Download 3 Cell Boundaries powerpoint

In or Out?
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1. What are some things that can pass
through a window screen?
2. What are some things that cannot pass
through a window screen? Why is it
important to keep these things from
moving through the screen?
3. The cell is surrounded by a cell
membrane, which regulates what enters
and leaves the cell. Why is it important to
regulate what moves into and out of a cell?
Sec 7-3: Cell Boundaries
Two Types of Cell Boundaries
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1. Cell wall (outer)
 Strong supporting layer outside cell membrane
 Only in some organisms
-plants, algae, fungi, prokaryotes
 Porous
2. Cell membrane (inner)
 Thin, flexible layer that surrounds all cells
Plant Cell: Has Cell Wall and Cell Membrane
(Cell)
Functions of Cell Membrane
 1.
Regulates what goes in and
what comes out of a cell
 2.
Protects cell
 3.
Supports cell, but also
flexible
Outside
Section 7-3
of cell
Figure 7-12 The Structure of the
Cell Membrane
Structure of Cell Membrane
Carbohydrate
chains
Proteins
Cell
membrane
Inside
of cell
(cytoplasm)
Protein
channel
Lipid bilayer
Main Parts of Cell Membrane
Section 7-3
• 1. Phospholipid bilayer – 2 layers
Phospholipid
– Phosphate “head” = is polar = likes water
– Lipid “tails” = are non-polar = do not like water
(is why phospholipids align a certain way)
Phosphate head: is in water
Lipid tails: point away from water
Phosphate head: is in water
• 2. Proteins
– Embedded in lipid bilayer
– Form channels and pumps
• 3. Carbohydrates
– Allow individual cells to identify one another
• 4. Cholesterol
– Regulates membrane fluidity over wide
range of temperatures
• Warm temp. = Prevents membrane from
becoming too fluid
• Cold temp. = Prevents membrane from
becoming frozen
Membrane = Fluid Mosaic Model
Why?
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Fluid = is flexible and moveable
Mosaic = made of so many kinds of molecules
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Like mosaic artwork made of so many different tiles
Terms to Know
• A solution is a mixture of two or more
substances, evenly mixed
– Solutes = substances dissolved in the solution
• The cytoplasm is a solution of many different
substances
• Concentration = mass of solute in a given
volume of solution
– Mass/volume
Passive Transport  [High] to [Low]
Does not require energy!!!!!
• DIFFUSION
• FACILITATED
DIFFUSION
• OSMOSIS
DIFFUSION: Definition
High Concentration
MOVE from an AREA OF
HIGH CONCENTRATION
to
an AREA of LOW
CONCENTRATION
Low Concentration
Diffusion
• Def. of permeable = membrane that lets
substances pass through it
• Cell membrane is selectively permeable,
which means that it lets some things in but
does not let other things in
• Substances keep moving till there is about
equal amounts of them on both sides of the
membrane = at equilibrium
Factors that Affect Diffusion
• Amounts of substances involved
• Temperature
• Pressure
• Stirring
-speeds up the rate of diffusion
OSMOSIS
• Deals with movement of water
– From greater to lesser area of water
• Particles can’t move because membrane won’t
allow it!
Types of Solutions
(refers to solution outside of cell)
• Hypotonic (“hypo” = less)
– Less solutes outside cell = more water
– More solutes inside cell = less water
Water rushes into cell
(cell swells up like a hippo = hypo)
• Hypertonic (“hyper” = more)
– More solutes outside cell = less water
– Less solutes inside cell = more water
Water leaves cell
• Isotonic (“iso” = same)
– Same amount of solutes inside and outside cell
 Water stays where it is
Types of Solutions Examples
Osmotic Pressure
• Pressure exerted on hypertonic side of a
selectively permeable membrane
– Cell walls prevent the cell from expanding
• Some organisms fight osmotic pressure
by using a contractile vacuole – pumps
excess water out of the cell
– Ex. paramecium
Facilitated Diffusion
• Passive
– Proteins used in facilitated diffusion are called
channels
– Channels are specific to certain molecules
– 100 different protein channels
RECAP
• What are 3 major types of passive
transport?
• What characterizes these as passive?
• Describe how the concentration of
molecules moves within this type of
transport.
• What would happen to a red blood cell
placed in a hypertonic solution?
Active Transport
• ENERGY NEEDED!
Molecule to
be carried
• Molecules go from lesser to
greater concentration
“against concentration gradient”
• Also used for when LARGE
molecules need to get
through membrane
• May or may not need channel
proteins – called pumps
Energy
Molecule
being carried
Active Transport
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Active Transport Video
Endocytosis and Exocytosis
• Endocytosis = process by which cells take
in large molecules from the outside
-eg.: pinocytosis – large amounts of liquid
phagocytosis – large amounts of solid
• Exocytosis = process by which cells get rid
of large molecules in the cell; leaves cell.
• Vacuole fuses with membrane to dispel
Endocytosis and Exocytosis
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Endocytosis and Exocytosis Video
Pinocytosis
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Pinocytes are pockets on the cell
membrane.
Subtances are engulfed and a
vacuole forms around them
Phagocytosis: Engulfing
• This is when large
molecules are surrounded
and pulled into the cell
• Examples: amoeba, white
blood cells called
phagocytes
• This is the same method
used by white blood cells
to trap bacteria in our
blood
Types of Transport
ACTIVE
requires Energy
Exocystosis &
Endocytosis
PASSIVE
Does not need energy
Diffusion
Osmosis
Facilitated Diffusion
RECAP
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What are some examples of active
transport?
Describe the concentration gradient
involved in active transport
How is active transport different
from passive transport?
Exit Questions
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When is equilibrium reached?
What is the difference between
osmosis and diffusion?
What is the difference between
active and passive transport?