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Unit 1:
Ch. 1
Ch. 2
Ch. 3
Interlude A
Unit 2:
Ch. 4
Ch. 5
Ch. 6
Ch. 7
Ch. 8
Ch. 9
Interlude B
Unit 3:
Ch. 10
Ch. 11
Ch. 12
Ch. 13
Ch. 14
Ch. 15
Interlude C
Unit 4:
Ch. 16
Ch. 17
Ch. 18
Ch. 19
Interlude D
Unit 5:
Ch. 20
Ch. 21
Ch. 22
Ch. 23
Ch. 24
Ch. 25
Ch. 26
Ch. 27
Ch. 28
Ch. 29
Ch. 30
Interlude E
Unit 6:
Ch. 31
Ch. 32
Interlude F
Unit 7:
Ch. 33
Ch. 34
Ch. 35
Ch. 36
Ch. 37
Ch. 38
Interlude G

» Getting Started » A Guide to the Reading » Tying it all together

Getting Started

Below are a few questions to consider prior to reading Chapter 5. These questions will help guide your exploration and assist you in identifying some of the key concepts presented in this chapter.

  1. What provides the propulsive force that pushes the bacterium Listeria as it travels through an infected cell?
  2. Who was Robert Hooke and what was he the first to observe?
  3. What is the "fluid mosaic model"?
  4. What are the "little organs" of the cell called?
  5. If the cell were considered as a tiny factory, which structure would serve as the shipping department? Which structure would serve as the power plant?
  6. What are the three main components of the cytoskeleton and what are their functions?
  7. In a cell that is capable of swimming through water, what tiny structures would be analogous to the oars of a rowboat?

A Guide to the Reading

When exploring the content in Chapter 5 for the first time, the following concepts typically give students the most difficulty. For each concept, one or more references have been identified which may help you gain a better understanding of these potentially problematic areas.

Fluid Mosaic Model

The plasma membrane serves as the outer boundary of the cell. As discussed in Chapter 4, membranes are composed primarily of phospholipids arranged in a bilayer. Unfortunately, this bilayer arrangement restricts the movement of many molecules across the membrane. In order for the cell to import nutrients, export wastes, and communicate with its surroundings through the use of signaling molecules, it employs the services of special membrane proteins which are embedded in the phospholipid bilayer. These proteins perform specialized functions, such as the transport of larger molecules across the membrane. It is important to note that the proteins embedded in the plasma membrane are typically free to move laterally within the plane of the membrane. Since the membrane is composed of a mosaic of protein and phospholipids and the proteins are free to move fluidly, the plasma membrane of cells is often referred to as a fluid mosaic. This characteristic is important for the cell’s ability to move and to communicate with its environment.

For more information on this concept, be sure to focus on:

  • Section 5.2, The Plasma Membrane: Separating Cells from Their Environment
  • Figure 5.1, Proteins are Embedded in the Plasma Membrane

Nuclear Envelope

As discussed in the chapter, the nucleus serves as the "administrative center" of the cell and is the central repository for genetic information in eukaryotes. It is a relatively large, distinct structure which houses the cell’s DNA. In order to keep nuclear contents and the cytosol separate, the nucleus is enclosed by not one, but two membranes – referred to as the nuclear envelope. The nuclear envelope contains numerous holes or "pores" which provide a passageway for particular molecules to enter or exit the nucleus. These nuclear pores are very similar to the channels which appear within the plasma membrane, regulating the passage of larger molecules into or out of the cell.

