Moving through the Plasma Membrane

What does a phospholipid look like?

Let’s Review

• What is homeostasis?

• What is the job of the plasma membrane?

• How do you think the cell membrane helps a cell maintain homeostasis?

What does the Plasma Membrane look like?

GlycoproteinProtein

CholesterolPhospholipids

Outside Cell (Extracellular Matrix)

Inside Cell (Cytoplasm)

The Plasma Membrane

GlycoproteinProtein

CholesterolPhospholipids

Outside Cell (Extracellular Matrix)

Inside Cell (Cytoplasm)

The Plasma Membrane

Glycoprotein

Protein

CholesterolPhospholipids

Outside Cell (Extracellular Matrix)

Inside Cell (Cytoplasm)

Non-Polar Polar

Plasma Membrane:The Fluid Mosaic Model

• Fluid because–the phospholipid and protein

molecules are able to move around. Not stuck in one place.

• Mosaic because– the membrane contains a variety

of proteins embedded with the phospholipids.

Plasma Membrane:The Fluid Mosaic Model

How do particles move in and out of the cell?

Passive Transport•No additional _______________

is required because every particle has its own energy

•This energy produces ________________ movement in particles. (a.k.a Brownian motion)

energy

random

Diffusion•Diffusion is the movement of

substances from a ________ concentration to a low concentration.

•Diffusion is caused by __________ __________

•Concentration is the _________ of something in a given ______.

Brownian Motion

high

amountarea

How does it work?•Particles move down the concentration gradient, until the concentration is _________ throughout an area.

•Then the system is said to have reached dynamic equilibrium.

equal

High Concentration of Blue Dots

Low Concentration of Orange Dots

High Concentration of Orange Dots

Low Concentration of Blue Dots

System has reached dynamic equilibrium

A.

B.

Examples of diffusion at work

• Why does food smell fragrant when cooked?

• Have you ever stood next to someone wearing strong perfume?

Permeability of a membranePermeability of a membrane

• Permeable: anything can pass through

• Semi-permeable: some things can pass through

• Impermeable: nothing can pass through

Outside Cell (Extracellular Matrix)

Inside Cell (Cytoplasm)

Back to the plasma membrane…

• The plasma membrane is described as semi-permeable because some substances can move through it:

–Small and

–Non-polar

Osmosis

•Diffusion of _________ across a membrane

•Water molecules can pass through pores or openings created by __________ in the plasma membrane .

water

proteins

Glycoprotein

Protein

Cholesterol Phospholipids

Outside Cell (Extracellular Matrix)

Inside Cell (Cytoplasm)

Back to the plasma membrane…

The Cell’s Environment: Isotonic

•In an isotonic environment the solute concentrations are ___________ and there is no NET movement of water.

equal

The Cell’s Environment: Hypotonic

•In a hypotonic environment, there are __________ solutes outside than inside and water moves into the cell.

less

The Cell’s Environment: Hypertonic

•In a hypertonic environment there are _________ solutes outside than inside and water moves out of the cell.

more

Environment outside cell

Water moves…

Effect on ANIMAL cell

Effect on PLANT cell

Hypotonic

Hypertonic

Isotonic

Environment outside cell

Water moves…

Effect on ANIMAL cell

Effect on PLANT cell

Hypotonic In Swells, then bursts (cytolysis)

Hypertonic

Isotonic

Animal Cell Cytolysis

Cell still intact

Cells burst

Environment outside cell

Water moves…

Effect on ANIMAL cell

Effect on PLANT cell

Hypotonic In Swells, then bursts (cytolysis)

Swells, increases turgor pressure

Hypertonic

Isotonic

Environment outside cell

Water moves…

Effect on ANIMAL cell

Effect on PLANT cell

Hypotonic In Swells, then bursts (cytolysis)

Swells, increases turgor pressure

Hypertonic Out

Isotonic

Environment outside cell

Water moves…

Effect on ANIMAL cell

Effect on PLANT cell

Hypotonic In Swells, then bursts (cytolysis)

Swells, increases turgor pressure

Hypertonic out Shrinks (crenation)

Isotonic

Environment outside cell

Water moves…

Effect on ANIMAL cell

Effect on PLANT cell

Hypotonic In Swells, then bursts (cytolysis)

Swells, increases turgor pressure

Hypertonic out Shrinks (crenation)

Shrink (plasmolysis)

Isotonic

Environment outside cell

Water moves…

Effect on ANIMAL cell

Effect on PLANT cell

Hypotonic In Swells, then bursts (cytolysis)

Swells, increased turgor pressure

Hypertonic Out Shrinks

(crenation)

