membrane and transport cell

MEMBRANE AND TRANSPORTATION OF CELL

Siti Hildani Thaib,dr.,MKes.Department of Medical Bology and Andrology Faculty of Medicine Sriwijaya University

SHT - BLOK V MEMBRANE AND TRANSPORTATION

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LEARNING OBJECTIVES

Student be able to know and understand to :

The structure of membrane, The cell mechnisme of transportation Its relation to some condition of

health problems


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LEARNING CONTENTS

1.1. Introduction,Introduction,

2.2. Cell MembraneCell Membrane

3.3. TransportationTransportation

3.1. Passive, and3.1. Passive, and

3.2. Active 3.2. Active


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HYDROLOGIC CYCLEHYDROLOGIC CYCLE

1. INTRODUCTION1. INTRODUCTION


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1. INTRODUCTION1. INTRODUCTION

Water potential is the tendency of water to move from an area of higher concentration to one of lower concentration.

Energy exists in two forms: potential and kinetic. Water molecules move according to differences in

potential energy between where they are and where they are going. Gravity and pressure are two enabling forces for this movement. These forces also operate in the hydrologic (water) cycle.

Remember in the hydrologic cycle that water runs downhill (likewise it falls from the sky, to get into the sky it must be acted on by the sun and evaporated, thus needing energy input to power the cycle).


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2. CELL MEMBRANE2. CELL MEMBRANE

Cell membranes act as barriers to most, but not all, molecules. Development of a cell membrane that could allow some materials to pass while constraining the movement of other molecules was a major step in the evolution of the cell.

Cell membranes are differentially (or semi-) permeable barriers separating the inner cellular environment from the outer cellular (or external) environment.


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The cell membrane or plasma membrane or plasmalemma, is a semipermeable lipid bilayer common to all living cells

It contains a variety of biological molecules, primarily proteins and lipids, which are involved in a vast array of cellular processes

It also serves as the attachment point for both the intracellular cytoskeleton and, if present, the cell wall.



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The cell membrane surrounds the cytoplasm of a cell and physically separates the intracellular components from the extracellular environment, thereby serving a mechanical function similar to that of skin.

This barrier is able to regulate what enters and exits the cell as it is selectively permeable - cells require a variety of substances to survive and the cell membrane serves as "gatekeeper" to what, and how much, enters and exits



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The movement of substances across the membrane can be either passive, occurring without the input of cellular energy, or active, requiring the cell to expend energy moving it across the membrane.

Specific proteins embedded in the cell membrane act as molecular signals which allow cells to communicate with each other.



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• Protein receptors are found ubiquitously and Protein receptors are found ubiquitously and function to receive signals from both the function to receive signals from both the environment and other cells. These signals are environment and other cells. These signals are transducedtransduced into a form which the cell can use into a form which the cell can use to directly effect a response. to directly effect a response.

• Other proteins on the surface of the cell Other proteins on the surface of the cell membrane serve as "markers" which identify a membrane serve as "markers" which identify a cell to other cells.The interaction of these cell to other cells.The interaction of these markers with their respective receptors forms markers with their respective receptors forms the basis of cell-cell interaction in the immune the basis of cell-cell interaction in the immune system.system.



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2. CELL MEMBRANE


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2. SEL/PLASMA MEMBRANE


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3.1.Passive Transportation

Types of passive Transportation: Diffussion Osmosis


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3.1.1 DIFFUSSION3.1.1 DIFFUSSION

Diffusion :1. Simple Diffusion2. Facilitated Diffusion


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1. SIMPLE DIFFUSION1. SIMPLE DIFFUSION

Simple diffusion means that the molecules can pass directly through the membrane. Diffusion is always down a concentration gradient. This limits the maximum possible concentration of the molecule inside the cell (or outside the cell if it is a waste product). The effectiveness of diffusion is also limited by the diffusion rate of the molecule.

Therefore, though diffusion is an effective enough transport mechanism for some substances (such as H2O), the cell must utilize other mechanisms for many of its transport needs.


