Fluid Mosaic Model Membrane Structure &Processes

Cell Membrane Structure – Current Model Fluid Mosaic Model Contains a double layer of phospholipids Phospholipids arranged with tails pointing in Globular proteins are scattered throughout Proteins have a variety of functions Enzymes Receptor Sites Carriers Cell Recognition

Fluid Mosaic Model

Membranes can be one of four types- permeable impermeable Permeable – allows everything in & out Impermeable - allows nothing in or out Semi-permeable – allows substance in & out based on size Selectively permeable – allows substances in & out based on size and chooses between substances of equal size semi-permeable selectively permeable Definitions:

Which sidewalk is permeable and which sidewalk is impermeable to water?

Gortex raincoats allow air in and keep water out. Use the words in the box at the right to describe how a gortex coat is affected by rain and air. permeable impermeable semi-permeable selectively permeable

Using the definitions of the words below, what type of permeability does cell membranes have? permeable impermeable semi-permeable selectively permeable

Movement Processes: 1. Diffusion -movement of a substance from an area of high concentration to an area of low concentration -passive process – no energy required -used to move respiratory gases oxygen & carbon dioxide

2. Osmosis: -diffusion of water across a cell membrane -movement of water from an area of high concentration (of water) to an area of low concentration (of water) -passive process – no energy required 0.7% salt 0.7% salt Isotonic cell & Bathing Solution -no net movement of water

1% salt 15% salt Hypertonic bathing -more concentrated Hypotonic cell -more water Water moves out Crenation-animal cell shrinks Plasmolysis-plant vacuole shrinks

15% salt 1% salt Hypertonic cell -more concentrated Hypotonic bathing -more water Water moves in Lysis-animal swells to burst Turgor- plant vacuole fills to capacity

Red Blood Cell Plant Cell

Turgor –vacuole fills with water -cell is in a hypotonic solution -chloroplasts move to the edges Plasmolysis -vacuole shrinks -cells in a hypertonic solution -chloroplasts move to the center

3. Facilitated Diffusion movement with the concentration gradient (from high to low) passive process – no energy required requires a protein carrier protein carrier is actually a channel protein (creates a pathway for the substance) used to moves simple sugars (glucose) and amino acids

4. Active Transport requires a protein carrier (channel protein) moves AGAINST the concentration gradient (from low to high) requires energy (ATP) used to conserve and move ions Ex. Calcium, sodium & potassium

5. Exocytosis used to export (release) large molecule requires energy vacuole merges with cell membrane to release a cell product Ex. Goblet cell releases mucus

6. Endocytosis used to bring larger molecules/substances into the cell requires energy form a vacuole from the cell membrane two types a. pinocytosis – “cell drinking” b. phagocytosis – “cell eating”