lOMoARcPSD|24448587
ne
Bio 101
sh
BIO 101
ne
INTRODUCTORY BIOLOGY I la
tz
THE CELL
sh
Sp
A cell may be defined as he standard unit of biological activity bounded by a
ne
membrane, and able to reproduce itself independently of any other living system.
la
All living organisms, large and small, plant and animal, fish and fowl, man and
sh
Sp
microbe, are made up of cells. All cells are basically similar to each other, having
ne
many structural features in common. Organisms may be composed of only one
la
tz
cell, when we describe them as being unicellular, or of many cells when we say
sh
Sp
they are multicellular.
ne
With the exception of eggs, which are the largest cells (in volume) known, cells
la
are small and mostly invisible to the unaided eye. Consequently, our
sh
Sp
understanding of cells paralleled technical advances in the resolving power of
ne
microscopes. Englishman Robert Kooke first saw the remains of dead cells in
la
1665 in a piece of cork as he was using his newly invented microscope and he
tz
sh
coined the work <cell= to describe the tiny structures, thinking that they
Sp
ne
resembled the unadorned cells occupied by the monks. In 1838 Mathias
la
Schleiden, a German botanist, announced that all plant tissues were composed
sh
Sp
of cells. A year later one of his countrymen, Theodor Schwann, described animal
ne
cells as being similar to plant cells. Schleiden and Schwann are thus credited
la
with the unifying cell theory. Some 20 years after the announcements of
tz
sh
Sp
Schleiden and Schwann, Rudolf Virchow, a great German physician, made
ne
another important generalization, cells come only from pre-existing cells.
la
Cells are separated from their external environment by an interface or plasma
sh
membrane. Everything inside the plasma membrane is sometimes referred to as
Sp
ne
protoplasm, consisting of the jelly like cytoplasm (cyto-cell, plasma thing) and
a
various structures collectively known as organelleles, including the membrane,
tz
l
sh
bound nucleus. Each organelles represents a highly specialized compartment or
Sp
ne
submodule in which particular functions of the cell are localized.
la
(diagram)
sh
Sp
la
Downloaded by Martin muthii ()
Sp
, lOMoARcPSD|24448587
ne
Bio 101
sh
STRUCTURE AND FUNCTIONS
ne
The Plasma membrane: Typically the eukaryotic cell is enclosed within a thin,
la
tz
study, differentially permeable plasma membrane. This structure regulates the
sh
Sp
flow of materials between the cell and its surroundings. In some cells, such as
ne
nerve cells, the plasma membrane also is involved in intercellular communication
la
in other cells, such as intestinal epithelium, the plasma membrane is modified
sh
Sp
into numerous, small, finger like projection called microvilli that increase the
ne
surface area of the cell. Chemically, the membrane consists of lipid (fatty
la
tz
material)and protein.
sh
Sp
Endoplasmic reticulum and ribosomes: transport, storage and synthesis: The
ne
endoplasmic reticulum is visible in great detail with the electron microscope and
la
consist of an extensive network of membrane-enclosed spaces. The space is
sh
Sp
referred to as the Cisternea. The membranes of the endoplasmic reticulum may
ne
appear smooth along their outer surface. However, sometimes the outer surface
la
tz
is studied with small particles called ribosomes, and in this case the
sh
Sp
endosplasmic reticulum has a coarse appearance and is spoken of as rough. The
ne
R.E.R. is found with greater frequency and abundance in cells which are actively
la
synthesizing protein. The manufacture of proteins in the cell is associated with
sh
Sp
the ribosomes, which are dense particles containing protein and ribonucleic acid
ne
(RNA).
la
tz
The E.R. by virtue of its extensive branching, functions in transport, the cisternea
sh
Sp
of the |E. R. apparently function as roots for transport of certain substances
ne
within the cell. In some cases, the ER accumulates large masses of protein and
la
acts in a storage capacity.
