Chapt 03

GENERAL BIOLOGY

SCHOOL OF MLTFACULTY OF HEALTH SCIENCE

PREPARED BY:MANEGA

HDL 121

CELL MEMBRANE TRANSPORTATION


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Chapter 3 : Cell Membrane Transportation

Course Purpose

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This course introduces animal cells based on structure, characteristics, functions and cellular division. It also emphasises the theory of inheritance including the structure

and role gene, DNA, and chromosome.


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Topic Outlines

3.1 Movement of molecules in & out of cells3.1.1 Types of movement

3.2 Passive transport3.2.1Definition3.2.2 Types of passive transport, principles, example

3.3 Active Transport 3.3.1 Principles & example of active transport

3.4 Vesicular transport 3.4.1 Principles & example of active transport

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Course Objectives

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To develop understanding of general biology and genetics basic principles and definition.

To understand the scope of biology and human genetics which includes the study of cell, structure of cell, division of cells, genetic materials, mutation and common genetic condition.

To acquire knowledge according diseases caused by genetic mutation.

To understand basic techniques involved in biology laboratory.To understand laboratory hazards and step to ensure safety in

biology procedure.


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Learning Outcomes

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After completing this lecture, students will be able to:(a) List out the types of cell membrane’s transport(b) Describe passive transport Diffusion Osmosis(c) Explain active transport Sodium/Potassium Pump(d) Summarize vesicular transport Exocytosis


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Sub Topic 3.1 Movement of molecules in & out of cells

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Types of movementPassive Transport

Active Transport

Vascular Transport(a) Endocytosis(b) Exocytosis


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Chapter 3: Cell Membrane Transportation

Sub Topic 3.2.1/3.2.2 : Passive Transport/Definition

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Does not require energy (ATP) from the cell

Example include - diffusion of O2 & CO2 - osmosis - Facilitated diffusion


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Sub Topic 3.2.1/3.2.2 : Passive Transport/Definition

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Characteristics


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Sub Topic 3.2.2 Types of passive transport, principles, example

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Net movement of solutes (molecule, ions or atoms) from a region of higher concentration to a region of lower concentration (down a concentration gradient)

Diffusion


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The rate of diffusion depends on: Concentration gradient (difference of concentration between the

two areas)Distance of diffusionArea of diffusion Size of diffusing molecules


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Facilitated Diffusion

Movement of solutes across a membrane, with the help of transport proteins.

Follows the concentration gradient & no energy is needed


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Osmosis

Passive movement of water across a the fine pores of the semi-permeable membrane

Spontaneous, as a result of a downhill energy system called ‘water potential’

Water moves from an area of higher potential to an area of lower water potential

Water potential = the tendency for water molecules to enter or leave a solution by osmosis


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A high concentration of waterA lower concentration of water


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Dissolving solute molecules in pure water will reduce the water potential. Why?

Example of osmosisHypotonic medium – a dilute solution, with a higher water

concentration than the cell – the cell will gain water through osmosis

Isotonic medium – a solution with exactly the same water concentration as the cell – there will be no net movement of water across the cell membrane

Hypertonic medium – a concentrated solution, with a lower water concentration if compared with the cell – the cell will loose water by osmosis


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Sub Topic 3.3 : Active Transport

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The movement of substances across membranes, which requires energy in the form of ATP.

From an area of low concentration to an area of high concentration

Involves carrier proteins in membranesThe cell uses active transport in three situations:(a) when a particle is going from low to high concentration(b) when particles need help entering the membrane because they are selectively impermeable(c) when very large particles enter and exit the cell


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Sub Topic 3.3 : Active Transport

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Characteristics

Carrier proteins or channel protein is requiredEach type of carrier protein is specific for one type of substance

to carryIt will go against concentration gradientThe process will only stop when there is no more of the

substance to transport


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Sub Topic 3.3.1: Principles & example of active transport

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Sodium Potassium Pump

The sodium/potassium pump must break ATP down into ADP in order to pump three ions sodium outside the cell, while it pumps two potassium ions into the cell. The ATP phosphorylates (adds a phosphate to) the membrane protein as it binds to the sodium and breaks down, and it dephosphorylates the protein as it binds with the potassium

Cellular respiration must occur to add the phosphate back to ADP, thus restoring the ATP


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In order to maintain the cell potential, cells must keep a low concentration of sodium ions & high levels of potassium ions within the cell (intracellular)

Outside the cells (extracellular), the are high concentrations of sodium & low concentrations of potassium

diffusion occurs through ion channels in the plasma membrane

Eg. Neuron & muscle


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Sub Topic 3.4: Vesicular Transport

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Cytosis – movement with vesicles @ vacuoles

Endocytosis(a) Phagocytosis(b) Pinocytosis

Exocytosis

Vesicle: relatively small intracellular, membrane-enclosed sac that stores or transports substances


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Sub Topic 3.4.1:Principles & example of active transport

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Endocytosis

Uptake of substances by cell en mass or in bulk in the form of vesicleTwo types:

(a) phagocytosis(b) Pinocytosis


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Phagocytosis

Cellular eatingSolid substances or whole organisms are brought inside the cell

by invagination (an infolding of the cell membrane)A vacuole is formed, the inner surface of which is derived from

the outer surface of the cell surface membraneEg. Amoeba, white blood cells (phagocytes) perform

phagocytosis


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Phagocytosis


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Pinocytosis


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Exocytosis

Reverse of endocytosis in which the cell egests or secretes substances

Transport of materials out of a cellMaterials to be exported must first be enclosed in a

membrane vesicle, usually from the rough endoplasmic reticulum & Golgi apparatus eg. hormones & digestive enzymes & residue indigested microorganisms from the intracellular digestion by lysosomes

Eg. Secretion of mucus or hormones


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Exocytosis

Hormones & digestive enzymes are secreted by exocytosis from the secretory cells of the intestine & endocrine glands. Vesicles & vacuoles move to the cell surface membrane, fuse with it & release their contents to the outside


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Summary

Method Uses energy Uses protein Specific Controllable

Diffusion None No No No

Facilitated diffusion

None Yes Yes Yes

Osmosis None No Yes No

Active transport

Yes Yes Yes Yes

Endocytosis Yes No Yes Yes

Exocytosis Yes No Yes Yes

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Chapt 03

Technology