Download - محاضرات الأحياء 7 8-9
Written and Edited by: Fatima Jasim You are not allowed to call things hard; you are allowed only to work hard! Good luck my friends. Dedicated to Section 4 Girls 1434- 2012
Biology, Dr.Faiza’s notes. written and edited by: FatemmaJasim
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Cell membranes and transport process
Introduction:
All cells have plasma membrane.
Eukaryotic cells also have intracellular membrane
that surrounds the cell organelles.
All cell membranes are composed of:
Lipid bilayer
Proteins
Other molecules
Cell membranes can be :
Permeable membrane: everything passes through it.
Impermeable membrane: noting passes through it.
Semi permeable membrane (sensitivity permeable):
same molecules can pass through but not others.
# Plasma Membrane: * definition: is an outer
covering encloses the cell’s internal parts.
- It’s a physical barrier or boundary between the
cytoplasm and extra-cellular fluid (ECF).
The polar head: Is a hydrophilic: toward the
cytoplasm on one side and the tissue fluid on the
other side.
The non-Polar tails: Are hydrophobic (water hating
substances) & they face inward, toward each other.
Behavior of Phospholipids in Water:
How does a fluid cell membrane remain distinct
from its fluid surroundings? Answer: the
phospholipids molecules contain non-polar
Biology, Dr.Faiza’s notes. written and edited by: FatemmaJasim
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(hydrophobic) tails which are form a region that repel
water. *1 They also contain a polar (hydrophilic)
heads which are attracts water (water loving
substances). **2 Therefore, the fluid cell membrane
remains distinct from its fluid surroundings. ***3
The fluid mosaic model
Describes the organization of cell membrane
.Fig. 3.7
A cell like mosaic: is like a fluid, fluid mosaic
model.
A cell membrane is fluid: because movement of
molecules in the membrane: movement of lipid
molecules (they spin around their axis).
Their tails flex back and frost *wiggle*
Also, some proteins molecules shift in their
positions & change their shapes on the
membrane.
Important of Fluidity
Helps in the fusion of membrane with each other.
Helps activity of membrane enzymes
Helps protein transport and function
Cell membrane:
1. Are embedded in or attached a lipid bilayer.
2. Carry out most of cell membranes’
functions.
3. Many of these proteins are enzymes.
4. Other membrane proteins serve a range of
functions.
Biology, Dr.Faiza’s notes. written and edited by: FatemmaJasim
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Types of membranes: Fig 3.7
Transport Proteins:
• involved in passive or active transport of
substances across the lipid bilayer of plasma
membrane
• Solutes on one side of the membrane pass through
te proteins interior to the other side.
• Transport Proteins.
Channel Proteins: Is type of transport protein that serve
as a pore through which ions or other water-soluble
substance move across the plasma membrane. ( they can
be gated or non-gated).
Receptor proteins: Identify a cell as self
They attack invading bacteria cells but not their
own cells.
Adenosine Proteins : Help cells stick to one another
to form tissue.
First advice: Be strong
Biology, Dr.Faiza’s notes. written and edited by: FatemmaJasim
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Some terms:
Solution: (solute + solvent )
Solute: substances dissolve in solvent
Solvent: the dissolving medium.
Concentration: number of molecules in specific regions.
Gradient: difference in concentration between two regions.
Concentration gradient: a difference in the number of molecule of
ions of substances in two nearby regions.
Transport process: Carries substances to and away from the
cells across the cell membrane by:
1) Diffusion: movement of molecules from a region of
higher concentration to a region of lower concentration until
they are evenly distributed.
* It’s down a concentration gradient.
*Doesn’t require ATP energy ( passive transport)
Figure 3.16
Molecules that move in by diffusion: O2\Co2\small nonpolar
molecules (lipid soluble)\some water.
Factors influencing diffusion:
The size of molecule.
Temperature
Steepness of the diffison gradients
Diffusion
Osmosis
Faciliated Diffusion
active transport
endocytosis
exocytosis
Biology, Dr.Faiza’s notes. written and edited by: FatemmaJasim
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Electronic & pressure gradients
2) Osmosis: is the diffusion of water molecules through a
sensitivity permeable membrane from an area of higher water
concentration to an area of lower water concentration. (passive
transport). Fig. 3.17
Tonicity: refers to relative concentration of solutes in two
fluids.
When solute concentrations in the fluids on either side
of a cell membrane are the same to fluids are isotonic
and there is no net flow of water in either direction
across the membrane.
Normally, the fluid inside the cells and tissue fluid are
isotonic.
When the solute concentration are not equal.
One fluid is hypotonic it as fewer solutes
The other is hypertonic has more solutes.
Tonicity determines the direction of water movement across
membrane.
Water diffusion from a hypotonic to hypertonic
fluid.
Isotonic solution: equal solute, equal water.
