An Introduction to Biological Membranes

Composition, Structure and Function

William Stillwell

• Publisher: Elsevier Science
• Year: 2016
• ISBN:
  9780444637901
• Edition: 2
• Topic: Scienze biologiche
• Subtopic: Biofisica

Introduction to Biological Membranes: Composition, Structure and Function, Second Edition is a greatly expanded revision of the first edition that integrates many aspects of complex biological membrane functions with their composition and structure. A single membrane is composed of hundreds of proteins and thousands of lipids, all in constant flux. Every aspect of membrane structural studies involves parameters that are very small and fast.

Both size and time ranges are so vast that multiple instrumentations must be employed, often simultaneously. As a result, a variety of highly specialized and esoteric biochemical and biophysical methodologies are often utilized. This book addresses the salient features of membranes at the molecular level, offering cohesive, foundational information for advanced undergraduate students, graduate students, biochemists, and membranologists who seek a broad overview of membrane science.

• Significantly expanded coverage on function, composition, and structure
• Brings together complex aspects of membrane research in a universally understandable manner
• Features profiles of membrane pioneers detailing how contemporary studies originated
• Includes a timeline of important discoveries related to membrane science

I

Membrane Composition and Structure

Outline

Chapter 1. Introduction to Biological Membranes

Chapter 2. Membrane History

Chapter 3. Water and the Hydrophobic Effect

Chapter 4. Membrane Lipids: Fatty Acids

Chapter 5. Membrane Polar Lipids

Chapter 6. Membrane Proteins

Chapter 7. Membrane Sugars

Chapter 8. From Lipid Bilayers to Lipid Rafts

Chapter 9. Basic Membrane Properties of the Fluid Mosaic Model

Chapter 10. Lipid Membrane Properties

Chapter 11. Long-Range Membrane Properties

Chapter 12. Membrane Isolation Methods

Chapter 13. Membrane Reconstitution

Chapter 1

Introduction to Biological Membranes

Abstract

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 static―like plastic wrap covering a package of hamburger. By this definition, membranes are tough, impenetrable, and visible. Nothing can be further 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. Dynamic is characterized by “constant change, activity, or progress.”

Keywords

Biological membrane; Cells; Cell contents; Cellular activities; Extracellular environment; Membranes

Outline

1. What Is a Biological Membrane?

2. General Membrane Functions

3. Eukaryote Cell Structure

3.1 Endomembrane System

3.2 Plasma Membrane

3.3 Cytoskeleton

3.4 Nuclear Envelope (Membrane)

3.5 Endoplasmic Reticulum

3.6 Golgi Apparatus

3.7 Lysosome

3.8 Peroxisome

3.9 Mitochondria

4. Size of Domains

4.1 Can We See a Membrane?

4.2 Can We See a Cell?

4.3 What Can Be Seen With a Light Microscope?

4.4 What Can Be Seen With an Electron Microscope?

5. Basic Composition of Membranes

6. Summary

References

1. 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 static―like plastic wrap covering a package of hamburger. By this definition, membranes are tough, impenetrable, and visible. Nothing can be further 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. Dynamic is characterized by “constant change, activity, or progress.”

If we could somehow instantaneously freeze a membrane and learn the composition and location of each of the countless numbers of molecules composing the membrane and then instantly return the membrane back to its original unfrozen state for a microsecond before refreezing, we would find that the membrane had substantially changed while unfrozen. Although the total molecular composition would remain the same, the molecular locations and interrelationships would have been altered. Therefore, membranes must have both static and dynamic components. While “static” describes what is there, “dynamics” describes how the components interact to generate biological function. The first half of this book focuses on static membrane composition and structure, while the second half concerns dynamic membrane functions.

Every cell in the human body is a tightly packed package of countless membranes. The human body is composed of approximately 63 trillion cells (6.3 × 10¹³ cells), each of which is very small. For example, a typical liver cell would have to be five times larger to be seen as a speck by someone with excellent vision (it is microscopic). Each liver cell has countless numbers of internal membranes. If you could somehow open a single liver cell, remove all of the internal membranes, and sew them together into a planar quilt, the quilt would cover about 840 acres, the size of New York City's Central Park! And all of that is from one cell. Therefore, there is sufficient membrane area in a human body to cover the earth millions of times over.

All life on Earth is far more similar than it is different. Living organisms share a number of essential biochemical properties, collectively termed the “thread of life.” Included in these essential properties is ownership of a surrounding plasma membrane (PM) that separates the cell's interior from its external environment. It is likely that all living things inhabiting planet Earth today arose from a single common ancestor more than 3.5 billion years ago. The first cell probably contained minimally a primitive catalyst (a pre-protein), a primitive information storage system (a pre–nucleic acid), a source of carbon (perhaps a primitive carbohydrate), and a primitive energy-transducing system, and this mixture had to be surrounded by a primitive PM that was likely made of polar lipids. Membranes were therefore an essential component of every cell that is alive today or has ever been alive. If life is found elsewhere in the universe, it would likely be surrounded by some type of PM.

With 3.5 billion years of biological evolution, the complexity of membranes in cells has greatly expanded from that of a simple surrounding PM to where they now occupy a large portion of a eukaryote's interior space. An electron microscopic picture of a “typical” eukaryotic (liver) cell is shown in Fig. 1.1 [1]. It is evident from the complexity of this micrograph that identifying, isolating, and studying membranes will be a difficult task.

2. General Membrane Functions

It is now generally agreed that biological membranes are probably involved somehow in all cellular activities. The most obvious function of any membrane is separating two aqueous compartments. For the PM, this involves separation of the cell contents from the very different extracellular environment. Membranes are therefore responsible for containment, ultimately delineating the cell. Separation, however, cannot be absolute as the cell must be able to take up essential nutrients, gases, and solute...