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CELL AND CELL MEMBRANE
THEORY AND TRANSPORT MECHANISM
PREPARED BY: ALI ASHOUR
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CELL AND CELL MEMBRANE
Cells in our world come in two basic types,
prokaryotic and eukaryotic. "Karyose" comes from
a Greek word which means "kernel," as in a kernel
of grain. In biology, we use this word root to refer to
the nucleus of a cell. "Pro" means "before," and
"eu" means "true," or "good.“
So "Prokaryotic" means "before a nucleus," and
"eukaryotic" means "possessing a true nucleus."
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CELL AND CELL MEMBRANE
Here's a simple visual comparison between a prokaryotic cell and
a eukaryotic cell:
prokaryotic
eukaryotic
1-10 µ
Present without lipid
10-100 µ
Present with lipid
Cell wall
Present
Present in some cell
and absent in other
Nucleus
Not surround by nuclear envelope
surround by nuclear envelope
Circular DNA (plasmid)
absent
Linear Chromosomes
Present
Absorption
photosynthesis
Ingestion (phagocytosis)
Absorption
photosynthesis
Binary& multiple fission
budding
Binary fission , budding
mitosis and meiosis
Bacteria
cyan bacteria
Plant, animals, fungi and protozoa
Size
Plasma membrane
Chromosomes
Cytoplasm organelles
Nutrition
Cell division
Examples
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CELL AND CELL MEMBRANE
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CELL AND CELL MEMBRANE
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CELL AND CELL MEMBRANE
CELL MEMBRANE The thin barrier that separates the internal
components of the cell from the extracellular materials and
external environment. Also is the gatekeeper that regulates
passage of substances into and out of the cell.
Fluid mosaic model
A mosaic is a pattern of many small pieces fitted together.
According to this model, the membrane is a mosaic of proteins
floating like ice of bergs in a sea of lipids.
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CELL AND CELL MEMBRANE
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CELL AND CELL MEMBRANE
Membrane lipids
about 75% of the lipids are phospholipids. The phospholipids
line up in two parallel rows, forming a phospholipids (lipid)
bilayer..
This arrangement occurs because the phospholipids are
amphipathic, amphipathic means that, they have both
polar and non polar regions. the polar part is the
phosphate containing “head” which is hydrophilic “mixes
with water”. The non-polars are the two fatty acid “tails”
which are hydrophobic “do not mix with water”. The
molecules orient in the bilayer so that the heads face
outward on either side. The tails face each other in the
membranes interior.
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CELL AND CELL MEMBRANE
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CELL AND CELL MEMBRANE
Glycolipids, about 5% of membrane lipids, are also
amphipathic. They appear only in the layer that face the
extracellular fluid. They are important for adhesion
among cells and tissues, may mediate cell-to-cell
recognition and communication, and contribute to
regulation of cellular growth and development.
Cholesterol, the remaining 20% of membrane lipids are
cholesterol molecules, which are located among the
phospholipids in both sides of the bilayer in cells.
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CELL AND CELL MEMBRANE
Membrane proteins
Membrane proteins are of two types; integral and
peripheral.
Integral proteins; extend across the phospholipids
bilayer among the fatty acid tails. Most of integral
proteins are glycoproteins.
Peripheral proteins; do not extend across the
phospholipids bilayer. They are loosely attached to
the inner and outer surfaces of the membrane and
are easily separated
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MEMBRANE TRANSPORT PROCESSES
The mechanisms that enable substances to move
a cross cell membranes are essential to the life
of the cell. Certain substances, for example,
must move into the cell to support needed
biochemical reactions, while waste materials or
harmful substances must be moved out.
Mechanisms that move substances across a
membrane without using energy are passive
processes.
In active processes, the cell uses energy from
the splitting of ATP to move the substance
across the membrane.
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MEMBRANE TRANSPORT PROCESSES
Passive processes
Passive process, is the process by which substances
move down a concentration gradient from an area of
higher to lower concentration or pressure, cell dose
not expend energy. The passive processes that will
be discuss are
diffusion
osmosis
and filtration
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MEMBRANE TRANSPORT PROCESSES
Simple diffusion is the movement of molecules or
ions due to their kinetic energy. And occurs as
follows;
occurs as follows;
If a particular ion or molecules is present in high
concentration, in an area and in low concentration
in another area. When two such areas are
connected, more particles diffuse from the region
of high concentration to the region low
concentration. I.e. down or with their concentration
gradient, then diffuse in the opposite direction.
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MEMBRANE TRANSPORT PROCESSES
Simple diffusion is the movement of molecules or
ions due to their kinetic energy. And occurs as
follows;
Substances may also diffuse through a membrane
such as oxygen, carbon dioxide, nitrogen, steroids,
and fat-soluble vitamins “A, E, D & K”, urea,
glycerol, small alcohols, and ammonia diffuse
through the phospholipids bilayer of the plasma
membrane, into and out of cells.
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MEMBRANE TRANSPORT PROCESSES
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MEMBRANE TRANSPORT PROCESSES
Important examples include sodium ions
“Na+ ”, potassium ions “K+ ”, calcium ions
“Ca2+ ”, chloride ions “Cl- ”, and
bicarbonate ions “Hco3”.water itself also
diffuse into and out of cells through
protein-linked channels
diffusion of substances through channels
generally is much slower than diffusion
through the phospholipid bilayer.
