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Lecture 2

The Cell membrane and Endomembrane system

Histology(MLHS-201)

• Dr. Afaf Mousaad• Department of Medical Laboratory Technology

• Faculty of Allied Medical Sciences

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Learning objectives

Identify examples of the cell structure and explain the functions of each:1. cell membrane2. endoplasmic reticulum,Golgi

apparatus,mitochondria,….3. nucleus

Cell Membrane

•Double layer of

phospholipids &

proteins

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Phospholipids• Polar

– Hydrophylic head– Hydrophobic tail

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Cytoplasm• Viscous fluid containing organelles• components of cytoplasm

– Organelles– Interconnected filaments & fibers – Fluid = cytosol

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Endomembrane system

A series of membranes throughout the

cytoplasm.

1. endoplasmic reticulum

2. Golgi apparatus

3. Lysosomes

4.Mitochondria

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Rough endoplasmic reticulum (rER):-Membranes that create a network of channels throughout the cytoplasm

-Attachment of ribosomes

to the membrane gives a

rough appearance.

-Synthesis of proteins to be

secreted.

Smooth Endoplasmic Reticulum

• No attached ribosomes• Has enzymes that help build molecules

– Carbohydrates– Lipids

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Golgi apparatus

-flattened stacks of

interconnected membranes.

-packaging and & shipping

station of cell,distribute

materials to different parts

of the cell.

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Lysosomes-Membrane bound vesicles containing digestive enzymes to break down macromolecules.-Enfold the substances to be degraded that the cell has engulfed by phagocytosis forming digestive vacuoles, that later migrate toward the plasma membrane fusing with it and liberating (exocytosis) the digested material to the exterior.

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Mitochondria-Present in all types of eukaryotic

cells.

-Contain oxidative metabolic

enzymes for transferring the

energy within macromolecules to

ATP.

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-Surrounded by 2 membranes:-Smooth outer membrane.-Folded inner membrane with layers called cristae.-Matrix is within the inner membrane.-Intermembrane space is located between the two membranes.-Contain their own DNA.

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•A highly specialized organelle , serves as the information center of the cell. •Regulates all cell activities. •Chromatin is DNA in its active form.•It consists of DNA looped around histone protein.

The nucleus

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•Stores the cell's hereditary material DNA, and

coordinates the cell's activities( growth,

metabolism, protein synthesis, and cell division).

•The nucleus also contains one or more nucleoli,

and interchromatin granule clusters.

Nucleolus

• Most cells have 2 or more• Directs synthesis of RNA• Forms ribosomes

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Questions examples

1.What is the cell membrane of the cell? What are its main functions?

• The cell membrane is the outer membrane of the cell, it delimits the cell

• it is selectively permeable, and has an important role for the passage of substances inwards or

outwards.

2. What is the phospholipids that compose the cell membrane?

• two layers of phospholipids form the lipid bilayer with the polar part of the phospholipids pointing to

the exterior of the layer and the non-polar phospholipid chains in the interior.

3.What is the function of Lysosomes ?

• Lysosomes digesting residual substances from the cellular metabolism; and digesting substances

that enter the cell.

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Assignments

Assignment tittles األسم I.D م

Mitochondria

سيحه المسيح عبد اسحاق ابانوب 51012001 1

مؤنس ابراهيم صداق ابراهيم 51012002 2

زيد ابو الغني عبد ماجد ابراهيم 51012003 3

قاسم احمد محمد ابراهيم 51012004 4

الريس احمد السيد احمد 51012005 5

يوسف احمد جمال احمدالدراجينى

51012006 6

الجواد عبد الدين جمال احمد 51012007 7

المقصود عبد احمد حسن احمد 51012008 8