Shrinks, (plasmolysis)

Isotonic

Environment outside cell

Water moves…

Effect on ANIMAL cell

Effect on PLANT cell

Hypotonic In Swells, then bursts (cytolysis)

Swells, increases turgor pressure

Hypertonic out Shrinks (crenation)

Shrink (plasmolysis)

Isotonic

Plant cell: Plasmolysis

Normal cells

Plasmolyzed Cells

Environment outside cell

Water moves…

Effect on ANIMAL cell

Effect on PLANT cell

Hypotonic In Swells, then bursts (cytolysis)

Swells, increases turgor pressure

Hypertonic out Shrinks (crenation)

Shrink (plasmolysis)

Isotonic In and out at the same rate

Environment outside cell

Water moves…

Effect on ANIMAL cell

Effect on PLANT cell

Hypotonic In Swells, then bursts (cytolysis)

Swells, increases turgor pressure

Hypertonic out Shrinks (crenation)

Shrink (plasmolysis)

Isotonic In and out at the same rate

Stays the same

Environment outside cell

Water moves…

Effect on ANIMAL cell

Effect on PLANT cell

Hypotonic In Swells, then bursts (cytolysis)

Swells, increases turgor pressure

Hypertonic out Shrinks (crenation)

Shrink (plasmolysis)

Isotonic In and out at the same rate

Stays the same

Stays the same

Osmosis in Action•What happens when you

sprinkle salt on a slug?•If you are stranded at sea and

run out of water, should you drink sea water?

** Water moves from a hypo to a hypertonic environment.

True or False

1. In diffusion, particles move from an area of high to low concentration.

2. Diffusion does not require any additional energy to occur.

3. Small, charged or polar particles can move through the cell membrane by simple diffusion.

What if a cell needs large or charged/ polar molecules. Can they move across the membrane?

Yes!

Selectively Permeable Selectively Permeable MembraneMembrane

•The cell membrane “picks” what molecules can enter and exit the cell because proteins in the membrane allow specific macromolecules or ions in or out of the cell.

Facilitated diffusion

•Proteins help particles move across the membrane

•Transport proteins span the phospholipid bilayer, but allow only ___________ molecules through. >> Selectivity

specific

Types of transport proteins•____ __________ are non–polar

on the outside and polar on the inside. They provide a pore for ions and polar particles to move through.

Ion channels

•_________ _______________ bind to specific particles, carry them through the membrane, and release them on the other side.

http://www.stolaf.edu/people/giannini/flashanimat/transport/caryprot.swf

Carrier Proteins

Remember!

•In diffusion-particles (solutes) move from an area of HIGH concentration to LOW In osmosis- water moves from a HYPOTONIC environment to a HYPERTONIC environment

•Diffusion requires NO energy input• http://scienceguyinatie.blogspot.com/2008/11/cell-membrane-animation-of-word-wall.html

Simple vs. Facilitated• In simple diffusion, particles move

between phospholipid molecules of the membrane.

• In facilitated diffusion, particles move through transport proteins in the membrane.

•Both do NOT use energy. Particles must move down the concentration gradient.

But what if you needed to move particles against their concentration gradient?

Active TransportActive Transport

•Transport proteins use ________to move particles against their concentration gradient, from a low concentration to a high concentration.

energy

Sodium-Potassium Pump:

•Carrier- protein that pumps

3 sodium ions (Na+)________

the cell, while

pumping 2 potassium ions

(K+)________.

outside

inside

http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/ion_pump/ionpump.html

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html

1. 3 Na+ ions from inside the cell bind to the pump protein. Energy from ATP is added to the protein.

2. The Na+ ions are moved to the outside of the cell.

3. The 3 Na+ ions are released and 2 K+

ions bind to the protein.

4. The protein changes back and releases the 2 K+ ions into the cell.

Vesicle Mediated Transport

•The fluid plasma membrane can “pinch” off forming vesicles that can move very _______particles or lots of ______particles.

•This process needs _______.

largesmall

energy

Endocytosis•Outside materials are brought __________ the cell.

1) Food particle

3) Vesicle with food

2) Pouch forming around food

inside

Endocytosis

Phagocytosis• “Cell eating” • Cell engulfs large food particles and the

vesicle is a food vacuole.• http://www.stolaf.edu/people/giannini/flashanimat/cellstructures/phagocitosis.swf

Pinocytosis• “cell drinking”• Cell engulfs small droplets of surrounding

fluid.

Exocytosis•Material from inside the cell is

released _________ by vesicles.

1) Vesicle fuses with membrane

2) Pouch opens

3) Particle released

outside