Review:
­
types of organelles
­
plants vs animals
­
prokaryotic vs eukaryotic
Oct 13­2:57 PM
How does a Cell Compare to a City?
­
food supply
­
waste removal
­
water supply
­
transfer of information
Oct 13­2:59 PM
1
The Cell Membrane
­
the membrane is expected to do a number of things
1. transport raw materials into the cell
2. transport manufactured products and waste out of the cell
3. prevent the entry of unwanted matter into the cell
4. prevent the escape of the matter needed to perform the cellular functions
HOW DOES IT DO THIS???
Oct 13­3:00 PM
Cellular Processes:
Homeostasis
­
conditions inside the cell must remain constant for it to perform its life functions
­
the maintaining of these conditions is called homeostasis
­
the cell membrane is selectively permeable (allows only certain things in) which helps maintain homeostasis
­
in the case of multicellular organisms every cell is bathed in extracellular fluid which plays a role in cellular processes
Oct 13­3:09 PM
2
Cell in Extracellular Fluid
Cell
Material moves in
and out which
maintains
homeostasis
Extracellular Fluid
Blood
Oct 14­7:53 AM
Diffusion
­
the movement of molecules from a region of high concentration to a region of low concentration
­
these molecules include nutrients such as oxygen and waste such as carbon dioxide
­
diffusion will continue until there are equal amounts of a material throughout an area (equilibrium)
Oct 14­7:59 AM
3
­
diffusion requires no energy because it moves materials with the concentration gradient
High Concentration
Dif
fus
ion
Concentration
Gradient
­
Low Concentration
diffusion also moves molecules within a cell but the rate is lower due to a smaller concentration gradient
Oct 14­8:50 AM
­
diffusion will not remove all material from a cell because it only goes until equilibrium
­
because it requires no energy diffusion is known as a passive transport method
Oct 14­8:54 AM
4
Osmosis
­
a cell membrane is only capable of diffusing small molecules such as oxygen and carbon dioxide
­
water is larger so it has to be moved in by osmosis
­
osmosis is the diffusion of water across a semi­permeable membrane from a region of high concentration to an area of low concentration
­
follows a concentration gradient and requires no energy (passive transport)
Oct 14­9:47 AM
­ osmosis exists as three conditons
1. Isotonic Conditions
­
when the water concentration inside the cell equals the water concentration outside the cell
­ thus there is no net movement of water (this is the preferred condition of animal cells
Animal Cell
Plant Cell
Oct 14­9:50 AM
5
2. Hypotonic Conditions
­
when the water concentration outside the cell is greater then inside the cell
­
thus there is a net movement of water into the cell
­
in animal cells this may result in the cell membrane bursting, but in a plant cell the cell wall prevents this from happening
­
hypotonic is the preferred condition of plant cells because it helps a plant maintain its rigidity
Oct 14­9:56 AM
Animal Cell
Plant Cell
Excess water moves
in and animal cell may burst
Excess water moves
in but cell wall prevents
bursting
Oct 14­10:04 AM
6
3. Hypertonic Conditions
­
when the water concentration inside the cell is greater then the concentration outside the cell
­
thus water moves out of the cell
Animal Cell
Plant Cell
­water leaves the cell
which then shrivels
­water leaves the cell
and cytoplasm shrinks inside the cell wall
Short Osmosis Video
Oct 14­10:07 AM
See page 55, figure 2.26
Oct 14­10:10 AM
7
Facilitated Diffusion
­
some molecules cannot pass through the cell membrane themselves (Ex. glucose)
­
a carrier protein may be required to move some material into and out of the cell
­
carrier proteins can only move one specific substance, nothing else
­
once joined with the carrier protein the substance will still move from high concentration to low concentration (still passive transport)
( See fig. 2.27, pg 57 and fig. 2.28, pg 58)
Facilitated Diffusion Link
Oct 16­7:54 AM
Oct 19­12:59 PM
8
Readings:
­
page 50 ­ 58
Questions:
­
page 61, #'s 1,6,7,8,9,10,11,13,14
Oct 16­7:59 AM
9