Download Chapter 7: Cell Structure and Function The

Cell Boundaries
7-3
All cells are surrounded by a thin barrier
called the cell membrane.
Many cells also have a strong supporting layer
around that membrane called the cell wall.
Cell membrane
Cell wall
Cell Membrane
 Cell membranes regulate what enters & leaves
a cell.
 They also aid in protection & support.
 Nearly all cell membranes are a flexible,
double layered sheet
called a lipid bilayer.
P. 184, fig. 7-15
Along w/ lipids,
the cell membrane
also has proteins &
carbohydrates
embedded in it.
The lipid bilayer is
often called a mosaic,
b/c it is
made up of many
different parts.
The proteins form channels & pumps for
moving materials across the membrane.
The carbohydrates act like ID cards, allowing
individual cells to identify one another.
• http://www.youtube.com/watch?v=Qqsf_UJcf
Bc&feature=related
• http://www.youtube.com/watch?v=vh5dhjXzb
Xc
Cell Walls (CW’s)
• Found in:
– Plants
– Algae (Protists)
– Fungi
– Many prokaryotes
Ragweed
(not all)
• CW’s lie outside the
cell membrane.
Onion
• Most cell walls allow certain substances to
pass through.
• Such as:
– H20
– CO2
– O2
Main function is to support & protect the cell.
• Most Cell Walls
are made of fibers
of carbohydrate &
protein.
Plant CW’s are made of cellulose.
Cellulose is a tough carbohydrate fiber.
The fiber in your diet.
Diffusion Through Cell Boundaries
The movement of molecules from one side of
the cell membrane to the other.
Measuring Concentration
• Recall what a solution is.
– What’s a solute?
– What’s a solvent?
• Concentration –the mass of solute in a given
volume of solution, or mass/volume.
• Lets figure concentration of a solution.
– If you dissolved 12g of salt in 3L of water, the
concentration would be: 12g/3L = 4 g/L
Diffusion
• Diffusion –process of molecules moving from an
area of high concentration to an area of low
concentration.
– Equilibrium –when the concentration of a solute is the
same throughout a solution.
What does diffusion have to do w/ a cell membrane?
P. 184, fig. 7-14
Diffusion requires no E output by the cell.
It’s free!
Diffusion will continue until equilibrium is reached
Osmosis
• Biological membranes are selectively permeable.
– Some substances can pass & some can’t.
• Water passes very easily.
• However, many solutes can’t.
• Osmosis –the diffusion of water through a selectively
permeable membrane.
How Osmosis Works
• H2O moves from an area of high H2O
concentration to an area of low H2O
concentration.
• Water moves across the membrane until EQ is
reached.
Osmosis
Section 7-3
• http://www.youtube.com/watch?v=sdiJtDRJQ
Ec&feature=related
3 types of Osmotic Solutions:
P. 186, fig. 7-16
 Isotonic
– Concentrations are equal on both sides of the membrane.
– Normal looking cells
 Hypertonic
– Solution outside the cell has a higher solute concentration than the
inside of the cell.
– Water leaves the cell.
–
Cells shrink
 Hypotonic
– Solution has a lower solute concentration than the cell.
– Water enters the cell.
– Cells swell
Plant Cells
Plant Cells
• http://www.youtube.com/watch?v=GOxouJUt
EhE&feature=related
Turgid
Flaccid
Red Blood Cells
Osmotic Pressure
• Osmosis exerts a pressure known as osmotic
pressure.
• Osmotic pressure -the pressure exerted by the flow
of water through a semi permeable membrane.
• This can cause serious problems for a cell.
– Cells can swell to the point of bursting.
• Fortunately, animal cells are in a isotonic
solution & don’t come into contact w/ pure
H2O.
– If they did they would burst.
• Also, plant cells & bacterial cells have cell
walls that prevent the cell from bursting.
Facilitated Diffusion
• Facilitated diffusion –movement of specific
molecules across CM’s via protein channels.
