Download Chapter 7

Cell Structure and Transport
7-1 Objectives
• Describe the tenets of the cell theory
• Compare the characteristics of prokaryotic and
eukaryotic cells
• Describe the parts of a light and electron
microscope
Chapter 7
Cellular Structure and Function
7.1 Cell Discovery and Theory
The Cell Theory
 All organisms are composed of one or more
cells.
 The cell is the basic unit of structure and
organization of organisms.
 All cells come from preexisting cells.
Chapter 7
Cellular Structure and Function
7.1 Cell Discovery and Theory
Basic Cell Types
- All cells have a plasma membrane
Prokaryotic Cell
 Simple structure
 Contains a plasma
membrane
 Does not contain
membrane-bound
organelles
 No nucleus
11,000x
Chapter 7
Cellular Structure and Function
7.1 Cell Discovery and Theory
Eukaryotic Cell
 More complex
structure
 Contains a plasma
membrane
 Membrane cell
organelles
7.2 The Plasma Membrane
Objectives
1. Describe how a cell’s plasma membrane
functions
2. Identify the roles of proteins, carbohydrates,
and cholesterol in the plasma membrane
Chapter 7
Cellular Structure and Function
7.2 The Plasma Membrane
Plasma Membrane
 Thin, flexible boundary between the cell
and its environment
Chapter 7
Cellular Structure and Function
7.2 The Plasma Membrane
Selective Permeability
 The plasma membrane controls the movement of
substances into
and out of the cell.
Chapter 7
Cellular Structure and Function
7.2 The Plasma Membrane
 The plasma membrane is composed of the
phospholipid bilayer.
Chapter 7
Cellular Structure and Function
7.2 The Plasma Membrane
Fluid Mosaic Model
 “float” in the
membrane.
Other Components
 Proteins
 Cholesterol
 Carbohydrates
Chapter 7
Cellular Structure and Function
7.2 The Plasma Membrane
Proteins
 Transmit signals inside the cell
 support structure
 Provide pathways for substances to enter and leave
Chapter 7
Cellular Structure and Function
7.2 The Plasma Membrane
Cholesterol
 Prevents fatty acid tails from sticking together
Chapter 7
Cellular Structure and Function
7.2 The Plasma Membrane
Carbohydrates
 Identify chemical signals
• Plasma membrane
7.3 Structures and Organelles
Objectives
1. Identify the structure and function of the
parts of a typical eukaryotic cell.
2. Compare and contrast structures of plant and
animal cells.
Chapter 7
Cellular Structure and Function
7.3 Structures and Organelles
Plant and Animal Cell Structures
Animal Cell
Plant Cell
Chapter 7
Cellular Structure and Function
7.3 Structures and Organelles
Chapter 7
Cellular Structure and Function
7.3 Structures and Organelles
Chapter 7
Cellular Structure and Function
7.3 Structures and Organelles
Chapter 7
Cellular Structure and Function
7.3 Structures and Organelles
Chapter 7
Cellular Structure and Function
7.3 Structures and Organelles
Cilia
 Short, numerous
projections that look
like hairs
400x
Flagella
 Longer and less
numerous than cilia
 Create movement with
a whiplike motion
26,367x
Summary of cell parts
• http://glencoe.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::550::400::/sites/dl/free/0
078695104/383931/Table7_1a.swf::Summary%20of%20Cell%20Str
uctures%20-%20A
• http://glencoe.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::550::400::/sites/dl/free/0
078695104/383931/Table7_1b.swf::Summary%20of%20Cell%20Str
uctures%20-%20B
• http://glencoe.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::550::400::/sites/dl/free/0
078695104/383931/Table7_1c.swf::Summary%20of%20Cell%20Str
uctures%20-%20C
7.4 Cellular Transport
Objectives
1. Explain the processes of diffusion, facilitated
diffusion, and active transport
2. Predict the effect of a hypotonic, hypertonic,
or isotonic solution on a cell
3. Discuss how large particles enter and exit
cells
Cell Membranes
&
Movement Across Them
2006-2007
Cell (plasma) membrane
• Cells need an inside & an outside…
– separate cell from its environment
– cell membrane is the boundary
IN
food
- sugars
- proteins
- fats
salts
O2
H2O
cell needs materials in & products or waste out
OUT
waste
- ammonia
- salts
- CO2
- H2O
products
- proteins
Building a membrane
• How do you build a barrier that keeps the
watery contents of the cell separate from
the watery environment?
