Movement Across the Cell Membrane
YOU NEED TO PHYSICALLY DRAW/WRITE OUT EACH CONCEPT WHILE EXPLAINING. DO NOT LET
STUDENTS COPY WHILE YOU WRITE. AFTER YOU WRITE A SECTION, ASK QUESTIONS AND TAKE
QUESTIONS, THEN ALLOW STUDENTS TIME TO COPY INTO THEIR OWN NOTEBOOK.
-Start while gummy bears are in solution•
WATCH GUMMY BEAR YOUTUBE https://www.youtube.com/watch?v=HqKlLm2MjkI
1. Cell membrane= semipermeable barrier (allows some substances in and keeps others out)
Draw cell membrane
A. Allows materials to be
a. Excluded from cells
b. Separated from outside of the cell
c. Concentrated inside of the cell
i. Concentration- amount of solute/component in a given area/volume
High Concentration
Low Concentration
Homeostasis
Homeostasis- “same state”; constant internal environment
The plasma membrane’s goal is to achieve homeostasis.
Hypotonic- more water
Hypertonic- more solute (more sugar=you get more hyper)
Isotonic- equal
Questions: (make your students draw pictures like above if they don’t get it)
-What will happen to the cell in the following situations?
1. Cell 75% solvent; environment 25% solvent
2. Cell 50% solvent; environment 50% solvent
3. Cell 15% solvent; environment 85% solvent
-Weigh gummy bears and figure out how to make them shrink (hypertonic environment)
-record in notebook
How the Plasma membrane transports materials/ achieves homeostasis
A. Simple Diffusion
No E; Conc
B. Osmosis
Gradient
C. Facilitated Diffusion (Passive Transport)
D. Active Transport
Requires E/ATP
E. Movement via vesicles
A. Simple Diffusion
a. Movement of molecules from an area of high concentration to an area of low
concentration
b. Molecules that can dissolve in lipids (fatty acid tails) like CO2 and O2
c. The difference in the concentration of molecules across a distance is called a
concentration gradient:
i. Movement from areas of high concentration to low concentration.
ii. Driven by kinetic energy (movement)
iii. Eventually an equilibrium is reached (same concentration throughout)
High ---------------------------------- low
Until EQUILIBRIUM
Show PHET simulation: Diffusion
B. Osmosis
a. https://www.youtube.com/watch?v=7-QJ-UUX0iY
b. Water molecules move from areas of high concentration to areas of low concentration
i. Hypotonic
ii. Hypertonic
iii. Isotonic
i. Hypotonic outside of cell: Water diffuses into the cell; more solute inside of the cell
ii. Hypertonic outside of cell: water moves out of the cell; more solute outside of the cell
iii. Isotonic outside of cell: concentrations of solute are equal inside and outside of cell
Adaptations for osmosis:
1. Paramecium: contractile vacuole
a. https://www.youtube.com/watch?v=iG6Dd3COug4
2. Plants: turgor pressure V plasmolysis
a. https://www.youtube.com/watch?v=fNyYuVarTIQ
3. RBC: cytolysis: bursting
a. https://www.youtube.com/watch?v=psUt9zrACL8
C. Facilitated Diffusion
a. For molecules that cannot move across the plasma membrane
b. Assisted by carrier proteins/integral proteins
c. High concentration to low concentration
d. EX: glucose
e. Ion Channel: Na+ Cl-
D. Active Transport:
a. Cell membrane pumps that require ENERGY!
b. Ex: Sodium Potassium Pump
c. https://www.youtube.com/watch?v=P-imDC1txWw
E. Movement in vesicles
a. Endocytosis: cells ingest macromolecules
i. Pinocytosis: solutes or fluids
ii. Phagocytosis: large particles
1. https://www.youtube.com/watch?v=CEOV-SFTlpY
2. https://www.youtube.com/watch?v=pvOz4V699gk
b. Exocytosis: substances are released from the cell
i. https://www.youtube.com/watch?v=U9pvm_4-bHg
Review:
Driven by
Types
Molecules
Passive
Concentration gradient
Diffusion, osmosis, facilitated
diffusion
Non-polar, small, water, CO2,
Active
ATP
Cell membrane pumps,
endocytosis, exocytosis
NaCl pump; bacteria