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Chapter 1

Membrane Structure and
Membranous Organelles

CHAPTER OUTLINE
Introduction
1.1 Common properties and inheritance of cell membranes
1.2 The fluid-mosaic membrane model
1.3 Plasma membrane
1.4 Endoplasmic reticulum
1.5 Golgi apparatus
1.6 Exocytosis and endocytosis
1.7 Vacuoles
1.8 The nucleus
1.9 Peroxisomes
1.10 Plastids
1.11 Mitochondria

L. Andrew Staehelin
Eldon H. Newcomb

 

 

 

Cells, the basic units of life, require membranes for their existence. Foremost among these is the plasma membrane, which defines each cell’s boundary and helps create and maintain electrochemically distinct environments within and outside the cell. Other membranes enclose eukaryotic organelles such as the nucleus, chloroplasts, and mitochondria. Membranes also form internal compartments, such as the endoplasmic reticulum (ER) in the cytoplasm and thylakoids in the chloroplast (Fig. 1.1).
      The principal function of membranes is to serve as a barrier to the diffusion of most water-soluble molecules. These barriers delimit compartments wherein the chemical composition can differ from the surroundings and can be optimized for a particular activity. Membranes also serve as scaffolding for certain proteins. As membrane components, proteins perform a wide array of functions: transporting molecules and transmitting signals across the membrane, processing lipids enzymatically, assembling glycoproteins and polysaccharides, and providing mechanical links between cytosolic and cell wall compounds.
      This chapter is divided into two parts. The first is devoted to the general features and molecular organization of membranes. The second provides an introduction to the architecture and functions of the different membranous organelles of plant cells. Many later chapters of this text focus on metabolic events that involve these organelles.


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