1. Chapter 7 III. Cell Boundaries

2. All cells have a _____________________________and some have a cell wall
Cell membrane

3. 1. What are some things that can pass through a window screen?
Interest Grabber
Section 7-3
How is a window screen similar to a cell membrane? Read on to find out.
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?
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4. A. Cell Membrane Fluid mosaic Phospholipid bilayer
Regulates what enters and leaves the cell and also provides _____________________________.
Almost all cell membranes are made of a double layered sheet called a ___________________________-flexible,yet strong barrier
Cell membranes usually have a protein molecule imbedded in the bilayer w/ carbohydrate molecules attached
Called a _________________model
Some of the proteins form channels or pumps to move material across the membranes
Some of the carbs act as ____________________tags
Fluid mosaic
Phospholipid bilayer
Protection and support
Chemical id tags

6. Figure 7-15 The Structure of the Cell Membrane
Section 7-3
Outside
of cell
Cell
membrane
Proteins
Protein
channel
Lipid bilayer
Carbohydrate
chains
Inside
of cell
(cytoplasm)
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7. B. Cell Walls In plants,algae,fungi, and many prokaryotes
Lie _______________the cell membrane
Usually porous enough to let water,O2,CO2 and certain other substances to pass through easily
Main function is support and protection
Usually made of fibers of ____________________-produced in cell and secreted to surface
Mostly _____________________-tough carb fibers
cellulose
Carbohydrate and protein
outside

8. C.Diffusion Through Cell Boundaries
Every cell is in a liquid environment
Cell membrane regulates the movement of cell materials from one side to the other

9. 1.Measuring concentration
Cytoplasm is a solution of various substances in water
_____________of a solution is the mass of solute in given volume of solution---ie. Mass/volume…..If you have 15 g salt in 3 mL water,what is the concentration?------_______….If you have 24 g salt in 2mL water you would have 12 g/mL salt….Which solution is more concentrated?______________
12 g/mL
5g/mL
concentration

10. 2. Diffusion
In a solution the particles move constantly,spreading out randomly….tending to move where more concentrated to an area less concentrated…This is called __________________.
____________________= concentration of a solute is the same throughout a system
does not require energy because random movement
if equilibrium is reached,particles keep moving across the membrane,still balancing concentration
isotonic

12. D. Osmosis

13. Figure 7-17 Osmosis Cell membrane Section 7-3 Water molecules
Higher Concentration
of Water
Cell
membrane
Lower Concentration
of Water
Sugar molecules
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14. D. Osmosis
Some molecules are too large or too strongly charged to make it across the lipid bilayer----thus impermeable to it
Most membranes are selectively permeable
_____________________is the diffusion of water across a selectively permeable membrane
water moves easily and will move to balance the concentration of a solute,water moving from area of higher to lesser conc. For the WATER
____________________-same strength of a solute on both sides of a cell membrane
isotonic
osmosis

15. more concentrated side of solute is ____________________
less concentrated side is____________________
Osmosis exerts a pressure known as ____________________________on the hypertonic side of a membrane….This could results in a cell bursting
Bursting not so much a problem in larger organisms….tend to be in isotonic environments
Osmotic pressure may not allow a plant or bacterial cell to burst , but could weaken the cell wall
Osmotic pressure
hypotonic
hypertonic

16. E.Facilitated Diffusion
Some molecules,like glucose ,diffuse quickly across due to ________________________
These allow only certain molecules to pass
Since it is diffusion it does not require energy and still goes from area of higher to lower concentration
Protein channels

18. F.Active Transport--- Requires much energy
_______________________________________________________________________________
Requires much energy
Usually carried out by proteins or pumps found in the membrane
Moves materials across a concentration gradient,or difference

19. 1. Molecular Transport Ca ,K,and Na ions are carried
Small molecules and ions carried by proteins that act like energy requiring pumps
Ca ,K,and Na ions are carried

20. Endocytosis and Exocytosis
Transports larger molecules and even clumps of matter
________________________is the process of taking material inward by enfolding,or pockets
In endocytosis ,the pocket breaks loose from the cell membrane and forms a vacuole…large molecules,food and even whole cells can be taken in this way
endocytosis

21. 2 examples of endocytosis are
___________________-extensions of cytoplasm surround a particle and package it in a food vacuole,then the cell engulfs it ---This is how amoebas eat-----is a form of active transport
_______________-Cells use this to take up liquids in the environment—tiny pockets filled w/ liquid form along the cell membrane and pinch off to form vacuoles
phagocytosis
pinocytosis

22. ___________________________--releases large amounts from the cell by pinching off or a contractile vacuole as in paramecium---also active transport
exocytosis

23. Figure7-20 Active Transport
Section 7-3
Molecule to
be carried
Low
Concentration
Cell
Membrane
High
Concentration
Molecule
being carried
Low
Concentration
Cell
Membrane
High
Concentration
Energy
Energy
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