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MEMBRANE TRANSPORT PROCESSES
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MEMBRANE TRANSPORT PROCESSES
Osmosis is the movement of solvent molecules, which is water
in living systems, across a selectively permeable membrane
from an area of higher to lower concentration of water until an
equilibrium is reached.
As an example of osmosis; a sac made of
cellophane, a permeable membrane that
permits water but not sugar molecules to pass,
is filled with a 20% sugar (sucrose) solution.
The sac is then placed into a beaker containing
distilled water.
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MEMBRANE TRANSPORT PROCESSES
Osmosis is the movement of solvent molecules, which is water
in living systems, across a selectively permeable membrane
from an area of higher to lower concentration of water until an
equilibrium is reached.
The water concentration on the two sides of the
cellophane membrane is different. There is a lower
water concentration inside the sac because the
addition of sugar molecules has decreased the water
concentration. As a result, osmosis occurs, water
moves a cross the membrane down its concentration
gradient from the beaker into the cellophane.
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MEMBRANE TRANSPORT PROCESSES
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MEMBRANE TRANSPORT PROCESSES
Filtration another passive process for moving
materials in and out of cell. Filtration, is
the process by which movement of
solvents “such as water” and solutes “such
as glucose” across a selectively permeable
membrane as a result of gravity or
hydrostatic “water” pressure from an area
of higher to lower pressure.
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MEMBRANE TRANSPORT PROCESSES
Active processes
Some substances that need to enter or leave body
cells cannot move a cross cell membrane
passively. Either they are too big, have the wrong
charge, or must move against the concentration
gradient. Such substances can cross the
membrane by active processes. Active process, is
the process by which cell expends energy by
splitting ATP to move substance, some times
against concentration gradient
Two principle types are active transport and bulk
transport;
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MEMBRANE TRANSPORT PROCESSES
Active transport is the movement of a substance across a cell membrane
from lower to higher concentration using energy derived from ATP either
directly or indirectly.
There are two types of active transport;
Primary active transport is the movement of ions
or molecules a cross a selectively permeable
membrane, often from a region of lower to
higher concentration by pump proteins that
split ATP. Energy derived from ATP directly.
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MEMBRANE TRANSPORT PROCESSES
Active transport is the movement of a substance across a cell membrane from
lower to higher concentration using energy derived from ATP either directly or
indirectly.
There are two types of active transport;
Secondary active transport symport sand antiports.
Is a simultaneous movement of two substances
across the membrane, one of which is Na+ . uses
energy supplied by the Na+ concentration gradient,
which maintained by primary active transport
pumps
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MEMBRANE TRANSPORT PROCESSES
Symport; process by which two substances, usually Na+ and
another substance, move in the same direction a cross the
plasma membrane. Also called contrasport.
Antiport; process by which two substances, usually Na+ and
another substance, move in opposite direction.
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MEMBRANE TRANSPORT PROCESSES
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MEMBRANE TRANSPORT PROCESSES
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MEMBRANE TRANSPORT PROCESSES
Bulk transport There are many types of bulk transport;
Phagocytosis “cell eating”
Movement of solid particles through the plasma
membrane , pseudopods extend around the
substance, enclose it, and bring it into the cell,
forming a phagocytic vesicle.
Pinocytosis “cell drinking”
Movement of extracellular fluid droplets into cell 
by in folding of plasma membrane forming
pinocytic vesicle, that allows the liquid to flow
inward and then surrounds the liquid.
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MEMBRANE TRANSPORT PROCESSES
Receptor-mediated endocytosis;
Mechanism for selected substances (ligands) to
move into cells, involves binding of ligand to
receptor of extracellular surface of plasma
membrane, membrane then folds inward, forming
endocytic vesicle.
 Exocytosis;
Export of substances from the cell in which vesicles
fuse with the plasma membrane and release their
contents into the extracellular fluid.
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MEMBRANE TRANSPORT PROCESSES
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MEMBRANE TRANSPORT PROCESSES
Experiment
Osmosis and cell membrane integrity
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MEMBRANE TRANSPORT PROCESSES
As we mentioned before, osmosis is the movement
of solvent molecules, which is water in living
systems, across a selectively permeable membrane
from an area of higher to lower concentration of
water, that means down its concentration gradient.
Purpose; To determine the effect of the external solution on RBC’s.
Material;
•Different concentration of saline solution: 0.3% NaCl, 0.9% NaCl, 3.0% NaCl
•Distilled water
•Fresh blood
•Test tube
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MEMBRANE TRANSPORT PROCESSES
Procedure;
1- Prepare 4 labeled test tube.
2-Add 4 ml of saline solution to each tube as follow;
•First tube: 4ml of 0.3% NaCl solution.
•Second tube: 4ml of 0.9% NaCl solution
•Third tube: 4ml of 3.0% NaCl solution
•Forth tube: 4ml of distilled water
3- Add 2 drops of fresh blood to each of the fore tube.
4- Shake well, then leaves the tube to stand from 10-30 minutes.
5- Take one drop from each tube and put it on a cleaned & labeled slide then
cover it with cover slip.
6- Examine under the microscope using X10 & X40 objective lenses.
7- Record your result then explain it i.e. what happen to the RBC when added
to hypertonic solution, hypotonic solution, and isotonic solution.
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MEMBRANE TRANSPORT PROCESSES
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