Transcript 2nd Presentation

Cell Transport
Central Questions
• What is responsible for transport in and out of the
cell?
• What are the characteristics of the cell membrane?
• What are the two types of transport?
• What are the two types of passive transport and how
do they work?
Why do we need cell transport?
• Biochemistry requires materials like water, oxygen and
food to be brought into the cell
• Afterwards, products such as CO2, excess water and
waste must be removed
• Proper flow into and out of the cell is essential in
maintaining homeostasis (keeping the conditions
inside the cell the same)
Remember...
What cell part is responsible for this function?
A. Cell wall
B. Cell membrane
C. Nucleus
D. ER
Cell Membrane
• Phospholipid bilayer
o Phospholipid—lipids with phosphate attached
o Bilayer—two layers of phospholipids
• The phospholipids have a phosphate ‘head’ structure
and 2 lipid ‘tails’
• Proteins are placed throughout to create passageways
and others are for cell identification
Heads like water—hydrophilic (love water)
Tails hate it—hydrophobic (scared of water)
I’m happy because I
water
I’m scared
Now we’re safe!
We’re still happy!
Fluid-Mosaic Model
• This is called fluid-mosaic because it is fluid (made of oils)
and mosaic (made of many parts, phospholipids and
proteins)
Getting Through the Membrane
• The membrane is semi-permeable and only
allows some substances in or out. Water and
teeny weeny stuff can get through the
membrane.
• Large compounds like proteins and sugars need
to go through protein channels.
Types of Transport
• Passive transport
-Moves materials across the cell membrane without using
energy.
-From high concentration to low concentration
• Active transport
-From low concentration to high concentration
-Uses energy to move things in and out
Protein Channels
For two purposes:
a. Facilitated Diffusion—channel acts as a door so
larger compounds can move as diffusion would
normally (passive)
b. Protein Pumps—proteins pump molecules against
the concentration gradient (active)
Solutions
• Two parts of a solution: solute is the ‘stuff’ being dissolved; solvent is
what it’s dissolved in
• Nature makes molecules move from high to low until equilibrium
(equal concentration) is reached.
• That’s why passive transport uses no energy!
• Water is the ‘universal solvent’
Types of Solutions
• There are three types of solutions a cell can be in:
1. Hypertonic—solute concentration is HIGHER OUTSIDE the
cell
2. Hypotonic—solute concentration is LOWER OUTSIDE the
cell
3. Isotonic—same inside and outside. When there is a
difference in the concentration inside and outside, we call
it a concentration gradient
Passive Transport
• Two types:
a. Diffusion—solute does the moving (from high to low
concentration)
b. Osmosis—water does the moving (from high to low
concentration)
Diffusion is pretty straightforward, the solute will move in or
out of the cell to the lower concentration.
Osmosis
Osmosis is most noticeable if diffusion
is blocked.
• In hypotonic solution, water movies
in and the cell swells up
-Hypo sounds like Hippo…a fat animal
• In hypertonic solutions, water moves
out and the cell shrivels
• -Hyper people are skinny
Active Transport
• Remember that movement from low to high
concentration takes energy. There are a few ways cells
can do this:
• Protein channels: some protein channels can use
energy to pump materials against the concentration
gradient
• Bulk transport: moves thing too large to fit through
protein channels
Bulk Transport
• Endocytosis—wraps around something large to
bring it in ‘pacman style’
• Exocytosis—cell pushes something large out
wrapped in membrane
• Phagocytosis—moves solids
• Pinocytosis—moves liquids
Central Questions
• What is responsible for transport in and out of the
cell?
• What are the characteristics of the cell membrane?
• What are the two types of transport?
• What are the two types of passive transport and how
do they work?