sh
Sp
ne
The Golgi complexe: is a stack of smooth, membraneous cisternae that
a
tz
functions in the storage, modification and packaging of protein products,
l
sh
Sp
especially secretory products. It does not synthesize protein but may add
ne
polysaccharide to the complex. As its products mature, the ends of the cisternea
la
pinch off and become membrane-bound vesicles in the cytoplasm. The contents
sh
Sp
la
Downloaded by Martin muthii ()
Sp
, lOMoARcPSD|24448587
ne
Bio 101
sh
of some of these secretory products destined to be exported from a glandular
ne
cell. Pothers may contain digestive enzymes that remain in the cell that produce
la
tz
them. Such vesicles are called Lysosomes (literally <loosening body=, a body
sh
Sp
capable of causing lysis, or disintegration). The enzymes they contain are
ne
involved in the breakdown of foreign materials, including bacteria engulfed by
la
the cells. Lysosomes are also capable of breaking down injured or diseased cells
sh
Sp
and worn-out cellular components, since the enzymes they contain are so
ne
powerful that they kill the cell that formed them if the lysosomes membrane
la
tz
ruptures. In normal cells the enzymes remain safely enclosed within the
sh
Sp
protective membrane.
ne
la
Mitochondria: There organelles are conspicuous organelles present in nearly all
sh
Sp
eukaryotic cells. They are diverse in size, number and shape, some are rodlike,
ne
and others are more or less spherical. They may be scattered uniformly the
la
tz
cytoplasm, or they may be localized near cell surfaces and other regions where
sh
Sp
there is unusual metabolic activity. The mitochondrion is composed of a double
ne
membrane. The outer membrane is smooth, whereas the inner membrane is
la
folded into numerous platelike projections called cristae. These characteristics
sh
Sp
features make mitochondria easy to identify among the organelles. They are
ne
often called <powerhouse of the cell= because enzymes located on the cristae
la
tz
carry out the energy-yielding steps of aerobic metabolism. ATP, the most sh
Sp
important energy storage molecule of the cells, is produced in the organelle.
ne
Mitochondria are self-replicating.
la
sh
Sp
Chloroplasts: The food we eat and the oxygen we breath are produced by
ne
organelles called chloroplasts. They are found in green plants. They are disc-
a
tz
shaped bodies containing a green pigment called chlorophyll. The complex
l
sh
Sp
chemical processes of photosynthesis take place in the chloroplast where the
ne
energy of sunlight is trapped and utilized for the synthesis of complex organic
la
materials from simple inorganic molecules.
sh
Sp
la
Downloaded by Martin muthii ()
Sp
, lOMoARcPSD|24448587
ne
Bio 101
sh
Each chloroplast is surrounded by two membranes that enclosed its contents and
ne
separate it from the cytoplasm. The internal portion of the chloroplast consists
la
tz
mainly of two parts: a fluid matrix (stroma) surrounding a complex membrane.
sh
Sp
The membrane system generally consists of a series of multilayered fluid-fluid
ne
discs (grana) resembling a stack of coins and a system of closed flat sacs
la
(lamellae) extending throughout the chloroplast and connecting the grana.
sh
Sp
Higher plants contain a variety of intracellular bodies called plastids. Usually
ne
there are two types; the chromoplasts (coloured bodies) and leucoplasts (white
la
tz
or colourless bodies). Chloroplasts belong to the chromoplasts group. Other
sh
Sp
kinds of chromoplasts give many flowers and leaves their colours or yellow,
ne
orange or red. Leucoplasts serve as food storage deposits for the cell and
la
contain oil, starch grains and protein.
sh
Sp
ne
Vacuoles: inner space: The cell may contain fluid filled spaces surrounded by a
la
tz
membrane, called vacuoles. Plant cells have more prominent vacuoles in young
sh
Sp
plant cells the vacuoles are many and they are rather small, but as the plant
ne
ages (gets older), these vacuoles fuse to form a large, conspicuous central
la
vacuole. The hydrostatic (fluid) pressure of the vacuole forces the cytoplasm to
sh
Sp
the periphery of the cell, and there it remains as a thin layer closely pressed
ne
against the plasma membrane. The vacuole of plant cells contains primarily
la
tz
water and a watery of other substances together called cell sap, because cell sap
sh
Sp
has a higher osmotic pressure than the external medium, water moves into the
ne
cell and the cell becomes turgid. It does not burst because it is surrounded by a
la
rigid cell wall. The turgid nature of the plant cell contribute to the strength of
sh
Sp
certain plant stems and the crispness of vegetables such as celery and lettuce.
ne
The plant cell stores a number of important substances in the variety fluids of
a
tz
the vacuole, and these include amino acids, proteins, salts, sugars and the red
l
sh
Sp
pigment anthocyanin. The red colour of roses, and red onions is due to the
ne
presence of anthocynanims in their vacuolar fluid. Vacuoles are formed in
la
animal cells during the processes of pinocytosis and phagocytosis.
