Molecular Cell Biology

Harvey Lodish, Arnold Berk, Chris A. Kaiser

ISBN #9781464183393

8th Edition

406 Questions

12,309 Students Helped

Homework Questions

Summary

Learning Objectives

Key Concepts

Example Problems

Explanations

Common Mistakes

Summary

Stem cells are characterized by the abilities to self-renew and differentiate into various cell types. Depending on their potency, they can be totipotent, pluripotent, or multipotent. Both plant and animal stem cells reside in specialized niches that provide key survival and regulatory signals. Reprogramming differentiated cells (as evidenced by nuclear transfer and iPS cell technology) shows the latent potential within somatic cells. In parallel, regulated cell death via apoptosis—controlled by conserved proteins such as caspases, Bcl-2 family members, and IAPs—ensures that damaged or excess cells are eliminated in an orderly, non-inflammatory manner. Understanding these processes is critical for applications in regenerative medicine and cancer therapy.

Learning Objectives

Key Concepts

CONCEPT

DEFINITION

Biomembrane Structure

The organized, selectively permeable barrier of the cell composed primarily of amphipathic phospholipids, cholesterol, and proteins, which self?assembles into a lipid bilayer. These structures regulate membrane fluidity, thickness, and the assembly and function of integral and peripheral membrane proteins.

Example Problems

Example 1

What two properties define a stem cell? Distinguish between a totipotent stem cell, a pluripotent stem cell, and a precursor (progenitor) cell.

Example 2

Where are stem cells located in plants? Where are stem cells located in adult animals? How does the concept of a stem cell differ between animal and plant systems?

Example 3

In $1997,$ Dolly the sheep was cloned by a technique called somatic-cell nuclear transfer (or nuclear-transfer cloning). A nucleus from an adult mammary cell was transferred into an egg from which the nucleus had been removed. The egg was allowed to divide several times in culture, then the embryo was transferred to a surrogate mother who gave birth to Dolly. Dolly died in 2003 after mating and giving birth herself to viable offspring. What does the creation of Dolly tell us about the potential of nuclear material derived from a fully differentiated adult cell? Does the creation of Dolly tell us anything about the potential of an intact, fully differentiated adult cell?

Example 4

Identify whether the following contain totipotent, pluripotent, or multipotent cells: (a) inner cell mass, (b) morula, (c) eight-cell embryo, (d) trophectoderm.

Example 5

True or false: Differentiated somatic cells have the capacity to become reprogrammed to become other cell types. Provide one line of evidence discussed in the chapter that corroborates your response.