For more information on this concept, be sure to focus on:

  • In Section 5.4, The nucleus is the repository for genetic material
  • Figure 5.3, The Nucleus

Movement Between Compartments

The cytosol of the eukaryotic cell contains numerous organelles which work together to carry out the activities of the cell. Part of this includes the production and export of proteins. This process begins at the "factory floor" of the cell, the endoplasmic reticulum. Tiny structures called ribosomes attached to the surface of the endoplasmic reticulum function to produce proteins directly inside the membrane enclosed ER (the lumen). In order to complete their journey, these proteins must escape the confines of the ER for processing and sorting in a different organelle – the Golgi apparatus. But how do they get there? The answer is through the use of tiny, membrane-bound transport structures called vesicles. Vesicles are produced when parts of the ER begin to "bud" off of the organelle. Contents of the lumen of the ER, including the proteins destined for the Golgi apparatus, become trapped inside these buds, which finally break off, forming a transport vesicle. The transport vesicle then makes its way through the cytosol until it fuses with a nearby Golgi apparatus, dumping the trapped contents (including the protein) inside the Golgi. Once the proteins are processed inside the Golgi, they can then be transported by another vesicle to their final destination. The budding and fusion of transport vesicles is made possible by the fluid nature of the bounding membranes. Since the inner portion of the phospholipid bilayers is hydrophobic, they will have a tendency to fuse together, just like two bubbles floating in the air or two droplets of oil floating on the surface of water might fuse together.

For more information on this concept, be sure to focus on:

  • In Section 5.4, The endoplasmic reticulum is the site of manufacture for lipids and many proteins
  • Figure 5.5, How Vesicles Move Proteins and Lipids from One Compartment to Another

Cell Motility

The cytoskeleton of the cell serves to provide both structure and movement to a cell. It consists of three distinct types of filaments: microtubules, intermediate filaments, and microfilaments. Microtubules are the largest of these structures. In eukaryotes, they facilitate cell motility in two ways. The first way involves the creation of a tiny system of "tracks", analogous to a subway system, starting at the center of the cell (adjacent to the nucleus) and branching outward toward the plasma membrane. These tiny tracks are used by structures such as transport vesicles to crawl along to reach their final destination. Microtubules also provide the rigidity and flexibility necessary to produce tiny rowing (cilia) or beating (flagella) structures which serve to propel cells through a fluid medium.

In contrast, microfilaments are the smallest of the cytoskeletal structures. In eukaryotes, they facilitate cell movement by constantly adjusting their length and rearranging their alignment at the cell surface. By growing and realigning, the force of the microfilaments causes small protrusions, termed pseudopodia to emerge from the cell, allowing it to grab hold and crawl along a surface. Intermediate filaments are not believed to serve a motility function in cells, but rather provide the cell with structural support.

For more information on this concept, be sure to focus on:

  • In Section 5.5, Microtubules support movement inside the cell
  • In Section 5.5, Microfilaments are involved in cell movement
  • In Section 5.5, Cilia and flagella act like oars and propellers
  • Figure 5.11, Kinds of Filaments in the Cytoskeleton
  • Figure 5.12, Microfilaments allow Cell Movement
  • Figure 5.13, Eukaryotic Cilia and Flagella

Tying it all together

Several concepts presented in this chapter build upon concepts presented in previous chapters and are also revisited and discussed in greater detail in subsequent chapters, including:

Prokaryotes vs. Eukaryotes

  • Chapter 3 – in Section 3.1, Organisms can also be identified as prokaryotes and eukaryotes

Atomic Composition of Life

  • Chapter 4 – Section 4.1, Atoms Make Up the Physical World

Biological Membranes

  • Chapter 4 – in Section 4.5, Fatty acids store energy and form membranes

Cell Signaling and Communication

  • Chapter 6 – Section 6.6, Signaling Molecules in Cell Communication

Energy in Living Systems

  • Chapter 7 – Section 7.1, The Role of Energy in Living Systems
  • Chapter 8 – Section 8.3, Catabolism: Breaking Down Molecules for Energy


  • Chapter 8 – Section 8.2, Photosynthesis: Capturing Energy from Sunlight


  • Chapter 12 – Section 12.1, The Search for the Genetic Material

Protein Synthesis

  • Chapter 13 – Section 13.5, Translation: Information Flow from mRNA to Protein

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