LIPIDS
L2 BIOLOGY
Do Now: Key words to look up
 Phospholipids
 Selectively
permeable
 Hydrophilic
 Phospholipid
 Hydrophobic
bilayer
 Cholesterol
 Fluid mosaic
 Proteins (in cell
model
membrane)
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What are Lipids?

Lipids include substances like fats, oils
and waxes
 Typical

formula C51H98O6
What can you tell me about lipids from
looking at this formula?
Lipid Structure


one glycerol
three fatty acids
(also called a triglyceride)
GLYCEROL
FATTY ACIDS
LIPID=Glycerol +3 fatty
acids
Two Types of Fatty Acids

SATURATED
– The fatty acids are completely full of
hydrogen atoms (no double bonds!)

UNSATURATED
– There are one or more double bonds
Cont…

SATURATED FATS
– Usually solid, fully hydrogenated – animal
sources
Cont…

UNSATURATED FAT
– Usually a liquid; not fully hydrogenated plant sources
SATURATED OR
UNSATURATED?
Trans Fats: Bad in your diet!

Trans fats
–Unsaturated, but the double
bond between carbons is turned
so they are now SOLID at room
temperature
–Considered “bad” fats (we
create them artificially from
liquid oils)
–Margarine, creams in snacks
3 functions of Lipids



Major component of cell membranes.
Long term energy storage.
Protection.
1. What types of substances are
lipids?
2. What are the four parts that
make up a lipid?
3. What is the difference
between a saturated fat,
unsaturated fat, trans fat?
4. How are lipids like proteins?
5. How are lipids different from
proteins?
Cell Membranes:
Question: Can We live totally fat
Free ?
Every cell is enclosed by a
double layer of lipids: that
is the cell membrane
-Called a phospholipid
bi-layer
-What does this mean?
Cell (plasma) Membrane




Encloses the cell’s
contents
Function: Regulates
which particles
(nutrients, wastes)
can enter and exit the
cell.
Also is way cells
“communicate”
Selectively permeable
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A Phospholipid Bilayer
Phospholipids can form:
BILAYERS
-2 layers of phospholipids
with hydrophilic heads
(on outside) and
hydrophobic (fatty
acid) tails protected
inside.
The PHOSPHOLIPID
BILAYER is the basic
structure of membranes.
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Properties of Cell Membranes


Basic structure is Phospholipid Bilayer.
Phospholipids have HYDROPHOBIC (nonpolar) tails and HYDROPHILIC (polar)
heads.

The fatty acid tails of phospholipids can
be SATURATED (straight) or
UNSATURATED (bent)
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Plasma Membrane Structure

Building blocks are phospholipids…
– Lipid with a polar phosphate group attached to one
end.
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Properties of Cell
Membranes


Phospholipids act as a barrier to most
water soluble substances
BUT, Phospholipids are only PART of
the story…………
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Fluid mosaic model
Cell membranes also contain cholesterol and
proteins within the phospholipid bilayer.
This ‘model’ for the structure of the membrane is
called the: FLUID MOSAIC MODEL
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Why call it a Fluid Mosaic
Model?
FLUID- because phospholipids and some
proteins move around freely within the
layer, like it’s a liquid.
MOSAIC- because of the pattern
produced by scattered protein
molecules in the membrane when
viewed from above.
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Visualizing structure and
function

membrane animation
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Functions of Proteins/Cholesterol in
Cell Membrane

1. Proteins act as channels for substances to
move in or out of cell.

2. Some act as membrane enzymes in chemical
reactions.

3. Proteins help to stabilize the membrane.
Cholesterol stabilizes and prevents ions from
entering.

4. glycoproteins act as markers for cell
communication or receptors that hormones &
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other proteins can bind.
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Functions of components of cell
membranes
Use the following headings to produce a table summarizing
the functions of the different types of molecules found in
the cell membrane. Use your notes to find the
information.
Component
1.
Phospholipids
2.
Proteins
3.
Cholesterol
Description
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Function
25
Quick Quiz:
1. What is the main component of the
cell membrane?
2. a. What does the word “hydrophobic”
mean?
b. What does the word “hydrophilic”
mean?
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3. Name 1 function for proteins in the cell
membrane.
4. What is the function of cholesterol in the
cell membrane?
5 a. What do we call a protein with a
carbohydrate (sugar) attached?
b. Name 1 function for these molecules in
the membrane.
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