7.2 PLASMA MEMBRANE

7.2 THE PLASMA MEMBRANE

WHAT YOU WILL LEARN: -how a cell’s plasma membrane functions -the roles of proteins, carbohydrates &

cholesterol in the plasma membrane

READING QUESTIONS1-HIGHLIGHT the items in the figure that

enter the cell thru pm/CIRCLE those that exit the cell

oxygen

glucose

water

READING QUESTIONS2-EXPLAIN the purpose of phospholipid

bilayer?-allows plasma membrane to survive & function in its watery environment

READING QUESTIONS3-IDENTIFY: CIRCLE one phospholipid—

LABEL its head/tail

headtail

READING QUESTIONS4-DEFINE the role of transport proteins

5-NAME 3 substances that move among the phospholipids of the PM

-move substances through plasma membrane

-proteins/carbohydrates/cholesterol

• http://www.dnatube.com/video/360/Fluid-Mosaic-Model

• http://www.susanahalpine.com/anim/Life/memb.htm

REVIEW -homeostasis:-maintain balance / internal environment

7.2 THE PLASMA MEMBRANE

http://www.dnatube.com/video/360/Fluid-Mosaic-Model

selective permeability-- -CONTROLS substances ENTER / LEAVE (homeostasis)

WHAT WHEN HOW *cells must keep proper concentration of nutrients / water / expel

waste

-some molecules can cross the plasma membrane --(water)-others must go through channels --(Na, Ca, etc)

This is like a FISH NET--HOW?T/P/S: analogy for a cell’s selective permeability

FUNCTION of the PLASMA MEMBRANE

FUNCTION of the PLASMA MEMBRANEFUNCTION of PLASMA MEMBRANE-boundary separates cell & environment -allows water, nutrients & oxygen into

cell -allows waste & CO2 out of cellOUTSIDE CELL

INSIDE CELL

NUTRIENTSOXYGEN

WASTE

CARBON DIOXIDE

WATER

polar head— hydrophilic …likes water

non-polar tail—hydrophobic …repels water

STRUCTURE of PLASMA MEMBRANE

STRUCTURE of PLASMA MEMBRANE

A- carbohydrate chain

B- transport protein

C- polar heads

D- non-polar tails

E-cholesterol

STRUCTURE of PLASMA MEMBRANE

B- lipids C- phospholipid A- transport protein F- phospholipid bilayer D- fluid mosaic model E- selective permeability

STRUCTURE of PLASMA MEMBRANE

FUNCTION of the PLASMA MEMBRANEDESCRIPTION SELECTIVE

PERMEABILITY

HOMEOSTATSIS

PLASMA MEMBRANE

1-The process of maintaining balance inside a cell.2-A boundary between a cell & its environment.3-Feature of plasma membrane that keeps some substances out.4-Separates prokaryotic & eukaryotic cells from the watery environment in which they exist5-The quality of a plasma membrane that allows oxygen & glucose to move in6-Maintained by the plasma membrane

-polar headsbarrier to water environment in/out of cell

-non-polar tailsprevent substances dissolve in water from passing thru PM

-carbohydrate chainidentify chemical signals from environment

-cholesterolprevent tails from sticking together, keep membrane fluid

-transport proteinlike tunnels--move materials thru plasma membrane

-membrane proteinreceptors—on outside, send signals to inside of cellanchors—on inside, hold membrane to cell’s internal shape

STRUCTURE of PLASMA MEMBRANE

EXPLAIN/DRAW

1-MEMBRANE PROTEIN -create tunnels -PASSIVE

2-TRANSPORT PROTEIN -create tunnels -”pump” substances / ACTIVE

STRUCTURE of PLASMA MEMBRANE

EXPLAIN/DRAW

CHOLESTEROL -non polar -keeps PM fluid--prevents fatty acid tails from sticking -maintains homeostasis in cell

CARBOHYDRATE CHAIN -help cell identify chemical signals from environment

STRUCTURE of PLASMA MEMBRANE

21

FLUID MOSAIC MODEL

This “MODEL” for the structure of the membrane is called the:

FLUID MOSAIC MODELFLUID-individual phospholipids / proteins move freely within the

layer-- like a liquidMOSAIC-“pattern” produced by the scattered protein molecules

AS Biology. Foundation. Cell membranes and Transport 22

Cell Membranes from Opposing Neurons (TEM x436,740).

} cell membrane

7nm wideCell membrane {

Nerve cell

Nerve cell

Gap between cells