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CELL
THEORY
The ideas of the
cell theory:
1. All organisms
are made up cells.
2. All cells
carry on their life activities.
3. New cells are
formed by parent cell.
PROCARYOTIC
Prokaryotic
cells dont have nucleus and membraneous
organelles.
EXAMPLES OF
PROKARYOTIC CELL
Bacteria (Sing:
Bacterium)
MAIN
PARTS OF PROKARYOTIC CELLS
Cell membrane
Cytoplasm
Ribosome
Hereditary Materials(DNA)
Eucaryotic
Cells
Eucaryotic
cells have true nucleus and membranous organelles.
Human,
plants, animals and fungi have Eucaryotic cells.
MAIN
PARTS OF EUKARYOTIC CELLS
Cell Membrane
Cytoplasm
Nucleus
CELL
MEMBRANE
The
cell membrane or plasma membrane separates the cell from the environment. Cell
is covered by cell membrane.
Cell
membrane is thin layer. We can't see cell membrane under the light microscope
but we can see under the electron microscope.
Structure
of cell membrane
It is two layered structure composed of lipid, protein and carbohydrate.
Two
layers are lipids and proteins are embedded in them.
Carbohydrates are found outer surface of the cell membrane.
This model of cell membrane is called fluid mosaic model.
PORE
Cell
membrane has small pores in its structure. Materials pass through the pores into
or out of the cell.
The
cell membrane is selectively permeable or semipermeable. That is; some
substances pass freely through it. Other substances can pass through cell
membrane at the certain times or can not pass.
The
Transport of Materials Across the Cell membrane
1.Passive
transport
Energy is not used to move substances into or out of
the cell in passive transport.
There are two types of passive transport. These are
diffusion and osmosis.
DIFFUSION
Diffusion
is the movement of material from high concentration to a low concentration.
Diffusion occurs in both living and non-living things.
Monosaccharides,
amino acid, fatty acid, glycerol, vitamins, water and other small compounds can
pass through the cell membrane by diffusion.
OSMOSIS
Osmosis is the diffusion of water across a
semipermeable membrane.
PLASMOLYSIS
When
a cell is placed into a hypertonic
environment; cell gives water to environment from its cytoplasm and it shrinks.
A
hypertonic solution contains a higher concentration of dissolved substances then
the cells.
DEPLASMOLYSIS
If
a cell is put into a hypotonic environment; cell absorbs water from its
environment and it swells.
A hypotonic solution contains lower concentration of
dissolve substances then the cell. If the cell has no cell wall for expelling
the excess water it will burst.
OSMOTIC
PRESSURE
If
a cell has hypertonic cytoplasm; it wants to absorb water from its environment.
This absorption
force is called osmotic pressure.
Cells
of root have high osmotic pressure.
TURGOR
PRESSURE
During the deplosmolysis, the cell absorbs water and the volume of its
cytoplasm increases. As a result, the plasma membrane is stretched due to the
large volume of fluid exerting pressure on it. This pressure is known as turgor
pressure.
Factors
Affecting The Rate Of Passive
Transport
Molecular size
Molecular weight
Molecular charge
Temperature
Solubility in lipid
ACTIVE
TRANSPORT
Active transport is the movement of materials from low concentration to
high concentration by means of energy and carrier proteins.
In active transport small molecules can pass through the cell membrane;
like diffusion.
Taking of large liquid molecules into the cytoplasm is called pinocytosis.
Taking of large solid molecules into the cytoplasm is called phagocytosis.
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