1. The building blocks of life
Cells
Chapter 3
Cell Organelles (Plasma Membrane (Phospholipid) Slide 46-67
The building blocks of life

2. Biology, 9th ed,Sylvia Mader
Chapter 04
Plasma Membrane
Cell Structure and Function
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
protein molecules
phospholipid bilayer

3. Cell/Plasma Membrane
Surrounds all types of cells. Prokaryote & Eukaryotes
In a plant cell, it lies beneath the cell wall
In animal cells, it is the outer boundary (made of cholesterol)
Provides cell with
Protection and supports the cell
Control of movement of materials in/out of cell
Maintains condition of cell

4. Cytoplasmic Membrane
Surrounds the cell and decides what comes in and out
Semi-permeable: allows nutrients in and waste products out
Made of a phospholipid bilayer
Also called Plasma Membrane

5. Cytoplasmic Membrane Factory Part: Found in: Gates or Doors
Plant cells
Animal cells
Prokaryotic cells

6. Cell membrane Encloses the cell contents, security gate
phospholipid bilayer with embedded proteins
Phospholipid bilayer
Membrane proteins

7. Cytoplasmic Membrane The cytoplasmic/plasma/cell membrane
In eukaryotic cells, as in prokaryotes
Fluid phospholipid bilayer embedded with proteins and glycoproteins.
Phospholipid bilayer is arranged so that the polar ends of the molecules (the phosphate and glycerol portion of the phospholipid that is soluble in water) form the outermost and innermost surface of the membrane while the non-polar ends (the fatty acid portions of the phospholipids that are insoluble in water) form the center of the membrane

8. Cytoplasmic Membrane The cytoplasmic/plasma/cell membrane
Contains glycolipids as well as complex lipids called sterols
Cholesterol molecules found in animal cell membranes not found in prokaryotic membranes(except for some mycoplasmas
Sterols make the membrane less permeable to most biological molecules
Help to stabilize the membrane
Probably add rigidity to the membranes aiding in the ability of eukaryotic cells lacking a cell wall to resist osmotic lysis.
Proteins and glycoproteins in the cytoplasmic membrane are quite diverse and function as:
a. channel proteins to form pores for the free transport of small molecules and ions across the membrane
b. carrier proteins for facilitated diffusion and active transport of molecules and ions across the membrane
c. cell recognition proteins that identifies a particular cell
d. receptor proteins that bind specific molecules such as hormones and cytokines
e. enzymatic proteins that catalyze specific chemical reactions.

9. Cellular membranes are fluid mosaics of lipids and proteins
Phospholipids are the most abundant lipid in the plasma membrane
Phospholipids are amphipathic molecules, containing hydrophobic and hydrophilic regions (having two different affinities, as a polar end that is attracted to water and a nonpolar end that is repelled by it.)
The fluid mosaic model states that a membrane is a fluid structure with a “mosaic” of various proteins embedded in it
For the Cell Biology Video Structure of the Cell Membrane, go to Animation and Video Files.

10. Plasma Membrane Contains cell contents
Double layer of phospholipids & proteins

11. Phospholipids Polar Interacts with water Hydrophylic head
Hydrophobic tail
Interacts with water

12. AP1: BIOCHEMISTRY: PHOSPHOLIPIDS

13. BCLN - Phospholipids - Biology

14. Cell/Plasma Membrane

15. The Plasma Membrane
In animal cells, the plasma membrane has four principal components:
1. A phospholipid bilayer.
Molecules of cholesterol interspersed within the bilayer.
Proteins that are embedded in or that lie on the bilayer.
Short carbohydrate chains on the cell surface, collectively called the glycocalyx, that function in cell adhesion and as binding sites on proteins.

16. The Plasma Membrane Figure 5.1 phospholipids cholesterol proteins
glycocalyx
cell
exterior
cell
interior
cytoskeleton
peripheral
protein
integral
protein
Phospholipid bilayer:
a double layer of
phospholipid
molecules whose
hydrophilic “heads”
face outward, and
whose hydrophobic
“tails” point inward,
toward each other.
Cholesterol molecules
that act as a patching
substance and that
help the cell maintain
an optimal level of
fluidity.
Proteins, which are
integral, meaning
bound to the
hydrophobic interior of
the membrane, or
peripheral, meaning not
bound in this way.
Glycocalyx: sugar
chains that attach to
proteins and
phospholipids, serving
as protein binding sites
and as cell lubrication
and adhesion
molecules.
Figure 5.1

17. The Phospholipid Bilayer
Phospholipids are molecules composed of two fatty acid chains linked to a charged phosphate group.
The fatty acid chains are hydrophobic, meaning they avoid water, while the phosphate group is hydrophilic, meaning it readily bonds with water.

18. The Phospholipid Bilayer
Such phospholipids arrange themselves into bilayers—two layers of phospholipids in which the fatty acid “tails” of each layer point inward (avoiding water), while the phosphate “heads” point outward (bonding with it).

19. The Phospholipid Bilayer
Phospholipids take on this configuration in the plasma membrane because a watery environment lies on either side of the membrane.

20. The Phospholipid Bilayer
As temperatures cool, membranes switch from a fluid state to a solid state
The temperature at which a membrane solidifies depends on the types of lipids
Membranes rich in unsaturated fatty acids are more fluid than those rich in saturated fatty acids
Membranes must be fluid to work properly; they are usually about as fluid as salad oil
The steroid cholesterol has different effects on membrane fluidity at different temperatures
At warm temperatures (such as 37°C), cholesterol restrains movement of phospholipids
At cool temperatures, it maintains fluidity by preventing tight packing

21. Unsaturated hydrocarbon tails Saturated hydrocarbon tails
Figure 7.8
Fluid
Viscous
Figure 7.8 Factors that affect membrane fluidity.
Unsaturated hydrocarbon tails
Saturated hydrocarbon tails
(a) Unsaturated versus saturated hydrocarbon tails
(b) Cholesterol within the animal cell membrane
Cholesterol 21

22. Cell membranes are made of PHOSPHOLIPIDs
HYDROPHILIC heads (water liking) -Attracted to the water
called POLAR
HYDROPHOBIC tails (water fearing) -Not attracted to the water
called NON-POLAR
A Phospholipid