1. Cell Membrane• phospholipid and protein “skin”

around cytoplasm

• found in all cells

• SELECTIVELY PERMEABLE – • some molecules easily cross the

cell membrane (CM)• others not at all

• protection

• communication

• fluid mosaic model – phospholipids and proteins move side to side

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1. Membrane Lipids

• phospholipid bilayer• polar (hydrophilic)

phosphate “head”• two, nonpolar (hydrophobic)

fatty acid tails

• heads point outward

• tails on interior of CM

• steroids• animal cells – cholesterol• plant cells – different steroid

molecules

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1. Membrane Proteins

• peripheral (sides) proteins• on interior and exterior

of CM

• Integral (within) proteins• some extend across

CM• form channels• bind and carry

molecules• others do not

• hold adjoining cells together

• viruses, hormones attach to these proteins

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Phospholipids

Integral proteinPeripheral protein

Fatty acid “tails” (lipids)

Phosphate Group

2. Passive Transport• movement of molecules

from HIGH concentration to LOW concentration• NO ENERGY (ATP)

input needed• molecules MOVE

DOWN the concentration gradient

• TYPES of passive transport• simple diffusion• facilitated

diffusion• osmosis

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high

low

ANIMATION – passive transport

3. Examples of Simple Diffusion

• perfume sprayed in an enclosed space

• sugar cube (solute) dissolving in water (solvent)

• food coloring in water• molecules in constant

motion• MOVE DOWN the

concentration gradient

• when equilibrium reached – molecules still move, stay spread out

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ANIMATION – simple diffusion

4. Diffusion Across Membranes

• molecules that CAN diffuse across the cell membrane

• high to low

• molecules that can dissolve in lipids can diffuse across the membrane

• carbon dioxide (CO2), oxygen (O2) – simple diffusion

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ANIMATION – transport across the cell membrane

4. Diffusion Across Membranes

• molecules that CANNOT diffuse across the cell membrane• ions (need ion

channels)• glucose (small,

hydrophilic, need carrier proteins)

• macromolecules – proteins (exocytosis used), RNA

• water (VERY small, polar, needs aquaporin protein)

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ANIMATION – transport across the cell membrane

5. Factors that Affect Diffusion

• steepness of concentration gradient (the difference in the concentration of molecules across a space)

• temperature

• charge

• diameter of the diffusing molecules

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6. Equilibrium• the concentration of

the molecules is the same across a space

• GOAL of diffusion is to reach equilibrium

• molecules still move, but there is no concentration gradient

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7. Osmosis• the process by which

water molecules diffuse across a cell membrane from high to low concentration

• NO ENERGY (ATP) input needed

• molecules MOVE DOWN the concentration gradient

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8. HypOtonic• the concentration of

solute molecules outside the cell is lower than the concentration inside the cell • water diffuses INTO

the cell until equilibrium is reached

• water molecules MOVE DOWN the concentration gradient

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Draw and label your arrow to show the flow of water:

hypO hyper

9. Hypertonic• the concentration of

solute molecules outside the cell is higher than the concentration inside the cell • water diffuses OUT

OF the cell until equilibrium is reached

• water molecules MOVE DOWN the concentration gradient

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Draw and label your arrow to show the flow of water:

hypO hyper

10. Isotonic• the concentration of

solutes outside and inside the cell are equal

• water diffuses INTO and OUT OF the cell at the same rate

• no net movement of water

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11. How Cells Deal With Osmosis

• osmoregulation in freshwater fish• keep body fluids

from being too dilute or too concentrated

• having to pee after swimming in a pool

• contractile vacuoles• organelles that

remove water• found in unicellular,

freshwater organisms

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Contractile vacuole video clip

12. Turgor Pressure• the pressure that

water molecules exert against the cell wall in plant cells

• plants in a hypOtonic environment

• water diffuses INTO the plant cells and stored in the central vacuole

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13. Plasmolysis• loss pressure between

the CW and CM in a plant cell• plants in a

hypertonic environment

• water diffuses OUT of central vacuole

• CM pulls away from CW

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14. Cytolysis• cell bursting

• animal cells in a hypOtonic environment

• water diffuses INTO the cell

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15. Crenation• cell shrinking

