Cells are the basic units of life. All living things are made up of cells. Some animals and plants consist of only one cell. Other plants and animals are made up of many cells. The body of a man has more than a million of cells (100 trillion cells). A cell is composed primarily of four elements – carbon, hydrogen, oxygen, and nitrogen and trace elements. Living things are composed of over 60% water. The major building substances of cells are proteins.

1. Structural Basis of Life
By Prof. Liwayway Memije-Cruz

3. Cell Physiology
All cells exhibit irritability, digest foods,
excrete waste, and are able to reproduce,
grow, move and metabolize. Concentrating
on cell environments developed cell
physiology. Physiologists found out that
human cells survive only in highly
specialized environments composed of
minerals, water, nutrients and other
constituents.

4. Principles of cell theory:
In 1838 and 1839, Matthias Jacob Schleiden, a
German botanist and Theodor Schwann, a
German zoologist published the so-called cell
theory. They stated the principle with particular
clarity, and later gained the general acceptance
of the scientists during their time. According to
them:
 All organisms are composed of one or more cells.
 The cell is the basic living unit of organization.
 All cells arise from pre- existing cells.

5. INTRODUCTION
• Cells are the basic units of life.
• All living things are made up of cells.
Some animals and plants consist of
only one cell. Other plants and
animals are made up of many cells.
• The body of a man has more than a
million of cells (100 trillion cells).
• A cell is composed primarily of four
elements – carbon, hydrogen, oxygen,
and nitrogen and trace elements.
Living things are composed of over
60% water.
• The major building substances of
cells are proteins. They are organized
into groups and layers called tissues.
• Cells vary in size from microscopic to
over a meter in length. The cells of
different tissues vary in size, shape,
arrangement, and function.
Intercellular materials whose
composition varies from solid to liquid
separate cells.

6. Major parts of a typical cell:
Nucleus
 governs the activities of the cell
 necessary for reproduction. The nucleus
contains genetic material called
deoxyribonucleic acid (DNA), which carries
hereditary instructions
 directs the production of proteins.
 is the structure, usually found near the center
of the cell that contains the cell’s hereditary
material.

7. Characteristic structures of the nucleus
Nuclear envelope, which is a two –
membrane boundary between the
inside of the nucleus and that of the
cytoplasm.
Nucleoplasm, which is the fluid
portion of the nucleus.
Chromosomes, which are substances
containing DNA, the cell’s hereditary
materials and package DNA and
control gene expression.
Nucleolus, which is a dense cluster
of DNA and materials used to
assemble the sub units of ribosome.

8. Cytoplasm
• the part of the cell where
most cellular activities occur.
• its fluid substance called
cytosol contains inclusions,
stoned or inactive such as fat
globules, water vacuoles,
crystals in the cytoplasm and
specialized bodies known as
organelles.
• a site of metabolic reactions,
in which the cytoplasmic
organelles play specific roles.
The specialized organelles are:
 MITOCHONDRIA, WHICH ARE THE
CELL’S POWER PLANTS, WHICH
PRODUCE MOST OF THE ENERGY.
 GOLGI BODIES, WHICH TRANSPORT
PROTEINS AND OTHER MATERIALS.
 LYSOSOMES, WHICH ARE FOR
DEGRADATION AND RECYCLING OF
MATERIALS.
 ENDOPLASMIC RETICULUM, WHICH
IS A SYSTEM OF DEEP CHANNELS
THAT WINDS THROUGHOUT THE
CYTOPLASM. MANUFACTURES
PROTEINS, LIPID COMPONENTS OF
MEMBRANE AND MODIFIES
PROTEINS FOR SECRETION.
 PEROXISOMES, WHICH DISARM
DANGEROUS CHEMICAL IN THE
CELLS.
 RIBOSOMES, WHICH ARE TINY,
ROUND BODIES THAT BORDER THE
ENDOPLASMIC RETICULUM THAT
ARE RESPONSIBLE FOR PROTEIN
SYNTHESIS.

9. Plasma membrane
 The plasma membrane limits and encloses the
cytoplasm and acts as a selective barrier to
the movement of substances into and out of
the cell. It is composed of a bilipid layer
containing proteins. The water -
impermeable lipid portion forms the basic
fibers of the membranes. Proteins act as
enzymes or carriers in membrane transport,
form pores, provide reception sites for
hormones and other chemicals or play a role
in cellular replication and interactions during
development and immune reactions.
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