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?