Transcript CH 5 powerpoint

•
•
•
•
Homeostasis = internal balance
Transport = movement of materials
Wastes move out of the cell
Food and water move into the cell.
• Cells need to constantly moves
molecules across membrane to try to
reach equilibrium (equal balance).
Never truly reached.
Cell Membrane
• Phospholipid bilayer.
• Has Proteins embedded within it.
• Semi or Selectively Permeable (only certain
molecules are allowed to pass)
Terms you need to know..
• Solute = the substance BEING dissolved
– Sugar
– Salt
• Solvent = the liquid doing the dissolving
– water
(Solvent)
Passive Transport
• Movement of materials
WITHOUT energy (ATP)!
• Move from high
concentration to low
concentration
• Types of PASSIVE transport
• Diffusion
• Facilitated Diffusion
• Osmosis
Passive Transport moves..
•
•
•
•
Small molecules
Uncharged molecules (do not have a + or -)
Water
Gases
– Oxygen
– Carbon Dioxide
Passive Transport is like….
riding a bike down a hill, no energy is
needed.
So…does Passive Transport
require energy to move
molecules in or out of the cell?
•NO!
Diffusion
• Type of PASSIVE transport (no energy)
• Movement of molecules across the
membrane down the concentration gradient.
– High to a low concentration.
– “Spreading Out” of molecules
– Always trying to reach “equilibrium”
(molecules evenly spread out)
Rate of diffusion is driven by kinetic energy
~The more KE, the faster the rate of
diffusion
~Temperature (hot is faster than cold)
~Motion
Equilibrium
• Molecules are balanced equally inside and
outside of cell.
• The cell is always trying to reach/maintain
this! (since molecules are always in motion)
Osmosis
• Type of PASSIVE transport
(no energy)
• The diffusion of
WATER molecules across a
membrane.
• Movement of water from area
of high water concentration to
an area of low water
concentration.
• Always trying to reach
“equilibrium” (molecules
evenly spread out)
What causes the water to move?
• Concentration gradient of solutes
– A difference of solute concentration
between the inside and outside of a
cell
• “Solutes Suck”
– Water will move to the area with the greater
solute concentration
Diffusion of water
Example: Sugar and water.
Sugar = solute (being dissolved)
Water = solvent (doing the dissolving_
Based on the concept of osmosis, what would
you expect to happen in this setup?
A. No movement of water will occur.
B. Water will move in both directions equally.
C. The net movement of water will be from side B
to side A.
D. The net movement of water will be from side A
to side B.
SOLUTES
SUCK!!!!
Osmosis Notes
• Hypotonic solution – concentration of solutes is
greater inside the cell than outside.
– Water enters cell. Cell swells, gets bigger
• Isotonic solution – the concentration of solutes is the
same inside and outside of cell.
– Equal water moving in as out.
• Hypertonic solution – concentration of solutes is
greater outside the cell than inside.
– Water leaves cell. Cell shrinks, gets smaller
Hypo, Hyper, Isotonic…
Imagine that the membrane shown below is
impermeable to the solute molecules but
permeable to water. Which way will water
flow?
A. left to right
B. right to left
Examples!
Examples!
Facilitated Diffusion
• Type of PASSIVE transport
(no energy)
• Diffusion of a substance
across the membrane with
the help of a protein
embedded in a membrane.
• Movement is assisted
• Still moving molecules
from high to low
Active Transport
• REQUIRES ATP!!! (energy)
• Takes work from cell’s mitochondria
• Movement of molecules across the membrane
against (up) the concentration gradient
• From LOW to HIGH concentration
• Types of Active
• Pumps (proteins)
• Endocytosis
• Exocytosis
=
ENERGY
Active Transport moves…
• very LARGE molecules
• Charged molecules (ions)
– Na+
– K+
– Cl-
Movement
of squares
(low to
high
concentraion
)
Active
Transport is
like…
riding a bike up a hill,
ENERGY is required.
Types of Active Transport
Sodium Potassium (Ion) Pump
This is where the concentration is moving “low to high concentraion”
Uses proteins in membrane to “pump” ions against concentration gradient
Ions are elements with a charge ( + or - )
Exocytosis (type of active transport)
• Movement of large molecules
OUT of the cell
• Molecules surrounded by
bilayer vesicle (from Golgi)
• Membrane absorbs bilayer
vesicle (seals back up)
• Large molecules pushed out
Endocytosis (type of active transport)
large molecules INTO the cell.
Movement of
• Membrane starts to make a inward fold (dip)
• Large molecules move into that opening/pocket
• Membrane surrounds the molecules with bilayer (creating a
vesicle)
• Vesicle (molecules inside it) moves into the cell
• Membrane seals back up
Summary of
Passive vs. Active Transport
Passive
• NO energy
• High to Low
• Down the
concentration gradient
• Diffusion
• Osmosis
• Facilitated Diffusion
Active
• Requires energy
(ATP)
• Low to High
• Up the concentration
gradient
• Endocytosis
• Exocytosis
Summary of
Passive vs. Active Transport
Passive
•Can move….
•Small molecules
•Uncharged molecules
•Water
•Gases
– Carbon Dioxide
– Oxygen
Active
•Can move….
•LARGE molecules
•Charged molecules
(ions: Na+, K+, Cl-)
Summary of
Passive vs. Active Transport
• What do both types of cell transport have in
common (similarities)?
• Movement of molecules in/out of cell
membrane
• Trying to reach equilibrium
• Helps cell maintain homeostasis – stable
internal balance needed for the cell’s
survival