sh
Sp
la
Downloaded by Martin muthii ()
Sp
ne
Bio 101
sh
BIO 101
ne
INTRODUCTORY BIOLOGY I la
tz
THE CELL
sh
Sp
A cell may be defined as he standard unit of biological activity bounded by a
ne
membrane, and able to reproduce itself independently of any other living system.
la
All living organisms, large and small, plant and animal, fish and fowl, man and
sh
Sp
microbe, are made up of cells. All cells are basically similar to each other, having
ne
many structural features in common. Organisms may be composed of only one
la
tz
cell, when we describe them as being unicellular, or of many cells when we say
sh
Sp
they are multicellular.
ne
With the exception of eggs, which are the largest cells (in volume) known, cells
la
are small and mostly invisible to the unaided eye. Consequently, our
sh
Sp
understanding of cells paralleled technical advances in the resolving power of
ne
microscopes. Englishman Robert Kooke first saw the remains of dead cells in
la
1665 in a piece of cork as he was using his newly invented microscope and he
tz
sh
coined the work <cell= to describe the tiny structures, thinking that they
Sp
ne
resembled the unadorned cells occupied by the monks. In 1838 Mathias
la
Schleiden, a German botanist, announced that all plant tissues were composed
sh
Sp
of cells. A year later one of his countrymen, Theodor Schwann, described animal
ne
cells as being similar to plant cells. Schleiden and Schwann are thus credited
la
with the unifying cell theory. Some 20 years after the announcements of
tz
sh
Sp
Schleiden and Schwann, Rudolf Virchow, a great German physician, made
ne
another important generalization, cells come only from pre-existing cells.
la
Cells are separated from their external environment by an interface or plasma
sh
membrane. Everything inside the plasma membrane is sometimes referred to as
Sp
ne
protoplasm, consisting of the jelly like cytoplasm (cyto-cell, plasma thing) and
a
various structures collectively known as organelleles, including the membrane,
tz
l
sh
bound nucleus. Each organelles represents a highly specialized compartment or
Sp
ne
submodule in which particular functions of the cell are localized.
la
(diagram)
sh
Sp
la
Downloaded by Martin muthii ()
Sp
, lOMoARcPSD|24448587
ne
Bio 101
sh
STRUCTURE AND FUNCTIONS
ne
The Plasma membrane: Typically the eukaryotic cell is enclosed within a thin,
la
tz
study, differentially permeable plasma membrane. This structure regulates the
sh
Sp
flow of materials between the cell and its surroundings. In some cells, such as
ne
nerve cells, the plasma membrane also is involved in intercellular communication
la
in other cells, such as intestinal epithelium, the plasma membrane is modified
sh
Sp
into numerous, small, finger like projection called microvilli that increase the
ne
surface area of the cell. Chemically, the membrane consists of lipid (fatty
la
tz
material)and protein.
sh
Sp
Endoplasmic reticulum and ribosomes: transport, storage and synthesis: The
ne
endoplasmic reticulum is visible in great detail with the electron microscope and
la
consist of an extensive network of membrane-enclosed spaces. The space is
sh
Sp
referred to as the Cisternea. The membranes of the endoplasmic reticulum may
ne
appear smooth along their outer surface. However, sometimes the outer surface
la
tz
is studied with small particles called ribosomes, and in this case the
sh
Sp
endosplasmic reticulum has a coarse appearance and is spoken of as rough. The
ne
R.E.R. is found with greater frequency and abundance in cells which are actively
la
synthesizing protein. The manufacture of proteins in the cell is associated with
sh
Sp
the ribosomes, which are dense particles containing protein and ribonucleic acid
ne
(RNA).
la
tz
The E.R. by virtue of its extensive branching, functions in transport, the cisternea
sh
Sp
of the |E. R. apparently function as roots for transport of certain substances
ne
within the cell. In some cases, the ER accumulates large masses of protein and
la
acts in a storage capacity.
