The Cell Membrane Cell Transport The CellPlasma Membrane
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 • The result is a double made primarily of layer called a phospholipids. phospholipid bilayer. • Phospholipids have a hydrophilic, phosphate head and 2 hydrophobic fatty acid tails. • Water molecules surround the membrane.
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) – http: //highered. mcgrawhill. com/sites/0072495855/student_view 0/chapter 2/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 http: //highered. mcgrawhill. com/sites/0072495855/student_view 0/chapter 2/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?
- Slides: 21