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Essential Cell Biology has been carefully geared to introductory students, without any sacrifice of scientific rigor. The book's conceptual approach, in which the essential facts are presented in their biological context, is ideal for engaging and motivating students new to molecular and cell biology. The book is written especially for undergraduates in biological sciences, but its content can be easily understood and absorbed by advanced secondary school students who need a basic introduction to the essential topics in modern biology.
"...This new work is by the same exceptional team that wrote the acclaimed text, Molecular Biology of the Cell...explains cell biology at a level that is easy to grasp for students with a minimal knowledge of biology."
Muscle contraction is the most familiar and the best understood of animal cell movements. In vertebrates, running, walking, swimming, and flying all depend on the ability of skeletal muscle to contract strongly and move various bones. Involuntary movements such as heart pumping and gut peristalsis depend on cardiac muscle and smooth muscle, respectively, which are formed from muscle cells with a different structure from skeletal muscle, but which use actin and myosin in a similar way to contract.
The long fibers of skeletal muscle are huge single cells formed during development by the fusion of many separate smaller cells. The individual nuclei of the contributing cells are retained in the muscle fiber and lie just beneath the plasma membrane. The bulk of the cytoplasm is made up of myofibrils, the contractile elements of the muscle cell. These cylindrical structures are 1-2 gm in diameter and may be as long as the muscle cell itself (Figure 16-34A).
A myofibril consists of a chain of identical tiny contractile units, or sarcomeres. Each sarcomere is about 2.5 gm long, and in a chain, their regular pattern gives the vertebrate myofibril a striped, or striated, appearance (Figure 16-34B). Sarcomeres are highly organized assemblies of two types of filaments-actin filaments and filaments of musclespecific myosin-II. Myosin filaments (the thick filaments) are centrally positioned in each sarcomere, whereas the thinner actin filaments (the thin filaments) extend inward from each end of the sarcomere (where they are anchored by their plus ends to a structure known as the Z disc) and overlap the ends of the myosin filaments (Figure 16-35).
The contraction of a muscle cell is caused by a simultaneous shortening of all the sarcomeres, which in turn is caused by the actin filaments sliding past the myosin filaments with no change in the length of either type of filament (Figure 16-36). The sliding motion is generated by myosin heads that project from the sides of the myosin filament and interact with adjacent actin filaments. When a muscle is stimulated to contract, the myosin heads start to walk along the actin filament in repeated cycles of attachment and detachment; their combined action pulls the actin and myosin filaments past each other, causing the sarcomere to contract. After a contraction is completed, the myosin heads lose contact with the actin filaments completely, and the muscle relaxes.
During each cycle of attachment and detachment, a myosin head binds and hydrolyzes one molecule of ATP This is thought to cause a series of conformational changes in the myosin molecule that move the tip of the head by about 5 nanometers along the actin filament toward the plus end. This movement, repeated with each round of ATP hydrolysis, propels the myosin molecule unidirectionally along the actin filament (Figure 16-37). In so doing, the myosin heads pull against the actin filament, causing it to slide against the myosin filament. Each myosin filament has about 300 myosin heads; each myosin head can cycle about five times per second, sliding the myosin and actin filaments past one another at a speed of up to 15 ~tm per second. This speed is sufficient to take a sarcomere from a fully extended state (3 gym) to a fully contracted state (2 pm) in less than a tenth of a second. All of the sarcomeres of a muscle are coupled together and are triggered almost instantaneously by the system of signals described in the following section. Therefore, the entire muscle contracts extremely rapidly, usually within a tenth of a second.
|List of Topics|
|1||Introduction to Cells||1|
|2||Chemical Components of Cells||37|
|3||Energy, Catalysis, and Biosynthesis||77|
|4||How Cells Obtain Energy from Food||107|
|5||Protein Structure and Function||133|
|7||From DNA to Protein||211|
|8||Chromosomes and Gene Regulation||245|
|13||Energy Generation in Mitochondria and Chloroplasts||407|
|14||Intracellular Compartments and Transport||447|
|18||Cell-Cycle Control and Cell Death||571|
|Answers to Questions||A-1|
Posted February 18, 2003
Posted November 2, 2001
This is book is written in simple language and thats great. But it does not cover all the concepts that are 'Essential' for cell biology. Like the section on development is so poorly dealt that it does not even go to the extent of explaining the fusion of sperm and egg which is the basis of life. I think the book needs to be revised and details need to be added to give a complete picture of the essentials of cell biologyWas this review helpful? Yes NoThank you for your feedback. Report this reviewThank you, this review has been flagged.
Posted February 25, 2001
I have to admit, my cell and molecular bio professor is less than perfect. He often skips over key concepts in his lectures and moves a little faster than my classmates and I would like. This book certainly makes up for the tremendous gap between what is required to be known in the class and what is taught by the teacher. The point of this message is that you should not feel at all bad about spending 65 dollars on this book if it is required for a class of yours, or even if it isn't. If you read it thoroughly, you will have no trouble understanding key concepts of cell and molecular biology required for many undergraduate level courses.
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