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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