The Cell Membrane Cell Transport

The Cell(Plasma) Membrane A thin flexible layer that surrounds all cells and regulates what enters and leaves the cytoplasm of the cell.

Parts of the Cell Membrane The cell membrane is made primarily of phospholipids. Phospholipids have a hydrophilic, phosphate head and 2 hydrophobic fatty acid tails. Water molecules surround the membrane. The result is a double layer called a phospholipid bilayer.

Parts of the Cell Membrane Cholesterol is needed in animal cell membranes to prevent the body from freezing at low temperatures. It also makes the membrane more firm. The arrangement of phospholipids in the bilayer makes the cell membrane selectively permeable.

Fluid Mosaic Model

Parts of the Cell Membrane Integral Proteins-exposed to the interior and exterior of the membrane. They detect environmental signals and transmit them to the inside of the cell. Usually has carbohydrates attached. –These carbohydrates acts as labels on the surface. Some labels help cells recognize each other and stick together. –Unfortunately, viruses can use these labels as docks for entering and infecting cells.

Parts of the Cell Membrane Peripheral Proteins-not embedded in the membrane. Transport Proteins- helps substances move across cell membrane.

Fluid Mosaic Model Scientists describe the cell membrane as a fluid mosaic. –The fluid mosaic states that the phospholipid bilayer behaves like a fluid more than a solid.

What needs to move into and out of the cell? Oxygen, Water, Nutrients need to enter the cell. Carbon Dioxide, other wastes, and proteins need to leave the cell.

Where would you rather be traveling on the road? We would want to get away from the high concentration of cars, to a more open or less concentrated road.

Types of Cell Transport Diffusion- Particles move from an area of high to low concentration without using any of the cell’s energy »A type of passive transport (No energy required) »Diffusion will eventually cause the molecules to be in equilibrium. »Even after equilibrium is reached, the movement of molecules continue to move. Diffusion

Osmosis The process by which water molecules diffuse across a membrane from an area of high concentration to low concentration. –Energy is not needed for osmosis to occur. (Passive Transport) – hill.com/sites/ /student_view0/chapter2/animation__how_os mosis_works.htmlhttp://highered.mcgraw- hill.com/sites/ /student_view0/chapter2/animation__how_os mosis_works.html

Concentration Gradient- the difference in the concentration from one point to another.

What happens to a cell in different situations?

Plasmolysis -the shrinking or contraction of a cell. –What type of solution would the cell be in for this to occur? Cytolysis- the bursting of cells. –What type of solution would this cell be in for this to occur?

Finding Nemo Saltwater Fish vs. Freshwater Fish Why do you think that some fish cannot survive in freshwater?

Facilitated Diffusion-(passive) A protein channel in the cell membrane helps a molecule into or out of the cell. Facilitated Diffusion 2 hill.com/sites/ /student_view0/chapter2/animation__how_facilitated_diffusion_works.ht mlhttp://highered.mcgraw- hill.com/sites/ /student_view0/chapter2/animation__how_facilitated_diffusion_works.ht ml

Active Transport Particles move from LOW to HIGH concentration (against the concentration gradient) with the use of ENERGY (ATP). Active Transport

Types of Active Transport Endocytosis – Particles enter the cell –Pinocytosis-the transport of solutes or fluids –Phagocytosis-the movement of large particles or whole cells.(food) Exocytosis – Particles are released or exits the cell

The membrane is Semi-Permeable (Only some things can enter the cell) Small polar and non-polar molecules can enter through the cell membrane. –Water, Oxygen, Carbon Dioxide Large polar molecules cannot make it through the “water hating” areas. They need help to enter the cell. –ions Large non-polar molecules also need help to enter the cell. –Glucose Semi-Permeable Animation

Where salt goes, water flows! If there is a higher concentration of salt in one area, water will flow toward the higher salt concentration. (Toward the area where there is less water). Why do you feel thirsty when you eat french fries?