Do Now
• Handout 7.2 The Plasma Membrane
Before you read handout
• Homework
– Eukaryotic Cell Structure handout
– Organelle quiz on Friday
• Know the structures and functions
• Be able to label a diagram
– Test next Tuesday on Chapter 7
Lipids and Cell Membrane
Lipids (a.k.a. Fats)
• Lipids are NOT soluble in water.
– Lipids are non-polar.
• Lipids store large amounts of energy.
• The monomers are called fatty acids.
• Lipids make up most of the cell membrane.
The cell membrane is made of special lipids called
Polar heads are hydrophilic – “water loving”
Non-polar tails are hydrophobic – “water
The polarity determines the arrangement of the
Phospholipids form two layers – called lipid
Polar heads face outward (water outside and
inside the cell)
Non-polar tails face inward (creates barrier to
protect the cell)
Cell Membrane Structure
• The cell membrane also contains other fats,
proteins, and carbohydrates.
Cell Membrane Proteins
1. Integral Proteins
Proteins that penetrate completely through
the membrane (inside)
2. Peripheral Proteins
Embedded but not all the way
Located on the outside surface and function to
help transport different substances into and out
of the cell.
fluid mosaic model
Cell Membrane Functions
• Controls what enters and exits the cell.
– Selectively Permeable - only lets certain molecules into
and out of the cell
• Maintains cell’s shape.
• Connects each cell to other cells near it.
• Can allow movement of the cell
– parts can move around each other, called the fluid
mosaic model.
fluid mosaic model
Cell Membrane Model Answers
• 1. Phospholipid molecules move freely
throughout the membrane in a fluid
motion, while the overall structure of the
membrane remains unchanged.
• 2. Phospholipid has two distinct parts
– Polar, hydrophilic head form the inside and
outside surfaces of the membrane
– 2 Nonpolar, hydrophobic tails form the interior
core of the membrane
Membrane Model Answers
• 3. Selective permeability refers to the fact
that the membrane functions as a
gatekeeper, monitoring and facilitating the
entry and exit of molecules into and out of
the cell.
• 4. Channels or pumps that actively move
waste out of cell and move nutrients into
the cell.
• Complete The Plasma Membrane handout
pg 72-73
• Turn in as you walk out

Lipids and Cell Membrane Structure