

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Biology- chapter 5 notes11 2. Osmosis Water molecules diffuse across a cell membrane from [H] to [L] Osmosis does not require cells to expend energy (passive) Directions: 1.HypOtonic- water is higher on outside- swell 2.Hypertonic-water is higher inside cell- shrink 3.Isotonic-at equilibrium

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Biology- chapter 5 notes14 How cells deal with Osmosis If they are in a isotonic environment – no difficulty keeping movement of water If in a hypotonic environment- water is constantly diffuses into these organisms- they use a contractile vacuoles to rid the excess water- this pumping action requires energy and is not passive 3 reactions to environments: 1. Turgor pressure- pressure of water pushing cell walls, swelling 2. Plasmolysis- loss of water, cell shrink, plant wilt 3. Cytolysis- bursting of a cell

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Biology- chapter 5 notes19 3. Facilitated Diffusion Used in molecules that can not easily diffuse through cell membranes May be too large or not soluble in lipids Special proteins called carriers (specific) will assist the molecules across- molecules attached themselves to the carriers and are brought into the cells (glucose is too large)

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Biology- chapter 5 notes21 4. Diffusion through ion channels Transport ions from [H] to [L] They are not soluble in lipids and can not be passed in the membranes- must travel through the specific channels The channels can have gates to allow some ions to pass and keep others out

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Biology- chapter 5 notes23 Active Transport In many cases, cells must move materials from an area of lower concentration to an area of higher concentration, or “up” their concentration gradient. Such movement of materials is know as active transport. Unlike passive transport, AT requires a cell to expend ENERGY.

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Biology- chapter 5 notes25 Cell membrane pumps Move substance from Lower to Higher concentrations- requires energy (going up a hill requires work) Sodium-potassium pump-in animals and used a carrier protein; organisms need a high [Na+] outside the cell while having higher [K+] inside the cells; this pump maintains the differences ges/active%20transport.htm

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Biology- chapter 5 notes27 Movement in Vesicles Some molecules are too large to pass through the cell membrane- How do you get the larger molecules into the cells? Two ways 1. endocytosis 2 exocytosis

Biology- chapter 5 notes28 1. Endocytosis- In cell The process by which cells ingest external fluid, macromolecules, and large particles Materials are enclosed by a portion of the cell’s membrane than the pouch pinches off from the cells and becomes a membrane-bound organelle called a vesicle. Two types: 1. Pinocytosis- solutes or fluids (drinking cell) 2. Phagocytosis- large particles, whole cells (eating cell) Phagocytes- are organisms that used phagocytosis

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Biology- chapter 5 notes30 Phagocytosis- Pinocytosis

Biology- chapter 5 notes31 2. Exocytosis- out cell The process by which a substance is released from the cell through a vesicle that transports the substance out of the cell Used to release large molecules such as proteins, waste products or toxins Demo:

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Biology- chapter 5 notes35 Do you know? 1.4 types of passive transport 2. Types of active transport 3. Active vs. Passive

websites Interactive transport – /animations/membrane_transport/m embrane_transport.htmhttp:// /animations/membrane_transport/m embrane_transport.htm Lab bench – ce/labbench/lab1/intro.htmlhttp:// ce/labbench/lab1/intro.html Conditions - nce/virtual_labs/LS03/LS03.htmlhttp:// nce/virtual_labs/LS03/LS03.html Biology- chapter 5 notes36