The Plasma Membrane PREPARED BY BAHAA KHUDER TAMARA THAMIR BAYDAA ABD ALILAH ENAS AYAD BAYAN HUMADI TAIKA MOAFAK ATTASH

Transcription

1 The Plasma Membrane PREPARED BY BAHAA KHUDER TAMARA THAMIR BAYDAA ABD ALILAH ENAS AYAD BAYAN HUMADI TAIKA MOAFAK ATTASH

2 The Plasma Membrane BAHAA KHUDER

3 The Plasma Membrane the fluid mosaic model (S.J Singer) semi-permeable fluid portion is a double layer of phospholipids, called the phospholipid bilayer

4 The Plasma Membrane Jobs of the cell membrane Isolate the cytoplasm from the external environment Regulate the exchange of substances Communicate with other cells Identification

5 The Plasma Membrane TAMARA THAMIR

6 The Plasma Membrane The Plasma Membrane is also called the Phospholipid bilayer Phospholipids contain a hydrophilic head and a nonpolar hydrophobic tail Hydrogen bonds form between the phospholipid "heads" and the watery environment inside and outside of the cell Hydrophobic interactions force the "tails" to face inward Phospholipids are not bonded to each other, which makes the double layer fluid Cholesterol embedded in the membrane makes it stronger and less fluid

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8 The Plasma Membrane TIAKA MOUFAK

9 Proteins embedded in membrane serve different functions 1. Channel Proteins - form small openings for molecules to difuse through 2. Carrier Proteins- binding site on protein surface "grabs" certain molecules and pulls them into the cell 3. Receptor Proteins - molecular triggers that set off cell responses (such as release of hormones or opening of channel proteins) 4. Cell Recognition Proteins - ID tags, to idenitfy cells to the body's immune system 5. Enzymatic Proteins - carry out metabolic reactions

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11 The Plasma Membrane BAYDAA ABD ALILAH

12 Transport Across Membrane The membrane is differentiallty permeable (also called semipermeable ) - which means Passive Transport Simple Diffusion - water, oxygen and other molecules move from areas of high concentration to areas of low concentration, down a concentration gradient Facilitation Diffusion - diffusion that is assisted by proteins (channel or carrier proteins)

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14 Osmosis - diffusion of water. Salt Sucks Osmosis affects the turgidity of cells, different solution can affect the cells internal water amounts Contractiles Vacuoles are found in freshwater microorganisms - they pump out excess water Turgor pressure occurs in plants cells as their central vacuoles fill with water.

15 The Plasma Membrane BAYAN HUMADI

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17 Active Transport - involves moving molecules "uphill" against the concentration gradient, which requires energy Endocytosis - taking substances into the cell (pinocytosis for water, phagocytosis for solids) Exocytosis - pushing substances out of the cell, such as the removal of waste Sodium-Potassium Pump - pumps out 3 sodiums for ever 2 potassium's taken in against gradient Demo - Starch in the baggie, iodine in the beaker. What happens and why? Observation of elodea cells in salt water. What happens and why?

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19 The Plasma Membrane ENAS AYAD

20 Modification of Cell Sufaces Tight junctions are composed of protein fibers that seal adjacent cells to prevent leakage, something which can be useful in organs such as the bladder and the lining of the digestive tract. Tight junctions literally fuse the cells together forming a sheet of cells restricting molecules to one side of the sheet or the other. Tight junctions can also partition the cells in which they are found. Certain membrane proteins can be restricted to one side of the junction, as well, since the tight junction prevents protein migration within the membrane.

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