Transcript Cell Transport Notes PPT

MOVEMENT THROUGH THE
MEMBRANE
Bubble Lab
Section 7-3
The cell membrane
• Function:
• Regulates what enters and leaves the cell.
Provides protection and support
• Selective permeability
• Some substances can pass across the cell
membrane and others can’t
Structure
Phospholipid Bilayer (Fluid Mosaic Model): a
double-layer sheet that makes up cell
membranes.
Components of the lipid bilayer
• Polar Head
– Hydrophilic
“Water Loving”
• Lipid Tails
– Hydrophobic
“Water Fearing”
Why is the lipid bilayer important?
• Tough, flexible structure
• Strong barrier between the cell
and its environment
What does it do for the cell?
• Allows only certain materials in or
out at certain times.
Ex. Ions (electrolytes)
Glucose
Water
Oxygen
Carbon dioxide
Other membrane structures
• Protein molecules
–Form channels and pumps that help
to move material across the
membrane
Other Membrane Structures
• Carbohydrate molecules
–Act like ID markers for the cell
–Basis for blood typing: the antigens
on the blood cells (A, B, AB) are
carbohydrate chains
Diffusion
Definition: The movement of molecules from
an area of higher concentration to an area
of lower concentration, until equilibrium is
reached.
Equilibrium – concentrations of molecules
are the same in all areas
Diffusion of Molecules
What causes diffusion?
• Diffusion is caused by the constant
movement and collision of molecules.
More molecules = More collision
• The collisions cause the molecules to
spread out.
Diffusion in Cells
Molecules are able to diffuse through the
cell membrane and allow the cell to
function.
Facilitated Diffusion – some molecules need
help from protein channels to cross the
cell membrane.
Animation
Osmosis (A special kind of diffusion)
Osmosis is the diffusion of water molecules
through a selectively permeable membrane.
Selectively permeable? only certain
substances can pass through the membrane
Selectively Permeable - Osmosis
Osmosis
Isotonic – concentration of solute is the same on
both sides of the membrane (equilibrium)
Hypertonic – the solution with a higher
concentration of solute
Hypotonic – the solution with a lower
concentration of solute
Osmosis Practice
The cytoplasm of Elodea cells is composed of
about 70% water molecules and 30% other
kinds of molecules.
What happens when the Elodea cells are put into
a liquid that is
a. 50 percent water.
b. 70 percent water.
c. 100 percent water .
Passive Transport
Moving down a concentration
gradient is like riding a bike
down a hill. It doesn’t require
energy, goes high to low.
Osmosis, diffusion and
facilitated diffusion are
examples of passive transport!
ACTIVE TRANSPORT
Moving up a concentration
gradient is like riding up a hill.
IT REQUIRES ENERGY.
Active Transport
• Active Transport: is the movement of
materials through a cell membrane using
energy.
• Molecules move from low concentration to high
concentration.
• Protein pumps use ATP to pump ions and
small molecules against concentration
gradient.
Other types of Active Transport
1. Endocytosis – the process of taking
material into the cell by means of
infoldings of the cell membrane.
– Phagocytosis – extension of the cytoplasm
surround and engulf the particle
– Pinocytosis – similar to phagocytosis, but
cells take up liquid instead of particles.
Types of Active Transport
2. Exocytosis
– Large molecules move from inside the cell to
outside the cell.
– Contractile Vacoule – an organelle that
constantly pumps H2O out of the cell.
Animation
7.4 Specialized Cells
• Cells with a specific structure and
function and are found in multi-celled
organisms.
• We have blood cells, brain cells, bone
cells, liver cell, skin cells, etc.
We are all made of cells
Organ
System
Organs
Tissues
Cells
Tissue
• Definition: A group of similar cells
working together.
• Examples
Organs
• Definition: A groups of tissues working
together to perform a specific job.
Organ Systems
•
Definition: Many organs working
together to do a specific job.
7.3-7.4 Wrap up Questions
1.
2.
3.
4.
5.
Explain Diffusion
Explain Osmosis
What does selectively permeable mean?
What is facilitated diffusion?
Are phospholipids the only molecules in a
cell membrane?
6. What is active transport?
7. What are tissues, organs, and organ
systems? Give Examples
= cell
10%
salt
10%
salt
10%
salt
20%
salt
20%
salt
10%
salt
Label the environment around the cell in each beaker as hypertonic, hypotonic or isotonic.
Label the net flow of water and state what will happen to the cell in each beaker?
= cell 10%
salt
10%
salt
10%
salt
20%
salt
20%
salt
10%
salt
Label the environment around the cell in each beaker as hypertonic, hypotonic or isotonic.
Label the net flow of water and state what will happen to the cell in each beaker?
= cell
10%
salt
10%
salt
10%
salt
20%
salt
20%
salt
10%
salt
Label the environment around the cell in each beaker as hypertonic, hypotonic or isotonic.
Label the net flow of water and state what will happen to the cell in each beaker?
Cell membrane reading
questions
1. Compare and contrast integral and
peripheral proteins.
Integral proteins span the width of the
membrane, some have a hydrophilic channel
(channel protein) to transport hydrophilic
substances into or out of the cell.
Peripheral proteins are really appendages
bound to the surface of the membrane that tie
into the cytoskeleton and provide support.
Cell membrane reading
questions
2. What are the differences between the two
types of transport proteins discussed in the
article (use figure 7.10 to help you)
One type has a hydrophilic channel selective for
a particular solute. The second shuttles a
substance from one side to the other by
changing shape (carrier proteins and protein
pumps) Some use ATP as an energy source
Cell membrane reading
questions
3. Why are proteins so essential to keeping
your cells hydrated?
The aquaporin is a channel protein that
tremendously increase the rate at which water
can enter the cell (3 billion per second)
Cell membrane reading
questions
4. Explain how diffusion relates to a
concentration gradient.
Molecules spread out evenly into available
space. Each moves randomly, but directional
from high to low concentration gradient (“down”
the concentration gradient)