Download The Cell Membrane

Unit 2: Cells
Chapter 7-3
Cell Biology standard 1a
Students know cells are enclosed within semipermeable
membranes that regulate their interaction with their
surroundings.
Learning Goals:
•1. Describe the job/function of the cell membrane
•2. Explain what semi-permeable means.
•3. Describe the structure of the cell membrane.
•4. Describe the 3 types of movement across the cell
membrane. Include whether energy is required and which
direction the molecules move.

Cell Membranes surround ALL cells!

It controls what enters/leaves the cell

SEMIPERMEABLE – means it allows some
things through but not others



Made up of a Phospholipid bilayer
Polar heads “love” water (hydrophilic)
Nonpolar tails “fear” water (hydrophobic)


“Fluid mosaic model”
– describes the
structure of the cell
membrane.
Proteins float around
in the membrane like
icebergs in the ocean
Which of the following is NOT true
about the cell membrane:




A.
B.
C.
D.
Surrounds all cells
Controls what enters and leaves the cell
Surrounds the nucleus
Is a phospholipid bilayer
The cell membrane is
semipermeable. This means:




A. All things can pass through
B. Some things are let in or out but not
everything
C. Everything is blocked
D. Only small molecules may pass through

Keeps things in or out

Molecules can enter/leave the cell 3 ways
1. Diffusion
2. Carrier-Facilitated (“helped”) diffusion
3. Active transport


ATP
No energy required
Molecules move from area of high
concentration to area of low concentration
 Concentration = # of molecules in an area
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Diffusion of water is called “osmosis”

No energy required
ATP

Molecules “helped” across by proteins from
high to low concentration

Energy required!
ATP
◦ ATP – the “battery” of the cell
◦ Breaking a bond in ATP releases energy
◦ Can “pump” molecules from low to high
concentration building them up in the cell
The diffusion of water is called:




A Osmosis
B. Transfusion
C. Water transport
D. Active transport
In diffusion molecules move:




A. From low to high’ no energy
B. From low to high; needs energy
C. From high to low; no energy
D. From high to low; needs energy
In carrier facilitated diffusion
molecules move:




A. From low to high’ no energy
B. From low to high; needs energy
C. From high to low with the help of a
protein; no energy
D. From high to low; needs energy
In active transport molecules
move:




A. From low to high’ no energy
B. From low to high; needs energy
C. From high to low; no energy
D. From high to low; needs energy
Learning Goals:
•1. Describe the job/function of the cell membrane
•2. Explain what semi-permeable means.
•3. Draw and label the structure of the cell membrane.
•4. Describe the 3 types of movement across the cell
membrane. Include whether energy is required and which
direction the molecules move.