2006-2007

http://www.simpletruths.tv/store/movies.php?movie=race

Homeostasis Maintaining a balance of conditions within the cell (or organism).

• maintaining pH (cells need pH of 6.8-7.2)

Neutral

pH ScalepH Scale

AcidAcid Base

1 2 3 4 5 6 7 8 9 10 11 12 13 14

most cellsmost cells

Lemon juice Soap

Vinegar Hydrogen peroxide

Lab: pH and Buffers

pH = potential hydrogen (meaning the ability of a solution to attract hydrogen ions)

Buffers and pH Virtual Activityhttp://www.mhhe.com/physsci/chemistry/

essentialchemistry/flash/buffer12.swf

H+

H+

H+

H+

H+

OH-

OH-

OH-

OH-

OH-

Acidic solution Basic solution

Homeostasis

Maintaining a balance of conditions within the cell (or organism).

• maintaining temperatures (humans 98.6oF) – shiver/sweat• metabolism = sum total of the body’s chemical activities

Metabolic Rate:

how fast an organism

uses up its stored energy.

High metabolismuses energy FAST

Low metabolismuses energy

SLOWLY

Homeostasis (cont.)

Maintaining a balance of conditions within the cell (or organism).

maintaining blood sugar levels

HSW: Simply Science: Equilibrium

DiffusionMove from HIGH to LOW concentration

passive transportno energy needed

diffusion

SuperQuick Demo: Colored water into water.

HighConcentration

LowConcentration

H2O (water)Na+ (sodium)Higher concentration of molecules.

Lower concentration of molecules.

Molecules will always go from high to low.

Concentration Gradient

Molecules move from high to lowDiffusion (substances move)

move from HIGH to LOW concentration across the concentration gradient.

Membrane

High

Low

Co

nce

ntr

atio

n

gra

die

nt

Cell HomeostasisRemember that the

cell membrane controls what enters and leaves the cell

INfood- sugars- proteins- fats

saltsO2

H2O

OUTwaste- ammonia- salts- CO2

- H2O products- proteins

Cell needs materials in & products or waste out

Remember…Membrane is made of special kind of lipid

phospholipids“split personality”

Membrane is a double layer phospholipid bilayer

inside cell

outside cell

lipid

“repelled by water”

“attracted to water”

phosphate

Semi-permeable membraneCell membrane controls what gets in or

outNeed to allow some materials — but not

all — to pass through the membrane semi-permeable (semi – partly)

only some materials can get in or out

aa H2Osugar lipids salt waste

So what needs to get across the membrane?

O2

Crossing the cell membraneWhat molecules can get through the cell

membrane without doors or help?fats and oils can pass directly through

inside cell

outside cell

lipid

salt

aa H2Osugar

waste

but…what about other stuff?

Cell membrane protein channelsNeed to make “doors” through membrane

protein channels allow substances in & out specific channels allow specific material in & out H2O channel, salt channel, sugar channel, etc.

inside cell

outside cellwaste salt

H2O aa sugar

Channels are made of proteinsproteins both “like” water & “like” lipids

bi-lipidmembrane

protein channelsin bi-lipid membrane

Protein channels (cont.)Proteins act as open doors in the

membranechannels to move specific molecules through cell

membrane

HIGH

LOWCo

nc

entr

ati

on

gra

die

nt

Sugar molecules

Movement through the channelWhy do molecules move through the

membrane if they find a channel?

?

?

HIGH

LOW

Simple Diffusion Move from HIGH to LOW

inside cell

outside cell

Which way will these fat molecules move?fat

fat

fat

fat

fat

fat fat

fatfat

fat

fat

fat

fat

fat

LOW

HIGH

Facilitated DiffusionMove from HIGH to LOW through a channel

inside cell

outside cell

sugar

sugar

sugar

sugar

sugarsugar

sugar sugar

sugarsugarsugar

Which way will sugar move?

sugarsugar

LOW

HIGH

Simple vs. facilitated diffusion

inside cell

outside cell

lipidinside cell

outside cell

H2O

simple diffusion facilitated diffusion

H2O

protein channel

HIGH

LOW

Active transport

Cells may need to move molecules against concentration gradient need to pump “uphill”

from LOW to HIGH using energyprotein PUMPRequires ATP

Low High

Notice the direction of Amino Acid movement and the concentrations!Na+ activates the pump.

ATP

Quick Review…simplediffusion

facilitateddiffusion

activetransport

ATP

When Surface Area Counts: Intestinal Folds increase the surface area through which substances can pass.

Villi = folds in the intestine that allow for more absorption area.

What is the purpose of folds in the intestinal lining?

Osmosis

Osmosis and the Egg Demonstration

OsmosisWater is so important that we discuss it

separatelyOsmosis

diffusion of water from high concentration of WATER to low concentration of water

across a semi-permeable membrane

Osmosis diffusion of water from high

concentration of WATER to low concentration of water across a semi-permeable membrane

High Low

Keeping water balance (Homeostasis)Cell survival depends on balancing

water uptake & water loss

freshwater balanced saltwater

Keeping right amount of water in cellCells in Freshwater

a cell in fresh waterhigh concentration of water

around cell cell gains water example: Paramecium problem: cells gain water,

swell & can burst water continually enters

Paramecium cell solution: contractile vacuole

pumps water out of cell

Hypotonic

Controlling waterContractile vacuole in Paramecium

Cells in Saltwater a cell in salt waterlow concentration of water

around cell cell loses water

example: shellfishproblem: cell loses water

plasmolysis in plants shrinking cell

solution: take up water

Hypertonic

Cells in Balanced conditionsno difference in

concentration of water between cell & environmentcell in equilibriumexample: bloodproblem: none

water flows across membrane equally, in both directions

volume of cell doesn’t change

Isotonic

BLO

OD

!

Animated Cell Responses to Solution Concentrations: http://www.phschool.com/science/biology_place/labbench/lab1/watpot.html

Learning through Osmosis?

Virtual Lab 4: Osmosis thru a Selectively Permeable Membrane

Virtual Lab 5: Onion Cell Plasmolysis

Hands-On w/Virtual Lab 3: Diffusion of IKI through Selectively Permeable Membrane

DO NOT TOUCH

LAB ITEMS!

Cells need ENERGY to power biochemical reactions.

How does a biochemical reaction work?

Product

Prod

uct

Prod

uct

Produc

t

Product

Reactant

ReactantReactant

Reactants ENTER the reaction.

Products are PRODUCED by the reaction.

Energy is absorbed or released by

the reaction.

Endo – insideExo – outside

EXOTHERMIC

Product

Prod

uct

Prod

uct

Produc

t

Product

Reactant

ReactantReactant

Reactants ENTER the reaction.

Products are PRODUCED by the reaction.

Energy is RELEASED by

the reaction.

EXOthermic Reaction = RELEASES energy

EXOthermic Reaction = RELEASES energy

Product

Prod

uct

Prod

uct

Produc

t

Product

Reactant

ReactantReactant

Reactants ENTER the reaction.

Products are PRODUCED by the reaction.

Energy is ABSORBED by the reaction.

ENDOthermic Reaction = ABSORBS energy

ENDOthermic Reaction = ABSORBS energy

ENDOTHERMICENDOTHERMIC

ENER

GY

TIME

Exothermic Reaction = Releases Energy

ACTIVATION ENERGY = energy required to cause the reaction to occur.

Energy

RELEASED

ENER

GY

TIME

Endothermic Reaction = Absorbs Energy

ACTIVATION ENERGY = energy required to cause the reaction to occur.

Energy

ABSORBED

Any Questions?