THE CELL PHYSIOLOGY
CELL STRUCTURE
The cell is the smallest structural and functional unit of the body.
The human body contains about 100 trillion cells.
Different types of cells of the body possess features which distinguish one type from
the other, and are specially adapted to perform particular functions,
e.g. the red blood cells transport oxygen from lungs to the tissues, muscle cell is
specialized for the function of contraction.
A typical cell, as seen by the light microscope, consists of three basic components:
Cell membrane,
Cytoplasm
Nucleus.
FIG:Structure of a typical cell (in the centre) showing various organelles: A, mitochondrion; B, endoplasmic reticulum
(rough and smooth); C, Golgi apparatus; D, centrosome; E, nucleus and F, secretory granules
CELL MEMBRANE
Cell membrane or the plasma membrane is the protective sheath enveloping the cell
body.
It separates the contents of cell from the external environment and controls
exchange of materials between the fluid outside the cell (extracellular fluid) and the
fluid inside the cell (intracellular fluid)
Singer and Nicholson put forward the fluid mosaic model of membrane structure
Phospholipid bilayer is the basic continuous structure forming the cell membrane.
The phospholipids are present in fluid form.
, This fluidity makes the membrane quite flexible and thus allows the cells to undergo
considerable changes in the shape without disruption of structural integrity.
The protein molecules are present as a discontinuous mosaic of globular proteins
which float about in the fluid phospholipid bilayer forming a fluid mosaic pattern
CYTOPLASM
Cytoplasm is an aqueous substance (cytosol) containing a variety of cell organelles and
other structures. The structures dispersed in the cytoplasm can be broadly divided into
three groups: organelles, inclusion bodies and cytoskeleton.
A. ORGANELLES
The organelles are the permanent components of the cells which are bounded by
limiting membrane and contain enzymes; hence participate in the cellular metabolic
activity. These include the following.
1. Mitochondria
Mitochondria are the major sites for aerobic respiration. These are oval structures
and more numerous in metabolically active cells.
Structure:The mitochondria consist of:
o Membrane.
There are two layers of the membrane. The outer smooth and inner folded
into incomplete septa called cristae
CELL STRUCTURE
The cell is the smallest structural and functional unit of the body.
The human body contains about 100 trillion cells.
Different types of cells of the body possess features which distinguish one type from
the other, and are specially adapted to perform particular functions,
e.g. the red blood cells transport oxygen from lungs to the tissues, muscle cell is
specialized for the function of contraction.
A typical cell, as seen by the light microscope, consists of three basic components:
Cell membrane,
Cytoplasm
Nucleus.
FIG:Structure of a typical cell (in the centre) showing various organelles: A, mitochondrion; B, endoplasmic reticulum
(rough and smooth); C, Golgi apparatus; D, centrosome; E, nucleus and F, secretory granules
CELL MEMBRANE
Cell membrane or the plasma membrane is the protective sheath enveloping the cell
body.
It separates the contents of cell from the external environment and controls
exchange of materials between the fluid outside the cell (extracellular fluid) and the
fluid inside the cell (intracellular fluid)
Singer and Nicholson put forward the fluid mosaic model of membrane structure
Phospholipid bilayer is the basic continuous structure forming the cell membrane.
The phospholipids are present in fluid form.
, This fluidity makes the membrane quite flexible and thus allows the cells to undergo
considerable changes in the shape without disruption of structural integrity.
The protein molecules are present as a discontinuous mosaic of globular proteins
which float about in the fluid phospholipid bilayer forming a fluid mosaic pattern
CYTOPLASM
Cytoplasm is an aqueous substance (cytosol) containing a variety of cell organelles and
other structures. The structures dispersed in the cytoplasm can be broadly divided into
three groups: organelles, inclusion bodies and cytoskeleton.
A. ORGANELLES
The organelles are the permanent components of the cells which are bounded by
limiting membrane and contain enzymes; hence participate in the cellular metabolic
activity. These include the following.
1. Mitochondria
Mitochondria are the major sites for aerobic respiration. These are oval structures
and more numerous in metabolically active cells.
Structure:The mitochondria consist of:
o Membrane.
There are two layers of the membrane. The outer smooth and inner folded
into incomplete septa called cristae
