TRANSPORT AND THE CELL MEMBRANE 1 Transport Involves

TRANSPORT AND THE CELL MEMBRANE 1

Transport: Involves the absorption and circulation of materials through out an organism • Absorption - process by which dissolved solids and gases enter the cells of an organism. (Through cell membrane) 2

Transport Circulation – is accomplished by: 1. Diffusion of molecules across a membrane and into the organism 2. Cyclosis - streaming of the cytoplasm 3. Movement through the Endoplasmic Reticulum 4. Fluids that flow through tubes or vascular tissue 3

Cell Membrane Structure Protein Molecule Carbohydrate Protein Molecule Protein Channel Lipid Bilayer 4

About the Cell Membrane Fluid mosaic model - the plasma membrane is composed of a double lipid layer in which large proteins float. The cell membrane selectively regulates the entry and exit of materials. • Maintains homeostasis • Selectively permeable membrane • Semi-permeable membrane 5

Function of the Cell Membrane Transport through the cell membrane may be passive or active. Passive Transport - materials move through cell membrane from a region of high concentration to low concentration Hyperlink to Diffusion No energy needed – the movement results from the random motion of particles 6

High Concentration Diffusion Low Concentration Diffusion - movement of molecules from high to low concentration by random movement (Down the concentration gradient). Dynamic Equilibrium is reached when the molecules spread out evenly on either side of a membrane. Molecules will move back and forth but there will be no net change. 7

Diffusion 8

Osmosis The diffusion of water molecules through a membrane from a region of high to low concentration. Molecules that dissolve in water (solute) have an effect on water concentration 9

Which process is occurring in each of the pictures below? 1 2 Diffusion Osmosis 10

Osmosis Terms Solute – something that dissolves in a fluid. Solvent – the fluid (usually water) that a solute dissolves in. 11

Hypertonic Solution A solution that has more solute (dissolved material) relative to another. Ex: Salt Solution 12

Hypotonic Solution A solution that has less solute (dissolved material) relative to another. Ex: Pure Water 13

Isotonic Solution A solution that has equal solute (dissolved material) relative to another. Ex: “Saline” Solution in hospital IVs. 14

Isotonic Solution 15

Plasmolysis The shrinking of a cell due to outward osmosis. 16

Lysis (Animal Cell) Turgid (Plant Cell) Lysis – Rupturing of a cell membrane due to the inward movement of water. Turgid – Vacuole fills with water, pressing the membrane against the cell wall. 17

Water balance between cells and their surroundings is crucial to organisms ISOTONIC SOLUTION HYPOTONIC HYPERTONIC SOLUTION Osmosis causes cells to shrink in a hypertonic solution and swell in a hypotonic solution The control of water balance (osmoregulation) is essential for organisms 18

Types of Cell Environments 19

Facilitated Diffusion Carrier proteins form channels for diffusion of certain molecules. 20

Thought Questions • What happens when you put salt on a slug? 21

Thought Questions • Why do grocery stores spray fruits and vegetables with water? 22

Thought Questions • What happens when you put sugar on strawberries? • (Water will move from a hypotonic to a hypertonic solution) 23

Active transport Process in which energy (ATP) is used to move particles through a membrane. Movement is generally from low to high concentration. (Against the concentration gradient) High Concentration Low Concentration 24

Sodium Potassium Pump 25

Pinocytosis (Endocytosis) Vacuoles, which form at the cell surface, by pinching in, bring in large dissolved molecules. 26

Phagocytosis The cell engulfs large undissolved molecules by forming pseudopods, that surround them. 27

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Four Long Islanders Charged In Deadly Hazing 29