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? Glycoprotein Protein Cholesterol Phospholipids Outside Cell (Extracellular Matrix) Inside Cell (Cytoplasm)

The Plasma Membrane Glycoprotein Protein Cholesterol Phospholipids Outside Cell (Extracellular Matrix) Inside Cell (Cytoplasm)

The Plasma Membrane Glycoprotein Protein Cholesterol Phospholipids 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 amount area

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 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 HypotonicIn 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 InSwells, then bursts (cytolysis) Swells, increases turgor pressure Hypertonic Isotonic

Environment outside cell Water moves… Effect on ANIMAL cell Effect on PLANT cell Hypotonic InSwells, then bursts (cytolysis) Swells, increases turgor pressure HypertonicOut Isotonic

Environment outside cell Water moves… Effect on ANIMAL cell Effect on PLANT cell Hypotonic InSwells, then bursts (cytolysis) Swells, increases turgor pressure HypertonicoutShrinks (crenation) Isotonic

Environment outside cell Water moves… Effect on ANIMAL cell Effect on PLANT cell Hypotonic InSwells, then bursts (cytolysis) Swells, increases turgor pressure HypertonicoutShrinks (crenation) Shrink (plasmolysis) Isotonic

Environment outside cell Water moves… Effect on ANIMAL cell Effect on PLANT cell HypotonicInSwells, then bursts (cytolysis) Swells, increased turgor pressure HypertonicOutShrinks (crenation) Shrinks, (plasmolysis) Isotonic

Environment outside cell Water moves… Effect on ANIMAL cell Effect on PLANT cell Hypotonic InSwells, then bursts (cytolysis) Swells, increases turgor pressure HypertonicoutShrinks (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 InSwells, then bursts (cytolysis) Swells, increases turgor pressure HypertonicoutShrinks (crenation) Shrink (plasmolysis) IsotonicIn and out at the same rate

Environment outside cell Water moves… Effect on ANIMAL cell Effect on PLANT cell Hypotonic InSwells, then bursts (cytolysis) Swells, increases turgor pressure HypertonicoutShrinks (crenation) Shrink (plasmolysis) IsotonicIn and out at the same rate Stays the same

Environment outside cell Water moves… Effect on ANIMAL cell Effect on PLANT cell Hypotonic InSwells, then bursts (cytolysis) Swells, increases turgor pressure HypertonicoutShrinks (crenation) Shrink (plasmolysis) IsotonicIn and out at the same rate 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 Membrane 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. 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

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 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

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 _______. large small 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. 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