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Chapter 4: General Features of Cells

Page history last edited by Derek Weber 9 years, 9 months ago


Learning Objectives 

  • Explain the cell theory.
  • Describe various microscopic techniques, emphasizing differences in resolution and contrast.
  • Describe the factors that limit cell size.
  • Compare and contrast basic cell structure between prokaryotes and eukaryotes.
  • Categorize structural and functional similarities in cells.
  • Describe the organization of prokaryotic cells.
  • Compare the organization of eukaryotic and prokaryotic cells.
  • Discuss the role of the nucleus in eukaryotic cells.
  • Describe the role of ribosomes in protein synthesis.
  • Identify the different parts of the endomembrane system.
  • Contrast the different functions of internal membranes and compartments.
  • Evaluate the importance of each step in the protein processing pathway.
  • Trace the fates of A) a ribosomal protein, and B) a secreted protein.
  • Define the term semiautonomous, and outline the general functions of organelles that fall into this category.
  • Describe the structure of mitochondria and chloroplasts.
  • Compare the function of mitochondria and chloroplasts.
  • Explain the probable origin of mitochondria and chloroplasts.


Chapter Summary

All life is composed of cells, individually or as components of multicellular organisms. With certain exceptions, cells are very small. Substances diffuse more rapidly in a small cell, enhancing both its metabolism and its communication with other cells and with its environment. As a cell’s size increases, its volume increases at a much greater rate than its surface area. A cell’s survival depends on its surface, where all molecules enter and exit. If there is too little surface to support the workings of the interior, the cell will die.

 

Many of the structural differences between prokaryotes and eukaryotes are visible at the level of the light microscope; the presence of the nucleus in eukaryotes, for example. The nuclear material in prokaryotes is a single, circular strand of DNA, unencumbered by either proteins or a surrounding membrane and is difficult to see at the same scale. Observation with an electron microscope reveals details about the cytoskeleton and internal membrane systems of the eukaryotes, both absent in prokaryotes.  Different kinds of microscopes and different staining procedures can be used to obtain a desired image.

 

On a biochemical level, all of the reactions of a prokaryote, including those associated with ribosomes, occur openly in its cytoplasm, bounded only by invaginations of the plasma membrane. The reactions in a eukaryote are compartmentalized by the endoplasmic reticulum (ER) and by various membrane-bound organelles. Among these organelles are the nucleus, the Golgi apparatus, lysosomes, and microbodies (peroxisomes and glyoxysomes). The smooth and rough ER differ in appearance and function.

 

Rough endoplasmic reticulum possesses ribosomes while smooth endoplasmic reticulum lacks them. Various chemical products are synthesized on the rough endoplasmic reticulum, channeled into the Golgi bodies, and packaged into microbodies and lysosomes. Smooth ER contains embedded enzymes and is involved in carbohydrate and lipid synthesis and detoxification.

 

Some eukaryotic organelles contain DNA, notable among these are the cell’s powerhouses, the mitochondria and the chloroplasts.  Plant, fungi, and some protists have special adaptations that are lacking in other cells. Plant cells have a large central vacuole which serves as a storage compartment and helps increase the cell’s surface-to-volume ratio. Plants cells and some protists have strong, rigid cell walls composed of cellulose whereas fungi have chitin in their cell walls.  Animal cells lack cell walls but have their cytoskeleton linked to the extracellular matrix.

 

PowerPoint Presentation

Chapter 4 PowerPoint

 

Virtual Lectures

Section 4.1:  Microscopy

Section 4.2:  Overview of Cell Structure

Section 4.4 and 4.6:  The Endomembrane System and Protein Sorting

 

Animations

1.  Limitations on Cell Size

2.  Common Features of all Cells

3.  Example of a Prokaryotic Cell: Bacteria

4.  General Features of Eukaryotic Cells

5.  Nuclear Envelope

6.  Compartmentalization of the Eukaryotic Cell: The Endomembrane System

7.  Protein Secretion from the Cell

8.  Cytoskeleton Proteins: Flagella and Motor Proteins

 

 Also view Chapter 5: Membrane Structure, Synthesis, and Transport for animations about protein trafficking within the cell.

 

Miscellaneous

This is a video from the Virtual Cell project funded by the National Science Foundation.  For more information, see http://vcell.ndsu.nodak.edu/animations.

 

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Journal Article:

http://edrv.endojournals.org/content/26/4/479.full.pdf+html 

 

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