CELLULAR TRANSPORTThe Cell and its Environment

Cellular Transport

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The Cell in its Environment

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The Cell MembraneSelectively permeable membrane

Lipids

Transport Proteins

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SELECTIVELY PERMEABLE

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Diffusion across cell membrane

INfoodcarbohydratessugars, proteinsamino acidslipidssalts, O2, H2O

OUTwasteammoniasaltsCO2

H2O products

cell needs materials in & products or waste out

IN

OUT

Can it be an impenetrable boundary? NO!

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Channels through cell membrane

inside cell

outside cell

sugaraaH2O

saltNH3

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Cellular TransportTwo Kinds

1. Passive Transport2. Active Transport

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Types of Cellular Transport

high

low

This is gonna

be hard work!!

high

low

Weeee!!!

Passive Transport - cell doesn’t use energy

1.Diffusion

2.Facilitated Diffusion

3.Osmosis

Active Transport - cell uses energy

1.Protein Pumps

2.Endocytosis

3.Exocytosis

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PASSIVE TRANSPORTDiffusion

Facilitated Diffusion

Osmosis

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Passive Transport

Diffusion is the movement of

molecules from an area of higher concentration

to an area of lower concentration.

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Diffusion of Molecules

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Diffusion

Diffusion movement from high low concentration

Diffusion movement from high low concentration

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Facilitated Diffusion•Diffusion through protein channels

• channels move specific molecules across cell membrane

“The Bouncer”

“The Bouncer”

open channel = fast transport

facilitated = with help

high

low

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Passive Transport Comparison

Facilitated diffusion (Channel Protein)

Diffusion (Lipid Bilayer)

Carrier Protein

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OsmosisThe movement of water across a cell membrane

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Isotonicthe concentration of water outside and inside the cell is equal.

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Hypotonic Solution19

Hypotonicthe concentration of water outside the cell is greater than the concentration of water inside the cell; water will flow into the cell, causing it to swell

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Hypotonic Solution21

Solute less than WaterSolute less than Water

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Water moves from the solution to inside of the cell. The cell Swells and bursts open.

Cytolysis is cell bursting.

Hypertonicthe concentration of water outside the cell is lower than the concentration of water inside the cell; therefore water will flow out of the cell, causing it to shrink

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Hypertonic Solution

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Solute greater than Water

Solute greater than Water

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Water moves from inside the cell into the solution and the cell shrinks.

Plasmolysis cell shrinking

Managing water balanceCell survival depends on balancing water

uptake and loss.

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Concentration of Solution•Direction of osmosis is determined by comparing total solute concentrations

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Tonicity

Inside the Cell SolutionMovement of

Water(Cell Condition)Solute Water Solute Water

HypertonicWater goes in

the Cell(Cell Shrivel)

HypotonicWater goes out

the Cell(Cell Bust)

Isotonic Normal Cell

= ===

How Organisms Deal with

Osmotic PressureBacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall is called turgor pressure.

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How Organisms Deal with Osmotic Pressure

•A protist like paramecium has contractile vacuoles that collect water flowing in and pump it out to prevent them from over-expanding.

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How Organisms Deal with Osmotic Pressure

•Salt water fish pump salt out of their specialized gills so they do not dehydrate.

•Animal cells are bathed in blood. Kidneys keep the blood isotonic by remove excess salt and water.

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ACTIVE TRANSPORTProtein Channels

Endocytosis and Exocytosis

Phagocytosis and Pinocytosis

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Active Transport actively moves molecules to

where they are needed Movement molecules from

an area of low concentration to an area of high concentration (Low High)

cell uses energy

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Types of Active Transport

Protein PumpsEndocytosisExocytosis

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Protein Pumps

transport proteins that require energy to do

work

Sodium / Potassium Pumps are important in

nerve responses.

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Endocytosis: taking bulky material into a cell • Uses energy• Cell membrane in-

folds around food particle and forms food vacuole and digest food

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TWO KINDS:1. Phagocytosis – cell enguls

solid particles of food

“cell eating”

2. Pinocytosis – cell takes in droplets of fluid

“ Cell drinking”

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Phagocytosis Pinocytosis

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3. Exocytosis: Forces material out of cell in bulk• membrane surrounding

the material fuses with cell membrane

• Cell changes shape – requires energy

• EX: Hormones or wastes released from cell

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Cytoplasm

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