Cells must maintain homeostasis despite changes in their surroundings

How does the structure of the cell membrane relate to its job?

The membrane is only as good as its parts: phospholipid bilayer and proteins Phospho- portion is polar and

hydrophilic (attracts) -lipid portion is nonpolar and

hydrophobic (repels)

Fluid = ease of movementMosaic = made of…

Phospholipids (bilayer) Proteins embedded

▪ Channel proteins (door ways)▪ Marker proteins (cell identity)▪ Receptor proteins (on/off switch)

How do cells respond to changes in their environment?

Blue = water

Red = solute

Yellow = energy

Plus sign = Ion (like Na or K)

Block arrow = direction of molecule movement

High or low concentration solute

Have to maintain a constant internal environment (or homeostasis)

respond to the concentration gradient of the environment by moving molecules across membranes to either balance inside and outside concentrations (i.e. equilibrium) or to stockpile more

Tonicity is the concentration of dissolved solutes inside compared to outside the cell1.Determine the concentration of solutes found inside the cell2.Determine the concentration of solutes found outside the cell3.Compare the two – where is the concentration greater?4.Molecules move from high to low!

Concentration of dissolved solutes is equal to cell contents

Hyper = there is a higher solute concentration

Hypo = there is a low solute concentration

Passive TransportMolecules move from area of high concentration to low to establish equilibriumRequires no energy

Think of releasing helium balloons

Active TransportMolecules move from area of low concentration to high to stockpile materialsRequires energy

Think of catching them again

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

Click here for diffusion animated explanation

OsmosisWater moves from high to low in order to dilute a hypertonic environment

Click here for osmosis explanation

Facilitated diffusion

Diffusion of bigger molecules (but still smaller than particles) through channel proteinsClick here for facilitated diffusion explanation

Notice the sugar

molecules are too big

to pass through

the membrane but water

is not

Water moves equally in BOTH directions

Therefore, cell size does not change

* Note the cell is also isotonic compared to the solution around it

Water moves outside of the cell, toward higher solute concentration

Cell size shrinks* Note the cell is hypotonic compared to the solution around it

Water moves inside of cell, toward higher solute concentration

Cell size increases

* Note the cell is hypertonic compared to the solution around it

A cell in a hypo- environment will swell like a big fat hippo!

Click here for iso-hypo-hyper animation

There’s less turgor pressure

Pressure exerted on the walls of cell by water

Also called osmotic (water) pressure

Less = wilted

More = turgid

You will need: Fluid mosaic model coloring sheet & Ch 7 Study Guide

EQ: How do cells respond to changes in their environments?

Agenda: Review Active Transport notes (back of Fluid

Mosaic sheet) Check Ch 7 Study Guide

Ion pumpIons are stockpiled in an already highly concentrated area Click here for Sodium-potassium

pump animation

Endocytosis molecules too big to enter

through membrane are simply engulfed by cell

food is then packaged into vacuoles

cell “eating” (think PacMan) Aka Phagocytosis

Exocytosis Waste is expelled by cell

when vacuole combines with cell membrane

cell “pooping”

Be sure to also review earlier concepts in Chapter 7

Sort the terms or phrases presented on the following slides into the chart below:

Passive Transport

BothActive

Transport

Passive Transport

BothActive

Transport

Passive Transport

BothActive

Transport

Requires ATP

Passive Transport

BothActive

Transport

No energy required

Requires ATP

Passive Transport

BothActive

Transport

No energy required

Movement with the gradient

Requires ATP

Passive Transport

BothActive

Transport

No energy required

Movement with the gradient

Requires ATP

Movement against gradient

Passive Transport

BothActive

Transport

No energy required

Movement with the gradient

Requires ATP

Movement against gradient

Ion pump or endo/exocytos

is

Passive Transport

BothActive

TransportNo energy required

Movement with the gradient

Diffusion, osmosis, facilitate diffusion

Requires ATP

Movement against gradient

Ion pump or endo/exocytos

is

Passive Transport

BothActive

TransportNo energy required

Movement with the gradient

Diffusion, osmosis, facilitate diffusion

Movement through channel proteins

Requires ATP

Movement against gradient

Ion pump or endo/exocytos

is

Passive Transport

BothActive

TransportNo energy required

Movement with the gradient

Diffusion, osmosis, facilitate diffusion

Movement through channel proteins

Movement of small ions & molecules

Requires ATP

Movement against gradient

Ion pump or endo/exocytos

is

Passive Transport

BothActive

TransportNo energy required

Movement with the gradient

Diffusion, osmosis, facilitate diffusion

Movement through channel proteins

Movement of small ions & molecules

Requires ATP

Movement against gradient

Ion pump or endo/exocytos

is

Movement of large particles

Passive Transport

BothActive

TransportNo energy required

Movement with the gradient

Diffusion, osmosis, facilitate diffusion

Movement through channel proteins

Movement of small ions & molecules

Maintains homeostasis

Requires ATP

Movement against gradient

Ion pump or endo/exocytos

is

Movement of large particles

Passive Transport

BothActive

TransportNo energy required

Movement with the gradient

Diffusion, osmosis, facilitate diffusion

Maintains equilibrium

Movement through channel proteins

Movement of small ions & molecules

Maintains homeostasis

Requires ATP

Movement against gradient

Ion pump or endo/exocytos

is

Movement of large particles

Passive Transport

BothActive

Transport• No energy

required

• Movement with the gradient

• Diffusion, osmosis, facilitated diffusion

• Maintains equilibrium

• Movement through channel proteins

• Movement of small ions & molecules

• Maintains homeostasis

• Requires ATP

• Movement against gradient

• Ion pump or endo/exocytosis

• Movement of large particles

• Stockpiles materials (extra’s)

In the cell membrane model shown above, the molecules which move large molecules into and out of the cell are known as —

a)cholesterol. b)proteins. c)lipids. d)carbohydrates.

Penicillin works by destroying the bacteria’s cell wall. Therefore once the cell wall is destroyed osmosis can take place. The water moves into the organism and causes it to burst. If penicillin wasn’t there then the cell wall would prevent the bacterial cell from bursting.

1. Click here to access the Pearson “Diffusion and Osmosis” LabBench Activity

2. Complete concepts 1-53. Take lab quiz