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Cellular Transport Notes

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The Purpose of the Plasma Membrane is to Maintain an Internal Balance called HOMEOSTASIS or To Reach Dynamic Equilibrium Is traffic at equilibrium? Why or why not?

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Equilibrium occurs when molecules have spread out evenly When the concentration of a solute is equal throughout the solution

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ALL cells have a cell membrane made of proteins and lipids Cell Membrane lipid bilayer protein channel protein pump Layer 1 Layer 2 SOME cells have cell membranes and cell walls ex: plants, fungi and bacteria Cell Membrane Cell Wall

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Components of the Plasma Membrane Phospholipids:ProteinsCholesterol

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Cell Membrane Aka: PhosphoLipid Bilayer: 2 layers of phospholipids2 layers of phospholipids provides a barrier for the cell. Allows for selective permeabilityprovides a barrier for the cell. Allows for selective permeability a. Phosphate head (hydrophilic=water loving) b. Fatty acid tails are non-polar non-polar (hydrophobic=water fearing) Phospholipids Phospholipid Lipid Bilayer http://www.youtube.co m/watch?v=Rl5EmUQd kuI&feature=fvwrel

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Figure 8.9 Some functions of membrane proteins PROTEINS serve many functions for the plasma membrane

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Cholesterol Molecules Makes the bilayer stronger but still flexible Holds two layers together

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Function of the Cell Membrane: Cell membrane separates the components of a cell from its environmentsurrounds the cell Gatekeeper of the cellregulates the flow of materials into and out of cellselectively permeable Cell membrane helps cells maintain homeostasis stable internal balance http://www. pbslearning media.org/r esource/tdc 02.sci.life.c ell.membra neweb/cell- membrane- just- passing- through/

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Passive Transport A process that does not require energy to move molecules from a HIGH to LOW concentration DDiffusion OOsmosis F Facilitated Diffusion

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NO ENERGY NEEDED: Diffusion Osmosis Facilitated Diffusion ENERGY NEEDED: Active Transport ANALOGY:

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Active Transport Active transport is the movement of molecules from LOW to HIGH concentration. Energy is required as molecules must be pumped against the concentration gradient. 3 Types: 1. Protein Pumps 2. Endocytosis 3. Exocytosis outside of cell inside of cell Carbon Dioxide molecules

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Diffusion is the movement of small particles across a selectively permeable membrane like the cell membrane until equilibrium is reached. These particles move from an area of high concentration to an area of low concentration. outside of cell inside of cell

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Where does diffusion take place in the body?

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Facilitated Diffusion is the movement of larger molecules like glucose through the cell membrane larger molecules must be helped Proteins in the cell membrane form channels for large molecules to pass through Proteins that form channels (pores) are called protein channels outside of cell inside of cell Glucose molecules

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diffusion of specific particles through transport proteins found in the membrane a. Transport Proteins are specific they select only certain molecules to cross the membrane Ex: channel or carrier proteins a. Transports larger or charged molecules Facilitated diffusion (Carrier Protein) AB Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer)

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Osmosis is the diffusion of water through a selectively permeable membrane like the cell membrane Water diffuses across a membrane from an area of high concentration to an area of low concentration.

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Types of Solution Concentrations that cause molecules to move 1. Hypertonic 2. Hypotonic 3. Isotonic

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Hypertonic Solutions: contain a high concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypertonic solution, the water diffuses out of the cell, causing the cell to shrivel.

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Isotonic Solutions: contain the same concentration of solute as another solution (e.g. the cell's cytoplasm). When a cell is placed in an isotonic solution, the water diffuses into and out of the cell at the same rate. The fluid that surrounds the body cells is isotonic.

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Hypotonic Solutions: contain a low concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypotonic solution, the water diffuses into the cell, causing the cell to swell and possibly explode.

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Figure 8.12 The water balance of living cells HYPO= MoreISO = Equal HYPER = More

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ACTIVE TRANSPORT GOES AGAINST CONCENTRATION GRADIENT = NEEDS ATP ENERGY

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1. Protein Pumps -transport proteins that require energy to do work Protein changes shape to move molecules: this requires energy! Example: Sodium / Potassium Pumps are important in nerve responses.

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Food is moved into the cell by Endocytosis Wastes are moved out of the cell by Exocytosis Endocytosis and Exocytosis is the mechanism by which molecules (such as food and wastes) get into and out of the cell

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1. Phagocytosis- cell eating Extensions of the cytoplasm surround a particle and package it within the vacuole 2 Types of Endocytosis

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2. Pinocytosis- cell drinking Pockets form along the cell membrane, fill with liquid, and pinch off to form vacuoles within the cell 2 Types of Endocytosis