• Honors Biology Cell Membranes and Transport
Worksheet – Answers
• Composition of the Cell Membrane and Functions
• The cell membrane is also called the PLASMA
membrane and is made of a phospholipid BILAYER. The
phospholipids have a hydrophilic (water attracting)
HEADS and two hydrophobic (water repelling) TAILS.
The head of a phospholipid is made of an alcohol and
PHOSPHATE group, while the tails are chains of
HYDROCARBONS or FATTY ACIDS. Phospholipids can
move AROUND/FLUIDLY/LATERALLY and can allow
water and other SMALL AND NONPOLAR molecules to
pass through into or out of the cell. This is known as
simple DIFFUSION because it does not require ENERGY
and the water or molecules are moving DOWN/WITH
the concentration gradient.
Hydrophilic
Hydrophobic
• Embedded in the phospholipid bilayer are
PROTEINS that also aid in diffusion and in cell
recognition. Proteins called INTEGRAL proteins go
all the way through the bilayer, while PERIPHERAL
proteins are only on one side. Integral proteins are
also called CARRIER or TRANSPORT proteins
because they allow molecules to pass through the
membrane. Large molecules like AMINO ACIDS or
carbohydrates use proteins to help move across cell
membranes. Some of the membrane proteins have
CARBOHYDRATES attached to help cells in recognize
each other and certain molecules.
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A = Phospholipid Bilayer
B = Integral protein
F = Fatty acid tails
G = Phosphate heads
• G = Attracts water
• I = Helps maintain etc.
• C,E,H = Involved in etc.
H = Peripheral protein
I = Cholesterol
C = Glycoprotein
E = Glycolipids
F = Repels water
A,F,G = Make up bilayer
B = Help transport etc.
• Osmosis and Tonicity
• Osmosis is the diffusion of water across a semipermeable
membrane.
• With/Down
• Isotonic = Same concentration as the other side
• Hypertonic = Higher concentration than the other side
• Hypotonic = Lower concentration than the other side
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C - solution with a lower solute concentration
A - solution in which the solute concentration is the same
A or C - condition plant cells require
A - condition that animal cells require
C - red blood cell bursts (cytolysis)
B - plant cell loses turgor pressure (Plasmolysis)
B - solution with a higher solute concentration
C - plant cell with good turgor pressure
C - solution with a high water concentration
• Labeling pictures left to right, top row first
• Hypotonic
Isotonic
Hypertonic
• Hypotonic
Isotonic
Hypertonic
• Labeling beaker solutions (Isotonic, hypertonic, or
hypotonic) and water direction (Out of cell, into cell, or in
and out of cell equally) from left to right, top row first
• Iso/Equally
Hypo/In
Hyper/Out
Hyper/Out
• Hypo/In
Hypo/In
Hypo/In
Iso/Equal
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1. Out
2. Into
3. Osmosis
4. Diffusion
5. higher; lower
6. Arrow should go right to left
7. Arrow should go left to right
8. Diffusion
9. Osmosis
10. From left to right, indicating arrow direction and
whether the cell will expand or contract:
• In/Expand
Equal/Neither
Out/Contract
Out/Contract