Cell Boundaries Part 1

Cell BoundariesCell Boundaries

Chapter 7 Section 3Chapter 7 Section 3

What are boundaries?What are boundaries? We have borders We have borders

surrounding surrounding countriescountries

We have boundaries We have boundaries on a playing fieldon a playing field

Why are borders Why are borders important?important?

What are the borders of a What are the borders of a cell?cell?

Cell membraneCell membrane Thin, flexible barrierThin, flexible barrier

Cell wallCell wall Plant, algae, fungi, prokaryotesPlant, algae, fungi, prokaryotes Strong supporting layerStrong supporting layer

Cell MembraneCell Membrane What does it do for cell?What does it do for cell?

Controls what goes in and out Controls what goes in and out Regulates molecules moving from one liquid side of the Regulates molecules moving from one liquid side of the

cell to the other liquid side of the cellcell to the other liquid side of the cell

ProtectsProtects SupportsSupports

Cell MembraneCell Membrane Lipid bilayerLipid bilayer

What are lipids?What are lipids? What does bi- mean?What does bi- mean? What’s a layer?What’s a layer?

A cell membrane is made of twoA cell membrane is made of two

layers of lipid moleculeslayers of lipid molecules

Other things in the Other things in the membrane…membrane…

Proteins embedded Proteins embedded in lipid bilayerin lipid bilayer

Carbohydrates Carbohydrates attached to proteinsattached to proteins

So many different So many different molecules in molecules in membrane, we call it membrane, we call it a “mosaic” of a “mosaic” of different moleculesdifferent molecules

ProteinsProteins

Proteins help things Proteins help things get across get across membranemembrane

Kinda like a pumpKinda like a pump

Carbohydrates…Carbohydrates…

Chemical Chemical identification cardsidentification cards

““ID” card of cellID” card of cell Helps individual cells Helps individual cells

id each otherid each other

Cell WallsCell Walls

Outside cell membrane Outside cell membrane (does NOT replace (does NOT replace membrane!!!)membrane!!!)

Plants, algae, fungi, Plants, algae, fungi, prokaryotesprokaryotes

Have pores to allow Have pores to allow things inthings in

Function: SUPPORT and Function: SUPPORT and PROTECTPROTECT

Cell walls made of…Cell walls made of…

Protein and carbsProtein and carbs Plant cell walls made Plant cell walls made

up of CELLULOSEup of CELLULOSE This is a tough This is a tough

carbohydratecarbohydrate Wood and paperWood and paper

A biological membraneA biological membrane Cells exist in liquid environmentsCells exist in liquid environments Things need to get in and out of cellThings need to get in and out of cell Different ways to do this….Different ways to do this….

The Cell MembraneThe Cell Membrane

Concentration (conc.)Concentration (conc.) SolutionSolution

Mix of 2 or more substancesMix of 2 or more substances SolutesSolutes

Substance dissolved in solutionSubstance dissolved in solution Concentration is mass of SOLUTE in a given volume of Concentration is mass of SOLUTE in a given volume of

solution (g/L)solution (g/L) What is the concentration of 12 grams of salt dissolved in 3 What is the concentration of 12 grams of salt dissolved in 3

liters of water?liters of water? 12g/3L= 4g/L12g/3L= 4g/L

DiffusionDiffusion Particles constantly moveParticles constantly move Collide randomlyCollide randomly Spread out randomlySpread out randomly Diffusion is moving from area of HIGH conc. to Diffusion is moving from area of HIGH conc. to

area of LOW conc.area of LOW conc.

EquilibriumEquilibrium

When the conc. Of a When the conc. Of a system is the same system is the same throughout throughout

(same conc. on both (same conc. on both sides)sides)

What’s this have to do What’s this have to do with cells?with cells?

Cell have liquid inside and are found in liquid Cell have liquid inside and are found in liquid environmentenvironment

We have substances (solutes) inside and We have substances (solutes) inside and outside celloutside cell

Unequal concentrations means we get Unequal concentrations means we get DIFFUSION!!!DIFFUSION!!!

B/c diffusion depends on random particle B/c diffusion depends on random particle movements, substances diffuse across movements, substances diffuse across membranes membranes withoutwithout requiring the cell to use requiring the cell to use energyenergy