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Chapter 7
The Cell and Its Environment
The Cell Theory
1. All Organisms are made from one or more cells.
2. The cell is the basic unit of structure and function in organisms.
3. All cells are produced from other cells.
Plasma Membrane
What is it? Boundary that separates the cell from
its environment.
What is its purpose?
Controls which particles enter and leave the cell
Amino Acids
Glucose
Carbon Dioxide
This is Called “Selective Permeability”
The membrane only allows particles that are
used by the cell or expelled to cross the
membrane
Lipid Bilayer
The plasma membrane is made up of a
lipid bilayer.
What is a lipid bilayer?
Composed of Phospholipids
- two layers of phospholipids form the
plasma membrane
One end is water soluble – Phosphate group
The other end is nonsoluble. – Fatty acid end
Visual of the Lipid Bilayer
Phospholipid
Make up of the Plasma Membrane
What’s the basic structure of the Plasma Membrane?
Lipid Bilayer
Inside of the Lipid Bilayer are:
- Proteins – allow for transport of molecules
- allow for chemical reactions
- Carbohydrates – Recognition molecules
- Cholesterol – helps separate the fatty acid ends
Visual of the Plasma Membrane
Visual of the Plasma Membrane
Fluid Mosaic Model
What does it mean to be “fluid”? What is mean to be “Mosaic”?
The components of the membrane are constantly moving
Why doesn’t it break apart?
Phospholipids are:
Hydrophilic – Polar ends – attracted to H20 (dissolves)
Hydrophobic – nonpolar end – not attracted to H20
(does not dissolve)
Visual of the Fluid Mosaic Model
Membrane Function
Diffusion?
Random movement of
particles from a greater
concentration to a region
of lesser concentration
Until “dynamic equilibrium”
Osmosis
What is it?
The diffusion of water into and out of cells across a
selectively permeable membrane
Cells must maintain Osmotic Balance. Why?
More Osmosis
Even
More
Osmosis
Fig. 7-13
Isotonic solution
H2O
Hypotonic solution
H2O
H2O
Hypertonic solution
H2O
(a) Animal
cell
Lysed
H2O
Normal
H2O
Shriveled
H2O
H2O
(b) Plant
cell
Turgid (normal)
Flaccid
Plasmolyzed
Facilitated Diffusion
The transport of particles across the plasma membrane
with the use of transport proteins.
Channel Proteins (Pores)
- Allow transport of ions
- They are specific to the size and charge of the ions
Carrier Proteins – two types
- change shape to allow certain molecules to cross the
plasma membrane
2. Gates – one particle attaches to the carrier protein
changing its shape – allowing particles to freely
pass across the membrane.
Visual of Facilitated Diffusion
More Facilitated Diffusion
Active Transport
Movement of particles from an area lesser concentration to an
area of greater concentration
The transport proteins for active transport are called “pumps”
It costs the cell energy – that’s the difference between facilitated and
active transport
Visual of Active Transport
Review Passive & Active Transport
Endocytosis and Exocytosis
Endocytosis – the plasma membrane surrounds and takes in
substances from the environment
Exocytosis – removal of substances from the cell, opposite
of Endocytosis
Endocytosis – Phagocytosis
Phagocytosis – solid chunks of material are taken into the cell
Endocytosis – Pinocytosis
Pinocytosis – liquid is taken into the cell
Endocytosis – Receptor-Aided
Protein Receptors identify specific particles for endocytosis
Endocytosis
Review - In your lab groups answer the following questions.
Define part “A” and “B” of the Molecule Below.
A
B
Explain how each part of the molecule behaves in H20?
Review
Draw the arrangement of Molecules that make up the
plasma membrane.
1. Explain the function of each molecule.
2. What makes the plasma membrane permeable to Water?
3. What does it mean to be selectively permeable?
Review
What process causes water to enter a single cell organism?
What is this Process called?
What would happen to a single cell pond organism that was placed
into pure water? Why?
What would happen to a single cell pond organism that was placed
into salt water? Why?
Review
Diagram and explain the similarities and differences of the following:
1. Diffusion, Osmosis and Facilitated Diffusion.
2. Channel Proteins, Carrier Proteins and Gate Proteins.
3. Phagocytosis, Pinocytosis and Receptor-aided endocytosis.
Answer to #2
Channel Proteins (Pores)
- Allow transport of ions
- They are specific to the size and charge of the ions
Carrier Proteins – two types
1. change shape to allow certain molecules to cross the
plasma membrane
2. Gates – one particle attaches to he carrier protein
changing its shape – allowing particles to freely
pass across the membrane.
Review
Explain the difference between Active and Passive Transport.