SOLUTIONS TO EXERCISES, LESSON 2
All substances that enter or leave a cell must in some way pass through the cell
membrane. Resembling a circulatory system for the individual cell is the endoplasmic
reticulum. Granular particles concerned with protein synthesis are the ribosomes.
Spaces or cavities that serve functions at the cellular level such as digestion,
respiration, excretion, and storage are the vacuoles. A portion of the endoplasmic
reticulum that aids in the final preparation of certain proteins and mucus-like substances
is the Golgi complex. The "powerhouses" of the cell are the mitochondria. Playing a
major role in cell division are the two centrioles.
Each chromosome has a set of specific genes. These determine the physical
and chemical characteristics of the body. (para 2-2)
Adenosine triphosphate (ATP) provides energy for cellular processes such as
active transport of substances across membranes, synthesis of chemical compounds
for the body, mechanical work (such as muscle contraction). When an ATP molecule
provides energy for such a process, it loses a phosphate radical and becomes ADP.
Then, the cycle begins again as ADP is converted into ATP within the mitochondria.
The major component of living substances is water. The fluid within the cell is
called intracellular fluid. Located among the cells is the interstitial fluid. In the
circulatory systems, fluids serve as a vehicle. Together, the interstitial and circulating
Certain chemicals dissociate into ions when they are dissolved. These
chemicals are called electrolytes. For good health, these chemicals must be in balance.
In other words, each fluid compartment must have a certain concentration of a given
Water has several important physical characteristics: First, it is a fluid; therefore,
it has the capacity of flow. Second, it is able to dissolve many substances within itself;
thus, it is an excellent vehicle. Because of its heat-carrying capacity and its ability to
remove large numbers of calories during evaporation, water is very useful in controlling
The human body obtains water in two primary ways: First, water is the major
component of items we drink or eat. Second, as food substances are oxidized within
individual cells, water is one of the main by-products. (para 2-7b)
Water is lost from the body during perspiration, respiration, urination, vomiting,
Substances dissolved in the water of the body include gases, nutrients, wastes,