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Gateway to the CellGateway to the Cell

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Protective barrierProtective barrier

Regulate transport in & out of Regulate transport in & out of cell cell (selectively permeable)(selectively permeable)

Allow cell recognitionAllow cell recognition

Provide anchoring sites for Provide anchoring sites for filaments filaments of cytoskeletonof cytoskeleton

Balanced internal condition of cells

Also called equilibrium Maintained by cell

membrane controlling what enters & leaves the cell

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Polar heads are hydrophilichydrophilic “water loving”

Nonpolar tails are hydrophobichydrophobic “water fearing”Makes membrane “Selective” in what crosses

Hydrophobic molecules pass easily; hydrophilic DO NOT

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PASSIVE TRANSPORTACTIVE TRANSPORT

Does not require energy.

Move particles from an area of high concentration to an area of low concentration

Examples: osmosis and diffusion

Requires Energy Moves particles

from an area of low concentration to an area of high concentration

Examples:endocytosis and exocytosis

Movement of particles from an area of high concentration to an area of low concentration

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Cell membrane

Solute moves DOWN concentration gradient (HIGH to LOW)

copyright cmassengale 10

Molecules will randomly move Molecules will randomly move through the through the porespores in in Channel Channel ProteinsProteins..

Diffusion of Diffusion of waterwater across a across a membranemembrane

Moves from Moves from HIGH water HIGH water potential to potential to LOW water LOW water potentialpotential

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Diffusion across a membrane

Semipermeable

membrane

Exocytosis- moving large things out

Endocytosis- Moving large things in

Pinocytosis- Drinking of the cell Phagocytosis- Eating of the cell

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PinocytosisPinocytosis

--Takes in dissolved Takes in dissolved molecules as a vesiclemolecules as a vesicle.

“Cell Drinking”

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Endocytosis – Phagocytosis Endocytosis – Phagocytosis

Used to Used to engulf large particlesengulf large particles such such as food, as food, bacteriabacteria, etc. into vesicles, etc. into vesicles

Called Called “Cell Eating”“Cell Eating”

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Phagocytosis About to OccurPhagocytosis About to Occur

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PhagocytoPhagocytosissis - Capture of a Yeast Cell by Membrane Extensions of an Immune System Cell

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ExocytosisExocytosis The opposite of endocytosis is exocytosis. The opposite of endocytosis is exocytosis. Large moleculesLarge molecules that are manufactured in that are manufactured in

the cell are the cell are releasedreleased through the cell through the cell membranemembrane..

Inside Cell Cell environment

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Moving the “Big Stuff”Moving the “Big Stuff”

Molecules are Molecules are moved outmoved out of the cell by of the cell by vesiclesvesicles that that fusefuse with the plasma membrane. with the plasma membrane.

ExocytosiExocytosiss-

moving things out.

This is how many This is how many hormoneshormones are secreted and how are secreted and how nerve cellsnerve cells communicate with one another communicate with one another.

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CELLCELL

10% NaCL90% H2O

10% NaCL

90% H2O

What is the direction of water movement?The cell is at _______________.equilibrium

ENVIRONMENTENVIRONMENT

NO NET NO NET MOVEMENMOVEMENTT

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CELLCELL

10% NaCL90% H2O

20% NaCL

80% H2O

What is the direction of water movement?

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CELLCELL

15% NaCL85% H2O

5% NaCL95% H2O

What is the direction of water movement?

ENVIRONMENTENVIRONMENT

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Isotonic Solution

NO NET MOVEMENT OF

H2O (equal amounts entering

& leaving)

Hypotonic Solution

Hypertonic Solution

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IsotonicIsotonic Hypotonic

Hypertonic

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hypotonic hypertonic isotonic

hypertonic isotonic hypotonic

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Transport Across the MembraneTransport Across the Membrane

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Passive Passive TransportTransport

Facilitated diffusion

Doesn’t require energy

Uses transport proteins to move high to low concentrationExamples: Examples: GlucoseGlucose or or amino acidsamino acids moving moving from blood into a from blood into a cell.cell.

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Active TransportActive Transport

Requires energy or ATP

Moves materials from LOW to HIGH concentration

AGAINST concentration gradient