Hypotonic solution: less solute, more water.
Hypertonic solution : more solute, less water.
Effects of Tonicity on RBCS:
- If red blood cells are placed in isotonic solution no net
change in water movement or cell shape.
- Hypotonic solution water diffusion in the cells swell \may
burst.
- Hypertonic solution: water diffusion out, the cell shrinks.
- Figure 3.18
Biology, Dr.Faiza’s notes. written and edited by: FatemmaJasim
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3) Facilitated Diffusion: o It is down a concentration gradient – passive transport-
o Requires passive transporter proteins
o Does not require energy
o E.g.: Glucose or amino acids from blood into a cell. Fig:
3.19B
o A solute molecule binds a passive transporter protein that
releases it on the opposite side of the membrane.
o Binding causes the protein to change shape.
Active transport:
Pumping of substances across a cell membrane
against concentration gradients.
Requires energy from ATP
Requires Active transport
E.g.: in nerve and muscle cell.Na+,K+, Ca++ pump.
Exocytosis & Endocytosis: - Move large molecules or participles in bulk across the
plasma membrane.
- Require energy. ****** Figure 3.20
Bulk Transport :
Exocytosis
Endocytosis
Biology, Dr.Faiza’s notes. written and edited by: FatemmaJasim
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Endocytosis:
* It is the process by which a cell takes in a large
molecule or participle by eating a vesicle that
encloses it and moves it into the cell cytoplasm.
* E.g.: taken of bacteria by WBC (white blood
cells) phagocytosis (cell eating).
Exocytosis:
It is the process in which a vesicle encloses
and moves a large molecule or participle to the
cell surface and expels it out.
E.g.: secretion of protein and hormones.
How substances cross membrane?
None-polar substances/polar substances
What substances can cross directly?
Molecules O2/Co2/water.
Second Advice: Focus on your dream!
Biology, Dr.Faiza’s notes. written and edited by: FatemmaJasim
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Tissues Bio:8
A tissue is a group of cells and intercellular substance
Matrix that function together in one or more
specialized tasks.
Matrix binds the cells together.
It’s produced by the cells themselves.
Study of tissues is called “ Histology” : it deals with
the microscopic study of: different types,
arrangement, and specialized of cells.
Types of tissues:
First: Epithelial tissues
1) Arise from any of three primary gem layers:
Ectoderm- Mesoderm- Endoderm
2) Have little matrix
3) Have sheets like layers of the cell.
4) One of its surfaces faces an internal body fluid or
outside environment
5) The other surface rests on a Basement
Membrane between it and underlying tissues.
Epithelial
muscle
Connective
Nervous
Biology, Dr.Faiza’s notes. written and edited by: FatemmaJasim
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Basement Membrane:
1) Non-cellular.
2) Function: supportive ) دعامة (
3) Separates epithelium from connective tissues.
4) Have no blood vessels.
5) They cover the body outer surfaces like Skin.
6) They line internal cavities and tubes. التجاويف(
Like blood vessels stomach and small واألنانبيب(.
intestine. )المعدة واألمعاء الدقيقة (
7) They have the ability of multiplication to
regenerate the cells.
8) Form epithelial cells are ciliated for move the
mucus)المخاط( , upper airways )القصبة الهوائية(, and
oviducts )قناة فالوب( .
9) Absorption )عملية اإلمتصاص( in (lining kidney,
small intense).
10) All glands )الغدد( develp from epithelial
tissues. E.X: Exocrine glands) الغدد غير الّصماء ( and
Endocrine Glands ) غدد صماء (.
Exocrine glands: releases substances through a
duct)ممر( or tubes. Ex: digestive system
enzymes, mucus, saliva )اللعاب ( .
Endocrine Glands:
Don’t realse substances through a duct or tubes.
They make hormones that are released directly
into fluid outside the gland.
Biology, Dr.Faiza’s notes. written and edited by: FatemmaJasim
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Types of Epithelial tissues:
Classified according to their:
Structure/shape/arrangement
Function
1) Structure of Epithelial:
Types of simple Epithelium : Figure 4.1 & table 4.1
Structure
Simple epithelum compound/stratfied
Epithelum
Biology, Dr.Faiza’s notes. written and edited by: FatemmaJasim
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Function: diffusion, secretion, absorption and
filtering substances.
Stratified Epithelium: Has more than one layer of cells.
Protect underlying tissues.
Types: squamous, cubical, and columnar.
Pseudo compound Epithelium)النسيج الكاذب(
- Single layers of columnar cells but appears 2
layers.
- Some cells are shorter than others
- Nucleous at different positions
- Longer cells have cilia
- Location: nose, throat, nasal passage, sinuses,
tracheas, male gentical ducts.
- Function: trap dirt, micro organsims Figure 4.1
Third Advice: Do your best to be the best
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