3.3 Cell Membrane (p. 81)

Transcription

1 Name Bio PreAP/GT 3.3 Cell Membrane (p. 81) Cell Membranes are composed of two phospholipid layers. The cell membrane, or the membrane, forms a boundary between a cell and the outside environment and controls the passage of materials into and out of the cell. A phospholipid molecule has three parts: o Head composed of and Charged [polar] - forms bonds with water o 2 tails Nonpolar attracted to each other and repelled by water o Arranged as a polar on the outside nonpolar in the middle Sketch figure 3.1 in the space provided. Label, proteins, protein channel, phospholipid, cholesterol and carbohydrate chain Embedded in the plasma membrane are cell surface that allow larger materials to pass into and out of the cell. o These proteins are called. describes arrangement of molecules in membrane. o Flexible; not rigid o Membrane behaves as a fluid - membrane allows some, but not all, materials to cross. Chemical signals are transmitted across the cell membrane. protein that detects a signal molecule and performs an action in response. o Recognizes and binds to only certain molecules ligand. o Causes them to change shape. receptor within the cell receptor located in the cell membrane 3.4 Diffusion and Osmosis Diffusion and osmosis are types of passive transport. transport movement of molecules across a cell membrane energy input from the cell o - movement of molecules in a fluid or

2 gas from a region of higher concentration to a region of lower concentration. It take place wherever there is a difference in within the solution. - difference in concentration Particles of a solute and solvent are constantly moving from areas of concentration to areas of concentration. These particles continue to move until the concentrations are equal or reach.... o - diffusion of water molecules from high to low across a semipermeable membrane If a solution has a higher concentration of dissolved particles, then it will have a concentration of water molecules in the same solution the increased pressure that results from an increase of water is called Refer to the figures below to answer the following questions. 1. concentration of sucrose is higher in compartment? 2. concentration of water is higher in compartment? 3. osmosis occurs with movement from _?_ into _?_ 4. diffusion of sucrose will/will not occur. 5. level of column A will increase/ decrease/ remain the same. 6. level of column B will increase/ decrease/ remain the same. *A column of fluid develops which creates a pressure that prevents the solution from increasing its volume further. Osmotic pressure has the effect of pushing water molecules of compartment A back into B. At this point, the number of water molecules moving in and out of compartment A is equal, so exists.

3 A. The cell solution is said to be when there is a concentration of solute in the environment than that in the cell. Thus, the environment solution is said to be. Water will move the cell. This is the shrinking of the cell due to water leaving the cell.... B. The cell solution is said to be when there is a concentration of solute in the environment than that in the cell. Thus, the environment solution is said to be. Water will move the cell. This is the bursting of the cell due to water entering the cell.... C. A cell is said to be when the concentration of solutes in the environment and in the cell are the. Equal amounts of water will move and the cell. o Do you understand Osmosis? Cell (compared to beaker) hypertonic or hypotonic Beaker (compared to cell) hypertonic or hypotonic Which way does the water flow? in or out of cell

4 o - diffusion of molecules across a membrane through transport proteins. Examples: Flasks X, Y, and Z contain solutions with different concentrations of the solute NaCl. Flask X has 0.5% NaCl, Y has 0.9% NaCl, and Z has 1.5% NaCl. Red blood cells (0.9% NaCl) will be placed in each flask. Flask X % of NaCl in flask water will move the cell. Flask Y % of NaCl in flask water will move the cell. Flask Z % of NaCl in flask water will move the cell. 3.5 Active Transport, Endocytosis, and Exocytosis Proteins can transport materials against a concentration gradient. Cells must have a way to maintain concentrations of important food molecules at a level different from the concentration level outside the cell. Active transport uses to transport particles through a membrane the concentration gradient. An example of an active transport channel is the - pump. is required.

5 o is the taking in of particles into a cell by engulfing them in a membrane. o Two types: is the taking in of liquid or dissolved materials. is the taking in of large solid materials. o is the removal of wastes out of a cell by the fusion of a vesicle with the membrane