Biology Reference
In-Depth Information
CHAPTER
1
Introducti
on to Biological
Membranes
OUTLINE
A. What is a Biological Membrane?
1
Mitochondria
7
B. General Membrane Functions
3
D. Size of Domains
8
Can we see a membrane?
9
C. Eukaryote Cell Structure
4
Can we see a cell?
9
Endomembrane System
4
What can you see with a light
microscope?
Plasma Membrane
4
9
Nuclear Envelope (Membrane)
6
Endoplasmic Reticulum (ER)
7
E. Basic Composition of Membranes
10
Golgi Apparatus
7
Summary
11
Lysosome
7
Peroxisome
7
References
11
A. WHAT IS A BIOLOGICAL MEMBRANE?
The American Heritage Dictionary defines a membrane as 'a thin pliable layer of plant or
animal tissue covering or separating structures or organs.' The impression this description
leaves is one of the plastic wrap covering a hamburger. By this definition, membranes are
static, tough, impenetrable, and visible. Yet, nothing could be farther from the truth. The
entire concept of
dynamic
behavior is missing from this definition, yet dynamics is what
makes membranes both essential for life and so difficult to study.
If we could somehow instantaneously freeze a membrane and learn the composition and
location of each of the countless numbers of molecules comprising the membrane, and then
instantly return the membrane back to its original unfrozen state for a microsecond before
re-freezing, we would find that the membrane had substantially changed while unfrozen.
Although the molecular composition would remain the same over this short time, the