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2. FACILITATED DIFFUSION2. FACILITATED DIFFUSION

Facillitated Diffusion Facillitated diffusion utilizes membrane protein

channels to allow charged molecules (which otherwise could not diffuse across the cell membrane) to freely diffuse in a nd out of the cell. These channels comes into greatest use with small ions like K+, Na+, and Cl-. The speed of facillitated transport is limited by the number of protein channels available, whereas the speed of diffusion is dependent only on the concentration gradient.


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diffusion - movement of molecules from a region of higher

concentration to a region of lower concentration.


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DIFFUSION = PASSIVE TRANSPORTDIFFUSION = PASSIVE TRANSPORT


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2. OSMOSIS2. OSMOSIS

Osmosis And Water Balance water flows smoothly across cell

membranes without needing any carrier = osmosis. Other polar or charged molecules (unless lipid soluble).

Three situations can result from water movement. Isotonic environment Hypotonic environment Hypertonic environment


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2. OSMOSIS2. OSMOSIS

Isotonic environment. Water concentration outside = water conc.

inside cell. Since most cells contain about 0.9% dissolved

salts + solutes, isotonic environments must contain 0.9% salt. In this situation, water flow out = water flow in. For human cells, this is desirable state.

Laboratory and clinical workers often use Ringer's solution to bathe exposed tissues, provide isotonic environment.


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2. OSMOSIS2. OSMOSIS Hypotonic environment. Water concentration outside cell is higher (e.g. pure

water) than inside cell. Or, solute concentration outside cell is lower than inside cell. Result: water moves in at greater rate that moves

out. 2 possible results:

if cell lacks a wall, will swell up. Can cause lysis (swelling leading to breakage) if no way to remove excess water (e.g. in blood cells). Freshwater protists (e.g. paramecium) have contractile vacuoles to pump water back out, prevent lysis.

if cell has a wall, water pressure will push membrane tightly against wall, lead to turgor. This is desirable state for walled cells.


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2. OSMOSIS2. OSMOSIS Hypertonic environment. Water concentration

outside cell is lower (e.g. brine, syrup) than inside cell. Or, solute concentration outside cell is higher than inside cell. Result: water moves out at greater rate that

moves in. 2 possible results:

if cell lacks a wall, will shrivel up like a raisin. Causes crenation in blood cells. Cells stop metabolizing, but not immediately killed. Can restore activity by placing back in isotonic environment.

if cell has a wall, membrane will shrink away from wall as water leaves cell, rigid wall remains where it is, leads to plasmolysis. This is undesirable state for walled cells, cells stop metabolizing.


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3.2. ACTIVE TRANSPORT3.2. ACTIVE TRANSPORT

Active transport involves the use of proteins that don't just passively facilitate the transport of substances across the cell membrane, but require the use of cellular energy(usually ATP) to actively pump substances into or out of the cell. The animation represents the action of a sodium-potassium pump found in the cell membrane of neurons. This protein pumps sodium ions(red squares) from the inside to the outside of the neuron and pumps potassium ions(green squares)in the opposite direction. Notice the cell must use ATP(purple) for this process. As the sodium fits onto a site on the protein, a phosphate is transferred to the protein providing energy to kick the sodium ion to the outside and the potassium ion to the inside. This process sets up a high concentration of sodium ions outside the cell and a high concentration of potassim ions inside the cell. This concentration difference across the membrane is important for the generation of thenerve impulses by which neurons transmit information from on end of the neuron to the other. So even if you're zoned out in front of the tube your neurons are actively working to maintain this concentration difference...just in case they nave to send any information.


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3.2. ACTIVE TRANSPORT 3.2. ACTIVE TRANSPORT

2 TYPES : Endocytosis

(Phagocytosis , picnocytosis) Exocytosis


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VESICLE MEDIATED TRANSPORTVESICLE MEDIATED TRANSPORT


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ENDOCYTOSISENDOCYTOSIS


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Conclusion

Membrane cell is a divider between inner and outer cell

Membrane cell acts as transportation place from inner to outer cell and vice versa.


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membrane and transport cell

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