Download Goal 2.03 Cell Processes

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2006-2007
Homeostasis
Maintaining a balance of conditions within the cell
(or organism).
• maintaining pH (cells need pH of 6.8-7.2)
pH Scale
Acid
Neutral
Base
1 2 3 4 5 6 7 8 9 10 11 12 13 14
most cells
Lab: pH and Buffers
pH = potential hydrogen (meaning the ability of a
solution to attract hydrogen ions)
Acidic solution
H+
H+
Basic solution
OH-
H+
H+
OHOH-
OHH+
OH-
Buffers and pH Virtual Activity
http://www.mhhe.com/physsci/chemistry/essenti
alchemistry/flash/buffer12.swf
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
High metabolism
uses energy
FAST
Low metabolism
uses energy
SLOWLY
Homeostasis (cont.)
Maintaining a balance of conditions within the cell
(or organism).
maintaining
blood sugar
levels
Person eats food
containing
glucose
Blood sugar
levels lower
Blood sugar levels rise
FEEDBACK:
Insulin is released to control
the incoming glucose and
maintain blood sugar levels
HSW: Simply Science: Equilibrium
Diffusion
SuperQuick Demo: Colored water into water.
 Move from HIGH to LOW concentration
 passive transport
 no energy needed
Low
Concentration
High
Concentration
diffusion
Concentration Gradient
Higher concentration
Na+
H2O(sodium)
(water)
of molecules.
Lower concentration
of molecules.
Molecules move from high to low
 Diffusion (substances move)
 move from HIGH to LOW concentration
across the concentration gradient.
Concentration
gradient
Membrane
High
Low
Cell Homeostasis
 Remember that the
 cell membrane controls what enters
and leaves the cell
IN
OUT
food
- sugars
- proteins
- fats
salts
O2
H2O
waste
- ammonia
- salts
- CO2
- H2O
products
- proteins
Cell needs materials in & products or waste out
Remember…
 Membrane is made of special kind of lipid
 phospholipids
“attracted to water”
 “split personality”
 Membrane is a double layer
 phospholipid bilayer
phosphate
inside cell
lipid
outside cell
“repelled by water”
Semi-permeable membrane
 Cell membrane controls what gets in or out
 Need to allow some materials — but not all — to
pass through the membrane
 semi-permeable (semi – partly)
 only some materials can get in or out
So what needs to get across the membrane?
sugar lipids
aa
O2
H 2O
salt
waste
Crossing the cell membrane
 What molecules can get through the cell
membrane without doors or help?
 fats and oils can pass directly through
inside cell
waste
outside cell
lipid
salt
sugar aa
H 2O
but…
what about
other stuff?
Cell membrane protein channels
 Need 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
waste
salt
H 2O
aa
sugar
outside cell
 Channels are made of proteins
 proteins both “like” water & “like” lipids
bi-lipid
membrane
protein channels
in bi-lipid membrane
Protein channels (cont.)
 Proteins act as open doors in the membrane
Concentration gradient
 channels to move specific molecules through cell membrane
HIGH
LOW
Sugar molecules
Movement through the channel
 Why do molecules move through the membrane if
they find a channel?
HIGH
?
LOW
?
Simple Diffusion
 Move from HIGH to LOW
fat
inside cell
LOW
fat
fat
fat
fat
fat
Which way
will these fat
molecules
move?
HIGH
outside cell
fat
fat
fat
fat
fat
fat
fat
fat
Facilitated Diffusion
 Move from HIGH to LOW through a channel
sugar sugar
sugar
sugar
inside cell sugar
sugar
LOW
Which way will
sugar move?
HIGH
outside cell
sugar
sugar sugar
sugar
sugar
sugar
sugar
Simple vs. facilitated diffusion
simple diffusion
inside cell
lipid
facilitated diffusion
LOW
inside cell
H 2O
protein channel
outside cell
outside cell
HIGH
H 2O
Active transport
 Cells may need to move molecules
against concentration gradient
 need to pump “uphill”

from LOW to HIGH using energy
 protein PUMP
 Requires ATP
Notice the direction
of Amino Acid
movement and the
concentrations!
Na+ activates the
pump.
Low
ATP
High
Quick Review…
simple
diffusion
facilitated
diffusion
active
transport
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
Osmosis
 Water is so important that we discuss it separately
 Osmosis
 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 cell
 Cells in Freshwater
 a cell in fresh water
 high 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 water
 Contractile vacuole in Paramecium
 Cells in Saltwater
 a cell in salt water
 low concentration of water around
cell

cell loses water
 example: shellfish
 problem: cell loses water


plasmolysis in plants
shrinking cell
 solution: take up water
Hypertonic
 Cells in Balanced
conditions
 no difference in concentration of
water between cell &
environment



cell in equilibrium
example: blood
problem: none


water flows across membrane
equally,
in both directions
volume of cell doesn’t change
Isotonic
BLOOD!
Animated Cell Responses to Solution Concentrations:
http://www.phschool.com/science/biology_place/labbench/lab1/watpot.html
Learning through Osmosis?
Hands-On w/Virtual Lab 3: Diffusion of IKI through
Selectively Permeable Membrane
Virtual Lab 4: Osmosis thru a Selectively Permeable Membrane
Virtual Lab 5: Onion Cell Plasmolysis
DO NOT
TOUCH
LAB
ITEMS!
Cells need ENERGY to power biochemical reactions.
How does a biochemical reaction work?
Reactant
Reactants
ENTER the
reaction.
Endo – inside
Exo – outside
Reactant
Energy is
absorbed or
released by
the reaction.
Products are
PRODUCED by
the reaction.
EXOthermic Reaction = RELEASES energy
Reactant
Reactant
Reactants
ENTER the
reaction.
EXOTHERMIC
Products are
PRODUCED by
the reaction.
ENDOthermic Reaction = ABSORBS energy
Reactant
Reactant
Reactants
ENTER the
reaction.
ENDOTHERMIC
Energy is
ABSORBED by
the reaction.
Products are
PRODUCED by
the reaction.
Exothermic Reaction = Releases Energy
ACTIVATION ENERGY = energy required
ENERGY
to cause the reaction to occur.
Energy
RELEASED
TIME
Endothermic Reaction = Absorbs Energy
ACTIVATION ENERGY = energy required
ENERGY
to cause the reaction to occur.
Energy
ABSORBED
TIME
Any Questions?