2. Structure of cell membrane & transmembrae movements of substances

Compiled by: Prof.Anwar-AIKTC-SoP

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2. Structure of cell membrane and trans- membrane movement of substances

Presented by: Prof.Mirza Anwar BaigAnjuman-I-Islam's Kalsekar Technical Campus

School of Pharmacy,New Pavel,Navi Mumbai,Maharashtra


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Topic learning outcomes:

• Describe the structure of the cell membrane.

• Compare and contrast active, passive and bulk transport of substances across cell membranes.


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Structure of a simple cell:


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Plasma membrane:

• The plasma membrane, a flexible yet sturdy barrier that surrounds and contains the cytoplasm of a cell, is best described by using a structural model called the fluid mosaic model.

• Consist of following parts– Lipid Bilayer• Phospholipids (75%)

• Cholesterol (about 20%)

• Glycolipids (about 5%),


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Functions of membrane proteins:


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Functions of membrane proteins:


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Membrane fluidity:• Membranes are fluid structures; that is, most of the

membrane lipids and many of the membrane proteins easily rotate and move sideways in their own half of the bilayer.

• Membrane fluidity is an excellent compromise for the cell; rigid membrane would lack mobility, and a completely fluid membrane would lack the structural organization and mechanical support required by the cell.

• Membrane fluidity allows interactions to occur within the plasma membrane, such as the assembly of membrane proteins. It also enables the movement of the membrane components responsible for cellular processes such as cell movement, growth, division, and secretion, and the formation of cellular junctions.

• Fluidity allows the lipid bilayer to self-seal if torn or punctured.


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Transport across the cell membrane:

1. Passive process • Simple diffusion

• Facilitated diffusion

• Osmosis

2. Active Process•Active transport

• Primary

• Secondary

•Transport in vesicle• Endocytosis

• Exocytosis

• Transcytosis


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Simple diffusion:


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Facilitated diffusion:


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Hyptonic and Hypertonic solutions:


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2. Active transportPRIMARY ACTIVE TRANSPORT:• In primary active transport,energy derived from hydrolysis of

ATP changes the shape of a carrier protein.• A typical body cell expends about 40% of the ATP it generates

on primary active transport. • Example, the poison cyanide—are lethal because they shut down

active transport in cells throughout the body.• The most prevalent primary active transport mechanism expels

sodium ions (Na) from cells and brings potassium ions(K) in.


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3.Transport in Vesicles

1. ENDOCYTOSIS:• Receptor-mediated endocytosis,

• Phagocytosis, and

• Bulk-phase endocytosis.

2. EXOCYTOSIS

3. TRANSCYTOSIS


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Receptor-mediated endocytosis, & Phagocytosis


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Bulk phase endocytosis:


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2. Exocytosis:


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3. TRANSCYTOSIS

• Transport in vesicles may also be used to suc-cessively move a substance into, across, and out of a cell.

• In this active process, called transcytosis, vesicles undergo endocytosis on one side of a cell, move across the cell, and then undergo exocytosis on the opposite side.


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THANK YOU

Education

2. Structure of cell membrane & transmembrae movements of substances