Cell Membrane

Movement of Substances Into and Out of the Cell

Created by Mr. Woodbury & Mrs. BeddesModified by Mrs. Slater

Cell Membrane Structure

Cells are surrounded by a thin, flexible, selectively permeable membrane.

Selective PermeabilityAllows only certain substances to pass

through

Fluid Mosaic ModelThe membrane is

fluid because it is not rigid or fixed like a wall Fluid in the verb-

sense… http://www.youtube.com/watch?v=SpPXewlgmcw

The parts shuffle, move and flex

The membrane is like a mosaic with the different parts put together Different parts

have different shapes and functions

5

PhospholipidsA phospholipid is

made of a 1 polar, hydrophilic head and 2 non-polar hydrophobic tails Classified as a

lipid The main part of

membranes

Cell Membrane Structure

Phospholipid bilayer Arranged with hydrophilic head on outside and hydrophobic tails

on inside

DefinitionsHydrophilic head

Hydro- ≈ water -philic ≈ loving Polar regions of a molecule that are

attracted to water

Hydrophobic tails Hydro- ≈ water -phobic ≈ afraid or hating Nonpolar regions of a molecule that avoid

water or prefer other hydrophobic parts fatty acid tails

Cell Membrane Structure

Proteins Enzyme activity, cell-to-cell recognition, cell signaling, transport

Cell Membrane Structure

Cholesterol Helps to stabilize membrane

10

11

Selectively Permeable Cell Membrane DrawingDraw and label the parts of a cell

membrane include phospholipids, proteins, and cholesterol

Draw and label the hydrophobic regions & the hydrophilic regions

Describe/explain each part of the cell What do phospholipids, proteins, and

cholesterol do? What does hydrophobic & hydrophilic mean?

12

Membranes in organellesYou will be given one of the following

organelles to draw. Since these are all made of membranes,

you must draw a large portion of the membrane as the phospholipid bilayer If it has an outer layer that is made of a

membrane, you must draw that as a phospholipid bilayer

13

14

Cell Membrane Processes

Cell Transport

15

Cell Membrane Illustration We will add in the different parts and

processes of the cell membrane to this drawing as we go.

First section: the phospholipid bilayer. Two layers of phospholipids Hydrophilic heads pointing out and in Hydrophobic tails pointing towards each

other.

16

17

Methods of TransportTransport of materials in and out of the

cell falls into two categories Passive transport Active transport

Which one sounds like it requires energy?

http://www.youtube.com/watch?v=j5Qway4LAkk&feature=related

18

Membrane Proteins

19

Passive TransportDoes not require energy from the cellType 1: Diffusion

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

Stuff goes from where it is to where it isn’t Happens because of random movement of

particles Examples: Oxygen, carbon dioxide, some

water, and lipid-soluble substances (non-polar molecules)

20

O2

CO2

21

Diffusion… High to LowTo determine which direction material will

go, you must know the amounts/ratios/percentages of materials in the different areas.

Water coloring example Coloring first went to bottom (high

concentration) Then slowly diffused through water (low

concentration) High to low = passive transport

22

A Special Condition Equilibrium

Number of molecules moving in one direction is equal to the number moving in the other direction

The random motion and collisions are still happening

The net movement in all directions equals out.

23

Passive Transport, cont.Type 2: Facilitated diffusion

Transport proteins allow the diffusion of certain substances

Channels, tunnels, sometimes with gates Gates may open & close due to changes in

conditions. Examples: Water, ions and sugars

24

Facilitated Diffusion

25

O2

CO2

26

Passive Transport, cont. Type 3: Osmosis: Passive transport of

water across a membrane Hypertonic

Solution with a higher solute concentration Water leaves the cell to dilute the external solution

Isotonic Solution with an equal solute concentration No net movement of water (water enters and leaves the

cell at the same rate = equilibrium) Hypotonic

Solution with a lower solute concentration Water enters the cell to dilute the internal solution

27

Transport Across a MembraneVideo footage:

http://www.linkpublishing.com/video-transport.htm

How cells behave...

29

Tonicity Flip Diagram Fold a piece of paper in half hot dog-style Fold in thirds. Label & draw 1 for each

section: Hypertonic Solution

Inside of the cell: 10% NaCl & 90% water Outside of the cell (the environment):

15% NaCl & 85% water Isotonic Solution

Inside of the cell: 10% NaCl & 90% water Outside of the cell (the environment):

10% NaCl & 90% water Hypotonic Solution

Inside of the cell: 6% NaCl & 94% water Outside of the cell (the environment):

3% NaCl & 97% water

30

Flip Diagram – Hypertonic "HYPER" means more than.The concentration of solute (salt)

outside the cell is greater than that of the solution outside the cell, so water will move out of the cell. Plant cells lose water and start to wilt. Animal cells will shrink / shrivel. In both cases, the cell may die. Overall, the cell size will decrease.

31

Flip Diagram – Isotonic "ISO" means equal to. If the concentration of solute (salt) is equal

on both sides of the cell membrane, the water will move into the cell, but it won't change the overall amount of water on either side. Humans need isotonic solutions to be at equilibrium which occurs when equal amounts of water are entering and exiting the cell. Overall, the cell size will not change.

32

Flip Diagram – Hypotonic "HYPO" means less than. The concentration of solute (salt) inside the

cell is greater than that of the solution outside the cell, so water will move inside of the cell. The cell will _____________ water and grow ____________. In plant cells, the central vacuoles will fill and the plant becomes stiff and rigid. In animal cells, the cell may be in danger of ________________. Overall, the cell size will ___________.

Active Transport Requires energy from the cell

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

Goes “uphill” Type 1: Pumps

Particle binds to a transport protein Protein changes shape which requires

energy Releases particle inside the cell Protein returns to original shape

34

The Sodium-Potassium Pump

35

O2

CO2

Active Transport, cont.Movement of large particles, using

membrane movement/reconfigurationType 2: Endocytosis

“Inside + cell + process” Cell surrounds and takes in material from its

environment Often used for nutrients or foreign invaders

Type 3: Exocytosis “Outside + cell + process” Reverse process of endocytosis Used to expel wastes and secrete

substances produced by the cell

Endocytosis

Exocytosis

38

Endocytosis & Exocytosishttp://www.youtube.com/watch?

v=1w10R9lv7eQ

39

O2

CO2

40

Basic types of transport

41

A Summary

42

Membrane Transport AnimationAnd once again, so you understand what

she’s talking about…

http://www.youtube.com/watch?v=j5Qway4LAkk&feature=related

43

Vocab TermsPassive TransportActive TransportDiffusionEquilibriumFacilitated Diffusion

OsmosisHypertonicIsotonicHypotonicEndocytosisExocytosis

For the lab Compare the internal environment of the

egg/cell to the liquid it is soaking in. Interior of cell = water + solutes (stuff) Exterior of cell = corn syrup or pure water Which exterior liquid has a higher

percentage of water? Which exterior liquid has a higher

percentage of stuff? Which one was hypertonic? Which one was hypotonic? Is your mystery solution hyper-, hypo-, or

isotonic?