 FATS 
 LIPIDS 
Remember: oil
& water
don’t mix!!
What substance do
you know that
doesn’t mix with
water?
Lipids of cell membrane
• Membrane is made of special kind of lipid
– phospholipids
– “split personality”
“attracted to water”
• Membrane is a double layer
– phospholipid bilayer
phosphate
inside cell
lipid
outside cell
“repelled by water”
Semi-permeable membrane
• Cell membrane controls what gets in or out
• Need to allow some materials — but not all —
to pass through the membrane
– semi-permeable
• only some material can get in or out
So what needs to get across the membrane?
sugar
lipids
aa
O2
H2O
salt
waste
Crossing the cell membrane
• What molecules can get through the cell
membrane directly?
– fats and oils can pass directly through
lipid
inside cell
salt
waste
outside cell
sugar
aa
H2O
but…
what about
other stuff?
Cell membrane channels
• Need to make “doors” through membrane
– protein channels allow substances in & out
• specific channels allow specific material in & out
• H2O channel, salt channel, sugar channel, etc.
inside cell
waste
H2O
salt
aa
sugar
outside cell
How do you build a semi-permeable
cell membrane?
• Channels are made of proteins
– proteins both “like” water & “like” lipids
bi-lipid
membrane
protein channels
in bi-lipid membrane
Protein channels
• Proteins act as doors in the membrane
– channels to move specific molecules through cell
membrane
HIGH
LOW
Movement through the channel
• Why do molecules move through membrane if
you give them a channel?
HIGH
?
LOW
?
Molecules move from high to low
• Diffusion
– move from HIGH to LOW concentration
Diffusion
• Move from HIGH to LOW concentration
– passive transport
– no energy needed
diffusion
diffusion of water
osmosis
Simple Diffusion
• Move from HIGH to LOW
fat
inside cell
fat
fat
fat
fat
fat
Which way will
fat move?
LOW
HIGH
fat
outside cell
fat
fat
fat
fat
fat
fat
fat
Facilitated Diffusion
• Move from HIGH to LOW through a channel
sugar
inside cell
sugar
sugar
sugar
sugar
sugar
LOW
Which way will
sugar move?
HIGH
outside cell
sugar
sugar
sugar
sugar
sugar
sugar
sugar
Diffusion
• Move from HIGH to LOW concentration
– directly through membrane
• simple diffusion
• no energy needed
– help through a protein channel
• facilitated diffusion (with help)
• no energy needed
HIGH
LOW
Simple vs. facilitated diffusion
simple diffusion
inside cell
lipid
facilitated diffusion
inside cell
H2O
protein channel
outside cell
outside cell
H2O
Active transport
• Cells may need molecules to move against
concentration “hill”
– need to pump “uphill”
• from LOW to HIGH using energy
– protein pump
– requires energy
• ATP
ATP
Transport summary
simple
diffusion
facilitated
diffusion
active
transport
ATP
Osmosis
Movement of Water Across
Cell Membrane
2006-2007
Osmosis
• Water is very important, so we talk about
water separately
• Osmosis
– diffusion of water from HIGH concentration of
water to LOW concentration of water
• across a semi-permeable membrane
Keeping water balance
• Cell survival depends on balancing water
uptake & water loss
freshwater
balanced
saltwater
1
•
Keeping right amount of water in
cell
Freshwater
freshwater
KABOOM!
– a cell in fresh water
– high concentration of water around cell
• cell gains water
• example: Paramecium
• problem: cells gain water,
swell & can burst
– water continually enters
Paramecium cell
• solution: contractile vacuole
– pumps water out of cell
No problem,
here
Controlling water
• Contractile vacuole in Paramecium
2
Keeping right amount of water in
cell I’m shrinking,
saltwater
• Saltwater
I’m shrinking!
– a cell in salt water
– low concentration of water
around cell
• cell loses water
– example: shellfish
– problem: cell loses water
• in plants: plasmolysis
• in animals: shrinking cell
– solution: take up water
I will
survive!
3
Keeping right amount of water in
• Balanced conditionscell That’s balanced
better!
– no difference in concentration
of water between cell &
environment
• cell in equilibrium
• example: blood
• problem: none
I could
– water flows across membrane
be better…
equally,
in both directions
– volume of cell doesn’t change
Ice Fishing in Barrow
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