• animal cells in a hypertonic environment

• water diffuses OUT OF the cell

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16. Facilitated Diffusion• type of passive

transport (no ATP, high to low)• molecules move

DOWN the concentration gradient

• some molecules can’t easily diffuse across the CM

• need a specific integral membrane protein (IMP)

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high

low

16. Carrier Proteins – using glucose as an example

• carrier protein = specific IMP

• binds to glucose

• carrier protein changes shape

• glucose moves across the CM(high to low)

• carrier protein returns to original shape

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ANIMATION – passive transport

16. Ion Channels• ion channels =

specific IMP

• ions are NOT soluble in lipids

• ion channel = passageway

• ions transported across the CM (high to low)

• some always open and some are gated

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16. Water• aquaporin = specific

IMP

• water is polar (hydrophilic)

• aquaporin = passageway

• water transported across the cell membrane (high to low)

• lots of aquaporin

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17. Active Transport• movement of molecules

from LOW concentration to HIGH concentration• ENERGY (ATP)

input needed• molecules MOVE

UP the concentration gradient

• TYPES of active transport• membrane pumps• endocytosis• exocytosis

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high

low

18. Sodium-Potassium Pump• active transport (nerve

cells)• 3 sodium (Na+) ions

bind to IMP pump(cytosol side)

• IMP changes shape (ATP used), 3 Na+ ions LEAVE the cell

• 2 potassium (K+) ions bind to same IMP pump (extracellular side)

• IMP shape change (ATP), 2 K+ ions ENTER the cell

• ions PUMPED from low to high, requires energy (ATP)

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ANIMATION #1 – sodium-potassium pumpANIMATION #2 – sodium-potassium pump

19. Endocytosis• active transport

• cells ingest fluid, macromolecules, large particles

• part of the cell membrane used

• pouch formed around particle vesicle

• lysosomes digest (break down) vesicle contents

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ANIMATION – active transport

19. Pinocytosis (type of endocytosis)

• type of endocytosis

• active transport

• transport of solutes or fluids

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19. Phagocytosis• type of endocytosis

• active transport

• transport of large particles / whole cells

• phagocytes (white blood cells)• ingest bacteria or

viruses

• fuse w/ lysosomes destroy bacteria or viruses

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ANIMATION – phagocyte

20. Exocytosis• reverse of endocytosis

• vesicles in cytoplasm fuse w/ cell membrane

• contents of vesicles released from cell

• ex. release of proteins from the cell

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Review Question #1• Draw the cell membrane.

• Which part of the cell membrane do/does…• oxygen pass through?

• water pass through?

• carbon dioxide pass through?

• ions pass through?

• Explain what…• selectively permeable means.

• fluid mosaic model means.

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Review Question #2• Draw a picture of passive transport using a person, a bike,

and a hill.

• Do molecules moves from high to low or low to high?

• Does the movement of molecules require energy? Please explain using the term concentration gradient in your explanation.

• Give two real examples of passive transport.

• Name two factors that can affect the rate of diffusion.

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Review Question #3• Draw a cell membrane that shows that water is in

equilibrium.

• Does water travel through the lipid bilayer or through a membrane protein when it crosses the cell membrane?

• If water is in equilibrium, do the molecules still move? Please explain.

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Review Question #4• Draw a before and after picture of a plant cell that’s placed

in a hypertonic environment. Does this plant cell experience a gain or loss of turgor pressure (plasmolysis)?

• Draw a before and after picture of a plant cell that’s placed in a hypotonic environment. Does this plant cell experience a gain or loss of turgor pressure (plasmolysis)?

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Review Question #5• Draw a before and after picture of an animal cell that’s

placed in a hypertonic environment. Does this animal cell experience cytolysis or crenation?

• Draw a before and after picture of an animal cell that’s placed in a hypotonic environment. Does this animal cell experience cytolysis or crenation?

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Review Question #6• Draw a paramecium in a hypotonic (freshwater)

environment. Draw an arrow to show how water moves.

• How does a paramecium deal with living in a hypotonic environment?

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Review Question #7• Explain how facilitated diffusion is a type of passive

transport. Use a diagram to help support your response.

• Draw and explain how carrier proteins work.

• Draw and explain how ion channels work.

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Review Question #8• Define active transport.

• Draw and explain how the sodium-potassium pump works.

• Draw and explain how endocytosis works.

• Draw and explain how exocytosis works.

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