movement through the membrane bubble lab bubble lab section 7-3
TRANSCRIPT
MOVEMENT THROUGH THE MEMBRANEBubble 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
StructurePhospholipid 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 CellsMolecules 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
OsmosisIsotonic – 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 PracticeThe 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 TransportMoving 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 TRANSPORTMoving 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
Cells
Tissues
Organs
Organ
System
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. Explain Diffusion
2. Explain Osmosis
3. What does selectively permeable mean?
4. What is facilitated diffusion?
5. 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
= cell
10% salt
10% salt
10% salt
20% salt
20% salt
10% salt
10% salt
10% salt
10% salt
20% salt
10% salt
20% 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?
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)