– P. 187, fig. 7-17
• There are hundreds of protein channels that
allow only certain substances to cross
different membranes.
This process does not require E.
It acts just as diffusion.
– It goes from high to low concentrations.
Facilitated Diffusion
• http://www.d.umn.edu/~sdowning/Membran
es/diffusionanimation.html
Active Transport
When cells move materials against the
concentration gradient, they are using Active
Transport.
– This process requires E.
Active transport is carried out by transport
proteins or pumps found in the membrane.
Endocytosis
•
Transport of larger molecules
can be done through 2 active
transport processes:
1. Endocytosis
–
P. 188, fig. 7-18
2. Exocytosis
For each of these
processes, the shape
of the membrane
changes.
Exocytosis
Endo & Exo
• http://www.youtube.com/watch?v=K7yku3sa
4Y8&feature=related
Molecular Transport
•
Endocytosis –process of taking material into the
cell by infolding or pocketing of the CM.
– This process forms a vacuole in the cell.
– This process works for:
•
•
•
taking in food
larger molecules
other cells
– 2 examples of endocytosis are:
•
•
Phagocytosis
Pinocytosis
• Phagocytosis – extensions of cytoplasm
surround a particle & package it w/in food
vesicles.
– Amoebas use this method
• Fig. 7-18
• Pinocytosis –the process of taking in liquids
from the surrounding environment.
Many cells also release large amounts of
material from the cell.
This process is called exocytosis.
Ex:
– The removal of water by a contractile vacuole is an
example of this kind of active transport.
• http://highered.mcgrawhill.com/sites/0072437316/student_view0/ch
apter6/animations.html#
Section 7-4
The Diversity of Cellular Life
Single-celled Organisms
a.k.a.
Unicellular orgs. – made of one cell
Unicellular orgs. can:
– grow
– respond to the env.
– reproduce
– transform E
Yeast
Leptospira bacteria
Star sand
Unicellular orgs. dominate life on Earth.
Paramecium
Volvox aureus
Staphylococcus aureus
Examples p. 190 fig. 7-21
Multicellular Organisms
Multicellular org. - made up of many cells.
Cells are specialized
• Cell Specialization – process in which cells develop in
different ways to perform different tasks.
Red blood cells
Pancreatic cells
Muscle cells
See p. 91, fig. 7-22
Specialized Animal Cells
• Examples of specialized cells in animals:
– Red blood cells
• Transport O2 throughout the body.
– Pancreatic cells
• Produce enzymes that aid in digestion.
• Contain cells specialized for making proteins.
– These cells have numerous ribosomes.
– Muscle cells
• Able to contract & relax, causing movement of our
bones.
Where in the human body do you think you would find
cells that are specialized to produce digestive enzymes?
?
These cells are found in the human trachea. What do you
think they are specialized to do?
Specialized Plant Cells
• Guard cells of the stomata:
– Monitor a plants internal conditions, & makes
changes accordingly.
Tomato leaf stomata
Levels of Organization
The levels of organization in a multicellular org.
are as follows:
1.
2.
3.
4.
5.
Individual Cells
Tissues
Organs
Organ system
Organism
 P. 192, fig. 7-22
Examples
neurons (nerve cells)  nervous tissue  brain  central nervous system
muscle cell  smooth muscle tissue  stomach  digestive system
Specialized cells play different roles
Tissue – a group of similar cells that perform a specific function
Example: The collection of cells in the pancreas that make proteins.
There are 4 main
types of tissue in
multicellular
organisms :
• Muscle
• Epithelial
• Nervous
• Connective
• Organs – many groups of tissues working together.
– Each muscle is an organ.
– However, the muscle also contains nervous tissue
& connective tx.
(abbr. = tx)
• Organ system – a group of organs working
together to perform a specific function.
– Digestive system
– Circulatory system
– Reproductive system
– Nervous system
Altogether, organ systems make up the organism.
Body Systems