Types of Transport Types of Transport Across Cell Across Cell MembranesMembranes

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Passive Transport

▪ Does not require energy▪ Substances move from high to low▪Solutes move down the concentration gradient ▪Examples: oxygen, water, carbon dioxide

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Types of Passive Transport

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DiffusionDiffusion

▪Movement of substances (except water) across a cell membrane

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Diffusion of LiquidsDiffusion of Liquids

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OsmosisOsmosis

▪Diffusion of Diffusion of water across a water across a membranemembrane

▪Moves from Moves from HIGH water HIGH water concentration concentration (low solute) to (low solute) to LOW water LOW water concentration concentration (high solute)(high solute)

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Diffusion across a membrane

Semipermeable

membrane

Diffusion of HDiffusion of H22O Across A O Across A MembraneMembrane

▪High water potential = low solute concentration▪Low water potential = low solute concentration

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3 Types of solutions

▪Isotonic▪Hypotonic▪Hypertonic

▪THINK IN TERMS OF SOLUTE CONCENTRATION NOT WATER CONCENTRATION!!!!

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Cell in Isotonic SolutionCell in Isotonic Solution

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CELLCELL

10% NaCL90% H2O

10% NaCL

90% H2O

The cell is at _______________.equilibrium

ENVIRONMENTENVIRONMENT

NO NET NO NET MOVEMENMOVEMENTT

Cell in Hypotonic SolutionCell in Hypotonic Solution

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CELLCELL

10% NaCL90% H2O

20% NaCL

80% H2O

What is the direction of water movement?

Cell in Hypertonic Cell in Hypertonic SolutionSolution

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CELLCELL

15% NaCL85% H2O

5% NaCL95% H2O

What is the direction of water movement?

ENVIRONMENTENVIRONMENT

Ways to Remember Solutions

▪ “SALT SUCKS”▪ Water wants to join the party

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Think about it:

▪ Why do you cook onions before you salt them?

▪Why did pioneers use salt to cure their meats (remember no refrigerators)

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Cytolysis & Cytolysis & PlasmolysisPlasmolysis

▪Cytolysis – Cells swell and burst

▪Plasmolysis – Cells shrink and shrivel

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Osmosis in Red Blood CellsOsmosis in Red Blood Cells

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IsotonicIsotonic Hypotonic

Hypertonic

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hypotonic hypertonic isotonic

hypertonic isotonic hypotonic

Facilitated DiffusionFacilitated Diffusion

▪Doesn’t require energy

▪Uses transport proteins to move material from a high to low concentration▪Examples: Glucose or Examples: Glucose or amino acids moving from amino acids moving from blood into a cell.blood into a cell.

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Proteins Are Critical to Proteins Are Critical to Membrane FunctionMembrane Function

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Types of Transport ProteinsTypes of Transport Proteins

▪Channel proteins are embedded in the cell membrane & have a pore for materials to cross ▪Carrier proteins can change shape to move material from one side of the membrane to the other

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Channel Proteins

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Carrier ProteinsCarrier Proteins

▪Carrier Carrier proteins proteins change shape change shape to move to move materials materials across the across the cell cell membranemembrane

Active TransportActive Transport

▪Requires energy or ATP

▪Moves materials from LOW to HIGH concentration

▪AGAINST concentration gradient

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Active transport ExampleActive transport Example

▪Sodium/ Potassium pump▪Pumping Na+ (sodium ions) out and K+ (potassium ions) in against strong concentration gradients.

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Sodium-Potassium Sodium-Potassium PumpPump

Types of Active Transport

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Exocytosis

▪Molecules moved out of the cell

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ExocytosisExocytosisExocytic Exocytic vesicle vesicle immediately immediately after fusion after fusion with plasma with plasma membrane.membrane.

Endocytosis

▪Molecules moved into of the cell▪2 types

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Pinocytosis

▪Most common form▪Moves dissolved molecules into cell▪Cell “drinking”

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Example of Example of PinocytosisPinocytosispinocytic vesicles forming mature transport vesicle

Transport across a capillary cell (blue).

Phagocytosis

▪Used to engulf large molecules to bring into cell▪Cell “eating”

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Phagocytosis About to OccurPhagocytosis About to Occur

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PhagocytoPhagocytosissis - Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue)