Fundamentals of Anatomy and Physiology

52 Chapter 3

Career

Focus

These are careers that are available to individuals interested in cellular structure and

function:

●● Cell biologists study the anatomy and function of cellular organelles and have careers-

working in universities and medical centers as researchers and technicians.^

●● Electron microscopists, equipped with special training in operating an electron

microscope,- find employment in hospitals, research universities, industry, and

pharmaceutical companies.

Summary Outline
membrane. It is through the membrane that materi-als
enter and exit the cell.

Introduction (^) Cytoplasm Of The Cell

1. The cell is the basic unit of biologic organization. It
   is composed of a fluid medium called protoplasm
   surrounded by a cell or plasma membrane. Struc-

tures within this protoplasm are called organelles.^

2. The protoplasm inside the nucleus is called nucleo-
   plasm; the protoplasm outside the nucleus is called
   cytoplasm.

The History of the Discovery of DNA.

1. Two Germans, Matthias Schleiden, a botanist, and
   Theodor Schwann, a zoologist, were the first biolo-

gists to propose the cell theory in the 1830s.^

2. The modern cell theory states that cells are the basic
   units of organization of all organisms; all organisms
   are composed of one or more cells; cells arise from
   only preexisting cells through cell division; and all ex-
   isting cells are the descendants of the first cells formed
   early in the evolutionary history of life on earth.

The Cell Membrane

1. The cell membrane or plasma membrane is made up of
   a double phospholipid layer with proteins em-bedded

in the phospholipid layer.^

2. The phospholipid layer allows for the free passage of
   water molecules through the cell membrane via osmo-
   sis, while the proteins act as channels, active transport

areas, receptor sites, and identity markers for the cell.^

3. This molecular arrangement of the cell mem-brane
   is referred to as a fluid mosaic model and is
   responsible for the selective permeability of the
   
   
   1. The main constituent of cytoplasm is water. Chemi-
      cal compounds like the mineral salts are dissolved in
      solution in this water; chemical compounds with the
      C-H bond (organic molecules) are in colloidal
      suspension.^
   
   
   
   


4. In a solution, individual atoms or ions are distrib-
   uted throughout the watery medium; in a colloid,
   clumps of atoms rather than individual atoms are
   distributed throughout the watery medium.^


5. The water molecule has unique properties, which
   determine whether molecules will go into^
   solution- or a colloidal suspension. The oxygen atom
   in H 2 O has a stronger attraction for the electrons in
   the H{O bond than the hydrogen atoms; thus, the
   oxygen atom is slightly nega-tive, whereas the two
   hydrogen atoms are slightly positive.


6. Polar compounds, such as the ionically bonded
   mineral salts, will dissolve in water and go^
   into solution;- nonpolar compounds, such as
   the covalently- bonded molecules of proteins,^
   carbohydrates,- fats, and nucleic acids, will go into
   colloidal suspension.^


7. The cytoplasm of the cell will also contain storage
   granules, fat droplets, and vacuoles.

The Nucleus.

1. The nucleus is the control center of the cell. It is
   surrounded by a double nuclear membrane. The inner
   nuclear membrane surrounds the fluid part of