Transcript Carrier Proteins

Cellular Transport
Active vs. Passive
Cellular Transport Essential
Question.
• How and why is the plasma membrane
(structure & function) essential in maintaining
the homeostasis for the cell in reference to
transport, hypertonic solutions, hypotonic
solutions, and isotonic solutions?
Activating Strategy!
Scenario
Strawberries with
sugar.
Raisins in water.
Predict the
Outcome
Observed
Outcome
Plasma/Cell Membrane
• Surrounds and contains the cell’s contents
• Controls what enters or leaves the cell
• Double layer of phospholipids & proteins
Lipids of Cell Membrane
• Membrane consists primarily of phospholipids
– phospholipid bilayer
inside cell
phosphate
hydrophilic
lipid
hydrophobic
outside cell
The Fluidity of Membranes
• Phospholipids in the membrane are
fluid – like (meaning they can move easily)
Lateral movement
(~107 times per second)
(a) Movement of phospholipids
Figure 7.5 A
Flip-flop
(~ once per month)
Semi-permeable membrane
• Will allow passage through the membrane
• However, it needs to control what gets in or
out
– membrane is semi-permeable
sugar
aa
lipid
H 2O
salt
NH3
So how does a semi-permeable
membrane work?
Pair and Share! Explain what happened
in the Activating Strategy.
Hypertonic, Hypotonic, & Isotonic
Type of solution
What is it
Which way will
water move
What happens to
a cell placed in the
solution?
Hypertonic
More solute
outside the cell
than inside the
cell
Outside the cell
Shrink
Hypotonic
More solute inside
the cell than
outside the cell
Inside the cell
Swell
Isotonic
Equal
concentration of
solutes inside and
outside the cell
Movement of
water is equal
nothing
Movement of water
• What will happen to a cell that is too
hypertonic?
– The cell will shrink
• What will happen to a cell that is too
hypotonic?
– The cell will burst!
Transport
• What does transport mean?
– The movement of something
• How many kinds are there?
–2
• What are they called?
– Passive transport and active transport
Passive Transport
• Definition: Movement of particles through the
plasma membrane with no energy
• Particles move down the concentration gradient
• What does this mean?
– Particles move from an area of high concentration to
low concentration
*(think of the tennis ball example)
Facilitated Diffusion
• Definition: passive transport of materials
across the membrane using transport proteins
• Channel proteins: form channels allowing
specific molecules to flow through
• Carrier proteins: change shape to allow a
substance to pass through the plasma
membrane
Channel Proteins
Permit the
passive
movement of
molecules or ions
of appropriate
size (dialysis)
through an
aqueous pore
Carrier Proteins
Bind to specific solutes to transport them across
a membrane. Examples can be facilitated
diffusion (passive) or pumps (active), like a
sodium-potassium pump.
Time Out!
From memory fill out Facilitated Diffusion
Specialized Passive Transport
• The movement of any molecule across a
selectively permeable membrane with the
concentration gradient is referred to as
Diffusion.
• The movement of H20 across a selectively
permeable membrane with the concentration
gradient is referred to as Osmosis.
Time Out!
Pair & Share: 1’s Simple Diffusion & 2’s Osmosis.
Active Transport
• Definition: Movement of particles through a
membrane against a concentration gradient
• ***REQUIRES ENERGY!!!!!!!! ***:O
• Which way do particles move??
– LOW concentration to HIGH concentration
Active Transport
• Uses carrier proteins to move particles
against the concentration gradient
Time Out!
From memory fill out Active Transport!
Passive vs. Active transport
Type of
transport
Transport
protein used
Direction of
movement
Requires
energy input
from cell?
Classification
of transport
Simple
diffusion
No
Down the
concentration
gradient
No
Passive
Facilitated
diffusion
Yes-channel
and/or carrier
proteins
Down the
concentration
gradient
No
Passive
Active
transport
Yes-carrier
proteins
Against the
concentration
gradient
yes
Active
Transport of large particles
• Endocytosis: Cell surrounds and takes in
material from the environment (Enters)
• Exocytosis: Cell expels (releases) material
from a cell (usually to remove wastes) (Exits)
Time Out!
Pair & Share: 1’s Active Transport & 2’s Passive
Transport. Then work together to complete similarities.