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THE WORKING CELL (CH 5)
NUCLEUS
Nuclear envelope
Nucleolus
Rough
endoplasmic
reticulum
CYTOSKELETON
Microtubule
Microfilament
Intermediate
filament
Ribosomes
Smooth
endoplasmic
reticulum
Plasma
membrane
Golgi apparatus
Lysosome
Mitochondrion
Centrosome
with pair of
centrioles
TRANSPORT OF LARGE MOLECULES
Endocytosis transport large molecules
Phagocytosis “cell eating”
• Engulf the food
• Package in a membrane enclosed vacuole
• Lysosomes digest it!
Pseudopodium
“Food” or
other particle
Food
vacuole
Receptor
Specific
molecule
Coated
pit
Receptor mediated endocytosis
• Receptor proteins
• Package in a membrane enclosed vacuole
• Lysosomes digest it!
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TRANSPORT OF LARGE MOLECULES
Exocytosis and endocytosis transport large molecules
Exocytosis “exports” large molecules
1. Molecule in a membrane enclosed vesicle
moves from Golgi apparatus to membrane
2. Vesicle fuses with plasma membrane
3. Molecules spill out of cell
CELL MEMBRANES Small molecules and ions move across membranes or through protein channels.
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DIFFUSION The tendency of a particle to move along a concentration gradient
DIFFUSION The tendency of a particle to spread out into available space
(along a concentration gradient)
Molecules of dye
Membrane
Pores
Net diffusion
Net diffusion
Equilibrium
FIG 5.3A
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PASSIVE TRANSPORT
• Diffusion of molecules across a cellular membrane
• Requires no energy
CO2
O2
FACILITATED DIFFUSION Diffusion of polar molecules with the help of transport proteins
Polar molecule
• Specific
transport proteins for specific types of molecules
• Aquaporins
transport water across cell membranes
Transport
protein
FIG 5.6
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WATER TRANSPORT IN A CELL
Think about a cell full of pure water, in a cup of pure water. Easy right?
H2O
H2O
WHAT IF THE CELL IS IN A SOLUTION?
Solution: a liquid consisting of a uniform mixture of two or more substances
• SOLUTION = Solute(s) + solvent
• SOLUTE= the substance that is dissolved
• SOLVENT= the dissolving agent
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TABLE SALT IN WATER
Na
Na
Sodium atom
Cl
•
•
•
•
Salts are formed by ionic bonds
Strong in air
Bonds break in water
Form Na+ and Cl‐ ions
Cl
Chlorine atom
Cl−
Na+
FIG 2.7 A,B
WATER TRANSPORT IN CELLS
• In a solution, water molecules bond with solute molecules
• Creates a gradient of “free” water molecules
(Diffusion is the tendency of a particle to move along a concentration gradient)
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WATER TRANSPORT IN CELLS
• Water molecules can move across aquaporin channels but solute molecules cannot.
• A gradient of “free” water molecules is created
• Water molecules move along the concentration gradient of “free molecules”
OSMOSIS
The diffusion of water across a SELECTIVELY permeable membrane
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TYPES OF SOLUTIONS
TONICITY ‐ the ability of a solution to cause a cell to gain or lose water
Less solutes outside than inside cell
Solutes are the same inside and outside cell
More solutes outside than inside cell
CELL WATER BALANCE IN SOLUTIONS
Hypotonic solution
H2O
Lysed
Isotonic solution
Hypertonic solution
H2O
H2O
Normal
H2O
Shriveled
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WATER BALANCE
Cell walls prevent lysing in hypotonic solutions
Hypotonic solution
Isotonic solution
Plasma
membrane
H2O
H2O
Lysed
Hypertonic solution
Normal
Flaccid
Turgid (normal)
H2O
Shriveled
Shriveled (plasmolyzed)
Osmoregulation: an organism’s control of water balance
WATER BALANCE
Cell walls prevent lysing in hypotonic solutions
Hypotonic solution
Isotonic solution
Plasma
membrane
H2O
H2O
Lysed
Turgid (normal)
Hypertonic solution
Normal
Flaccid
H2O
Shriveled
Shriveled (plasmolyzed)
Osmoregulation: an organism’s control of water balance
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MOVEMENT ACROSS MEMBRANES
Passive transport
1. Non polar molecules pass across membranes via DIFFUSION
O2
CO2
2. Polar molecules pass across specific channel proteins via FACILITATED DIFFUSION
3. Water molecules pass along aquaporins via FACILITATED DIFFUSION and transport is affected by the process of OSMOSIS
H2O
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MOVEMENT ACROSS MEMBRANES Active transport: moving a solute AGAINST the concentration gradient
Transport
protein
• Active transport proteins move molecules in or out of cells AGAINST the concentration gradient
• Specific transport proteins for specific molecules
Requires ENERGY
Solute
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ACTIVE TRANSPORT
Active transport: moving a solute AGAINST the concentration gradient
Transport
protein
Energy
Solute
1 Solute binds
to transport
protein.
2 Energy is
added to
change the
protein shape.
3 Protein returns
to original shape
and more solute
can bind.
ENERGY
The capacity to cause change or to perform work
1. Kinetic Energy: the energy of motion
• Thermal energy (heat) – energy of atoms vibrating back and forth
• Sound
• Electricity
• Light
2. Potential Energy: energy resulting from location or structure
• Chemical • Gravitational
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CHEMICAL ENERGY
Cells use potential chemical energy to perform work
Potential energy is the energy matter pocesses as a result of it’s location or structure
ENERGY TRANSFORMATION
Laws of thermodynamics
1. Energy can not be created or destroyed
2. Energy transforms increase entropy of the universe
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ENERGY TRANSFORMATION
Laws of thermodynamics
2. Energy transforms increase entropy of the universe
• Energy is given off as heat in each energy transfer
• The original energy becomes more disorganized (i.e. entropy increases) at each step.
THURSDAY
Details of how energy is transferred and renewed in cells End of CH4, beginning of CH5
• Requires ENERGY
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TODAY’s CHECK‐IN (3pts)
Open Notebook & NOTHING ELSE!
1. If an animal cell containing 2% of polar molecule “A” is put into a solution containing 50% of molecule “A”, based on what we know about osmosis, what will happen to water molecules inside the animal cell? (1pt) 2. What if it is a plant cell? (1pt) .
3. RATE YOUR UNDERSTANDING
A) Easy money
B) I should probably review passive transport
C) This was hard, I should probably stop by for office hours to clarify.
REQUIRED VIDEO
This core concepts of this material is fair game for our next check‐in AND ALL EXAMS!
ALL OF THE ENERGY OF THE UNIVERSE IS….
See link on the course website: http://www.biosbcc.net/harrer
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