Active Transport, Active Transport, Exocytosis and Exocytosis and

EndocytosisEndocytosis

Chapter 3, Section 5Chapter 3, Section 5

Of your textbookOf your textbook

Active TransportActive Transport

Moves substances Moves substances AGAINSTAGAINST their their concentration gradientconcentration gradient From areas of low concentration to areas of From areas of low concentration to areas of

high concentrationhigh concentration

Active Transport Needs EnergyActive Transport Needs Energy

Active transport Active transport is an “uphill” is an “uphill” process (low process (low hi) – the opposite hi) – the opposite of passive of passive transporttransportTherefore, active Therefore, active transport requires transport requires energy from ATPenergy from ATP

Active Transport & Membrane ProteinsActive Transport & Membrane Proteins

Active transport uses Active transport uses transport proteinstransport proteins, often , often called called pumpspumps, to move , to move substances across the substances across the membranemembrane These membrane These membrane

proteins are proteins are integralintegral proteins – they extend all proteins – they extend all the way through the the way through the membranemembrane

They use ATP to pump They use ATP to pump molecules / ions against molecules / ions against their concentration their concentration gradientsgradients

Transport ProteinsTransport Proteins

Most transport proteins change shape Most transport proteins change shape when they bond with the target molecule(s).when they bond with the target molecule(s).

Some bond to only Some bond to only oneone type of molecule (= type of molecule (= uniportuniport) and move that molecule in ) and move that molecule in oneone direction (animation)direction (animation)

Proton PumpProton Pump

The proton pump The proton pump is an example of a is an example of a uniport transport uniport transport protein.protein.

This pump is found This pump is found in the membranes in the membranes of certain of certain organelles.organelles.

It moves protons It moves protons (H+) into the (H+) into the organelle.organelle.

Transport ProteinsTransport Proteins

Others bond to two Others bond to two types of moleculestypes of molecules May move the May move the

molecules in the molecules in the samesame direction (= direction (= symportsymport))

May move the May move the molecules in molecules in oppositeopposite directions (= directions (= antiportantiport)) Symport animation

Antiport animation

Sodium-Potassium PumpSodium-Potassium Pumpclick on title for animationclick on title for animation

An example of an An example of an antiportantiport transport protein. transport protein.

Moves three sodium ions (Na+) out of the cell for Moves three sodium ions (Na+) out of the cell for every two potassium ions (K+) it moves inevery two potassium ions (K+) it moves in

Important for re-establishing “normal” conditions Important for re-establishing “normal” conditions after a nerve impulse / action potentialafter a nerve impulse / action potential

EndocytosisEndocytosisclick on title for animation on Endo/Exocytosisclick on title for animation on Endo/Exocytosis

A method for bringing large A method for bringing large molecules into a cellmolecules into a cell

Molecules are engulfed by the Molecules are engulfed by the cell membrane.cell membrane. A pocket is made around the A pocket is made around the

substance to be taken insubstance to be taken in The pocket breaks off inside the The pocket breaks off inside the

cell and forms a vesiclecell and forms a vesicle The vesicle fuses with a lysosome The vesicle fuses with a lysosome

or other organelleor other organelle

Requires energy from ATPRequires energy from ATP

PhagocytosisPhagocytosisclick on title for animationclick on title for animation

Type of endocytosisType of endocytosis

The cell membrane engulfs larger, solid The cell membrane engulfs larger, solid particles particles Literally means “cell eating”Literally means “cell eating”

Example: Amoeba take in / engulf their food through phagocytosis.

PhagocytosisPhagocytosis

In the human immune system, some white In the human immune system, some white blood cells (called macrophages) engulf blood cells (called macrophages) engulf and destroy foreign material, such as and destroy foreign material, such as bacteria, through phagocytosisbacteria, through phagocytosis

PinocytosisPinocytosis

Type of endocytosisType of endocytosis

The cell takes in fluid (which may also The cell takes in fluid (which may also contain some dissolved substances)contain some dissolved substances) Literally means “cell-drinking”Literally means “cell-drinking”

Example: Fluid may cross the membrane of a blood vessel through pinocytosis.

ExocytosisExocytosis

The opposite of endocytosisThe opposite of endocytosis

Substances are released by Substances are released by a cell through a vesicle that a cell through a vesicle that carries the unwanted carries the unwanted substance and fuses with substance and fuses with the membranethe membrane

Once it fuses with the Once it fuses with the membrane, the vesicle membrane, the vesicle releases the substance releases the substance outside the celloutside the cell

ExocytosisExocytosis

Neurotransmitters – Neurotransmitters – chemical signals in your chemical signals in your nervous system - are nervous system - are released from nerve cell released from nerve cell to nerve cell in this to nerve cell in this mannermanner

When the Golgi When the Golgi apparatus modifies apparatus modifies proteins and sends them proteins and sends them out of the cell, it uses out of the cell, it uses exocytosis.exocytosis.