2. CELL DEFINITION:
“A human cell can be defined as mass of
protoplasm enveloped by a cell
membrane, containing at least one
nucleus”
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3. Introduction
A cell is the basic, living, structural, and functional unit of the body.
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Cytology is the study of cell structure
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Cell physiology is the study of cell function.
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The cell can be divided into following principal parts for ease of
study.
Plasma (cell) membrane
1.
Cytoplasm
2.
Cell organelles (except nucleus)
3.
Nucleus
4.
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4. PROTOPLASM:
Protoplasm is the whole content of a cell enclosed within the cell
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membrane, including both the cytoplasm and nucleus.
Cytoplasm is the content of the cell except the nucleus .
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Protoplasm is the " living substance" of the cell.
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It can be differentiated into cytoplasm and the nucleus.
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Inside the nucleus protoplasm is called karyoplasm or neucleoplasm.
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Remainder of the protoplasm is called cytoplasm.
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5. Physical properties of protoplasm
the consistency varying from the more liquid, slightly
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gelatinous white of a fresh egg to that of semi-solidified
gelatin of jelly.
If the protoplasm is more liquid it is termed a sol, if
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more gelatinous, a gel.
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6. Chemical and physical properties of
protoplasm
It is a transparent and jelly-like material.
Chemical protoplasm can be divided into inorganic and organic
substances
Inorganic substances:
Inorganic substances are water, which make up 90% of the
protoplasm, mineral salts, such as NaCl-salt, and gases like oxygen
and carbon dioxide.
Organic substances:
Organic substances include proteins, carbohydrates, lipids, nucleic
acids and enzymes.
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7. Function of protoplasm
Reproduction- Cells divide to form identical daughter cells; function of
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the nucleus of the protoplasm
Responsiveness- The living protoplasm responds to stimuli, e.g. retinal
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cells in the eye respond to light.
Chemical- All the functions are carried out inside the cell, e.g. respiration
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in the mitochondria;
Excretion- Cells must get rid of excretory wastes; they usually diffuse out
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of the cell through the cell membrane
Movement-Movement is exhibited by certain cells, e.g. unicells; the
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protoplasm of these cells has a contractile ability.
Growth- cells can divide and grow
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8. Physical structure of the cell
Cell membrane
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Cytoplasm
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Cell organelles
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Nucleolus
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11. Cell membrane
The plasma(cell) membrane is a structure that
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borders the entire cell separating the internal
environment from the external environment.
Exhibits a 3-layered structure also called unit
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membrane.
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12. Cell membrane is composed of
Lipids (phospholipids ,cholesterol)
1.
Proteins
2.
Carbohydrates (oligosaccharides)
3.
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Cell membrane chemical composition
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13. Select this paragraph to edit
THE FLUID-MOSAIC MEMBRANE MODEL:
According to the most accepted model called fluid mosaic model
C.M consists of:
Bimolecular or double layer of mixed phospholipids (lecithin and
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cephalin).
Protein and cholesterol are intercalated in lipid bilayer
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The phospholipids are made of two long, non-polar, hydrophobic
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hydrocarbon chains which are attached to a charged head
(hydrophilic) group.
In the lipid bilayer the hydrophilic heads lie at the outer and inner
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faces of cell membrane while the hydrophobic chains project
towards the middle of the bilayer.
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Cell membrane chemichecal
composition
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Cell membrane chemichecal composition
14. The Fluid-Mosaic Membrane Model
According to fluid musaic model cell membranes are not
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static; they have a fluid consistency.
Most membrane lipids and proteins can drift about laterally in
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the plane of the membrane.
Cholesterol enhances membrane fluidity, allows animal
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membranes to function in a wide range of temperatures and
also makes the membrane less permeable to biological
molecules.
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17. Select this paragraph to edit
C.M proteins also called integral proteins are distributed as globular
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molecules intercalated among the phospholipids molecule.
Some of the proteins are partially embedded in lipid bilayer and
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they protrude from either inner or outer surface of the C.M.
But majority are long enough to protrude from both layers (inner and
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outer) surfaces of the C.M and are called trans membrane proteins.
These trans membrane proteins are transport channels for water
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soluble substance.
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Cell membrane proteins
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18. Cell Membrane Proteins:
Two Types:
Integral: Proteins that insert into the membrane (
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transmembrane proteins)
Peripheral: Proteins attached to the surface of the cell
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membrane.
Function:
Transportation
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Enzymes
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Receptor sites
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Cell adhesion
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Attachment to the cytoskeleton
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20. Glycocalyx (cell coat)
Some membrane proteins and lipids have carbohydrate
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chains which projects from the outer surface of the cell
membrane and form a coating over the external surface
this coating is called glycocalyx or cell coat.
It consists of highly branched oligosaccharides and
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polysaccharides
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21. Functions of glycocalyx
Due to negative charge repels other negative
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charge particles
Cell-cell recognition.
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Act as receptor substance for hormones
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such as: insulin
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22. 1: It serve as cell boundary and act as a barrier between cytoplasm and
external environment.
2: Cell membrane act as a transport channel for different substance.
Endocytosis: Ingestion or taking substances inside the cell is called
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endocytosis.
Exocytosis: release or excretion of substances by cell.
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Pinocytosis: ingestion of fluid substances by cell.
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Phagocytosis: ingestion of particulate matter(solid substances) by cell.
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3: cell membrane maintains cell shape and help in mobility.
4: In some cells it act as a medium for electrical impulse conduction.
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Cell membrane functions
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