sh
Sp
ne
The Golgi complexe: is a stack of smooth, membraneous cisternae that
a
tz
functions in the storage, modification and packaging of protein products,
l
sh
Sp
especially secretory products. It does not synthesize protein but may add
ne
polysaccharide to the complex. As its products mature, the ends of the cisternea
la
pinch off and become membrane-bound vesicles in the cytoplasm. The contents
sh
Sp
la
Downloaded by Martin muthii ()
Sp
, lOMoARcPSD|24448587
ne
Bio 101
sh
of some of these secretory products destined to be exported from a glandular
ne
cell. Pothers may contain digestive enzymes that remain in the cell that produce
la
tz
them. Such vesicles are called Lysosomes (literally <loosening body=, a body
sh
Sp
capable of causing lysis, or disintegration). The enzymes they contain are
ne
involved in the breakdown of foreign materials, including bacteria engulfed by
la
the cells. Lysosomes are also capable of breaking down injured or diseased cells
sh
Sp
and worn-out cellular components, since the enzymes they contain are so
ne
powerful that they kill the cell that formed them if the lysosomes membrane
la
tz
ruptures. In normal cells the enzymes remain safely enclosed within the
sh
Sp
protective membrane.
ne
la
Mitochondria: There organelles are conspicuous organelles present in nearly all
sh
Sp
eukaryotic cells. They are diverse in size, number and shape, some are rodlike,
ne
and others are more or less spherical. They may be scattered uniformly the
la
tz
cytoplasm, or they may be localized near cell surfaces and other regions where
sh
Sp
there is unusual metabolic activity. The mitochondrion is composed of a double
ne
membrane. The outer membrane is smooth, whereas the inner membrane is
la
folded into numerous platelike projections called cristae. These characteristics
sh
Sp
features make mitochondria easy to identify among the organelles. They are
ne
often called <powerhouse of the cell= because enzymes located on the cristae
la
tz
carry out the energy-yielding steps of aerobic metabolism. ATP, the most sh
Sp
important energy storage molecule of the cells, is produced in the organelle.
ne
Mitochondria are self-replicating.
la
sh
Sp
Chloroplasts: The food we eat and the oxygen we breath are produced by
ne
organelles called chloroplasts. They are found in green plants. They are disc-
a
tz
shaped bodies containing a green pigment called chlorophyll. The complex
l
sh
Sp
chemical processes of photosynthesis take place in the chloroplast where the
ne
energy of sunlight is trapped and utilized for the synthesis of complex organic
la
materials from simple inorganic molecules.
sh
Sp
la
Downloaded by Martin muthii ()
Sp
, lOMoARcPSD|24448587
ne
Bio 101
sh
Each chloroplast is surrounded by two membranes that enclosed its contents and
ne
separate it from the cytoplasm. The internal portion of the chloroplast consists
la
tz
mainly of two parts: a fluid matrix (stroma) surrounding a complex membrane.
sh
Sp
The membrane system generally consists of a series of multilayered fluid-fluid
ne
discs (grana) resembling a stack of coins and a system of closed flat sacs
la
(lamellae) extending throughout the chloroplast and connecting the grana.
sh
Sp
Higher plants contain a variety of intracellular bodies called plastids. Usually
ne
there are two types; the chromoplasts (coloured bodies) and leucoplasts (white
la
tz
or colourless bodies). Chloroplasts belong to the chromoplasts group. Other
sh
Sp
kinds of chromoplasts give many flowers and leaves their colours or yellow,
ne
orange or red. Leucoplasts serve as food storage deposits for the cell and
la
contain oil, starch grains and protein.
sh
Sp
ne
Vacuoles: inner space: The cell may contain fluid filled spaces surrounded by a
la
tz
membrane, called vacuoles. Plant cells have more prominent vacuoles in young
sh
Sp
plant cells the vacuoles are many and they are rather small, but as the plant
ne
ages (gets older), these vacuoles fuse to form a large, conspicuous central
la
vacuole. The hydrostatic (fluid) pressure of the vacuole forces the cytoplasm to
sh
Sp
the periphery of the cell, and there it remains as a thin layer closely pressed
ne
against the plasma membrane. The vacuole of plant cells contains primarily
la
tz
water and a watery of other substances together called cell sap, because cell sap
sh
Sp
has a higher osmotic pressure than the external medium, water moves into the
ne
cell and the cell becomes turgid. It does not burst because it is surrounded by a
la
rigid cell wall. The turgid nature of the plant cell contribute to the strength of
sh
Sp
certain plant stems and the crispness of vegetables such as celery and lettuce.
ne
The plant cell stores a number of important substances in the variety fluids of
a
tz
the vacuole, and these include amino acids, proteins, salts, sugars and the red
l
sh
Sp
pigment anthocyanin. The red colour of roses, and red onions is due to the
ne
presence of anthocynanims in their vacuolar fluid. Vacuoles are formed in
la
animal cells during the processes of pinocytosis and phagocytosis.
sh
Sp
la
Downloaded by Martin muthii ()
Sp
