Download Membrane structure, I

Cell Membrane
Outside
of cell
Proteins
Carbohydrate
chains
Cell
membrane
Inside
of cell
(cytoplasm)
Protein
channel
Lipid bilayer
Membrane structure
 Semi-Permeable
 Selectively Permeable
 Amphipathic~
hydrophobic & hydrophilic
regions
 Fluid Mosaic Model
The Structure of the Cell Membrane
Outside
of cell
Proteins
Carbohydrate
chains
Cell
membrane
Inside
Protein
of cell
(cytoplasm) channel
Lipid bilayer
Membrane structure
 Phospholipids~ membrane fluidity
 Cholesterol~ membrane stabilization and
fluidity
 “Mosaic” Structure~
 Integral proteins~ transmembrane proteins
 Peripheral proteins~ surface of membrane
proteins
 Membrane carbohydrates ~ cell to cell
recognition;
Random movement results in
Solution – mixture of solute and solvent
Solute – substance being dissolved
Solvent – substance dissolving solute

Living Things (Universal Solvent)-Water
Membrane traffic
Passive transport~ diffusion
of a substance across a
biological membrane
(NO ENERGY)
[] = concentration
Diffusion~ the overall
movement of particles from a
region of high [] to an area of
low []

Osmosis~ the diffusion of
water across a selectively
permeable membrane
Results of Diffusion
Dynamic equilibrium

Once diffusion has evenly distributed the solute
throughout the solvent; movement of particles
continues with no change in []
Homeostasis

Preservation of equilibrium
Diffusion depends on [] gradient
[] gradient: the difference in [] of a
substance across space
Diffusion is said to move down a []
gradient
Diffusion continues until there is NO []
gradient
Ex: O2 diffuses into oxygen depleted blood
Diffusion
molecules like WATER,
OXYGEN, AND CARBON
DIOXIDE can move in and out
freely.
Small
Large
molecules like
PROTEINS AND
CARBOHYDRATES CANNOT
Charged
IONS CANNOT
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Osmosis
Osmosis~ the diffusion of water across a
selectively permeable membrane
Questions
Osmosis is the diffusion of _______ across a cell
membrane.
Osmosis and Diffusion are both types of
__________ transport.
Passive transport does or does not require energy?
Small molecules can not move across freely. T or F
Large molecules can move freely. T or F
Three Different Types of
Solutions
Isotonic Solution
Hypotonic
Solution
Hypertonic
Solution
Isotonic Solution
The solute outside the cell is equal in
concentration to the solute in the cell.
The cell retains its shape.
water moves equally in both directions
Hypotonic Solutions
Solution outside the blood cell contains a lower [] of
solute than inside of the cell.
Water will diffuse in.

cell will lyse (burst).
Animal cells - cytolysis.
 Plant cells do not burst- turgur pressure—
grocers use this idea
Cells in a Hypotonic Solution
Hypertonic Solutions
The solution outside the cell has a higher [] of
solute than inside of the cell.
Water will diffuse out of the cell,


causing the cell to shrink
or crenate
Why should you not salt meat before cooking?
CRENATION
PLASMOLYSIS
Cells in a Hypertonic Solution
In what type of solution would these
cells be found?
Water balance Summary
Osmoregulation~
control of water balance
Hypertonic~ higher
concentration of solutes
Hypotonic~ lower
concentration of solutes
Isotonic~ equal
concentrations of solutes
Water balance Summary
Osmoregulation~ control
in cells with cell walls:
 Turgid (very firm) - Hypo
 Flaccid (limp) - Iso
 Plasmolysis~ Hyper

plasma membrane pulls away
from cell wall
Plasmolysis
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QuickTime™ and a
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Turgidity
Other Ways to Transport Molecules
Across the
Plasma Membrane
Selective Transport
Review Covered Passive
Transport
Osmosis
Does it require energy?
NO!!!
Diffusion
Does it require energy?
NO!!!
Osmosis
What is osmosis? WATER
The movement of ___________ across the
cell membrane.
Is it the movement of any other substance?
NO!!!!
Diffusion
Mixing of two substances by the random
motion of molecules.
Molecules move from a region of high
concentration to an area of low
concentration.
How do other molecules cross the
cell membrane???
Selective Transport


Facilitated Diffusion (Another Passive Transport)
Active Transport
• Protein Pumps
• Endocytosis
• Exocytosis
Selective Transport
There are two types of selective transport

Facilitated Diffusion
• DOES NOT require the use of energy

Active Transport
• DOES require the use of energy
Facilitated Diffusion
Glucose
molecules
High
Concentration
Cell
Membrane
Low
Concentration
Protein
channel
Facilitated Diffusion
Does facilitated diffusion require the use of
energy?
NO!!!!
It uses a [] gradient to transport molecules
The molecules move from an area of high [] to an
area of low []
Most SUGAR molecules pass across the cell
membrane by this method of transport
Carrier Proteins Carry Molecules
Across the Membrane
Good Example - transport of Glucose into the Cell
Active Transport
Does active transport require the use of
energy?
YES!!!
It uses ATP
Transports against the [] gradient.
Low to High []
Sodium Potassium Pump, Endocytosis and
Exocytosis
Active Transport
Molecule to
be carried
Energy
Molecule
being carried
Active Transport:
Sodium Potassium Pump
Move Sodium out of the
cell
Move Potassium into the
cell
Uses energy (ATP)
Causes the protein to
change shape
Move against a [] gradient
Sodium Potassium Pump
Bulk Transport-Active
Endocytosis


Pinocytosis
Phagocytosis
Exocytosis
Endocytosis
During
ENDOCYTOSIS the
Cell Membrane folds
into a POUCH
(Vescicle) that
Encloses the Particles.
Two Types of Endocytosis:
Pinocytosis and Phagocytosis
PINOCYTOSIS ---"CELL DRINKING“—Small
Particles
PHAGOCYTOSIS---- "CELL EATING“-Large
Particles
Treatments
Exocytosis
EXOCYTOSIS is the
opposite OR reverse of
ENDOCYTOSIS.
EXOCYTOSIS, wastes and
cell products leave the cell.
Specialized Transport Summary
Transport proteins
 Facilitated diffusion~
passage of molecules and
ions with transport
proteins across a
membrane down the []
gradient
 Active transport~
movement of a substance
against its [] gradient with
the help of cellular energy
Elaborate
Cell Membrane Bubbles
Cellular Transport Flow Chart