Chapter Seven Reading Journal

What is the Membrane composed of?
The main component of the membrane is the Phospolipid bilayer. Phospolipids double up so that their hydrophilic heads are on the outside of the cell and the inside of the cell and their hydrophobic regions are in the middle. Proteins are also major components of the membrane some go through the entire membrane and some are merely attached to the outside. The proteins are useful in identifying other cells and transporting things from one side of the membrane to the other. Cholesterol is also embedded in the membrane to act as a temperature regulator. Carbohydrates and other lipids also attach themselves to the outside of the membrane as markers.

What is the difference between Intergral Proteins and Peripheral proteins?
Intergral proteins go into the core of the membrane some go all the way through to the other side where some just reach the hydrophobic middle. Those that go all the way through have hydrophobic and hydrophilic regions to match up with the corresponding portions of the bilayer. Peripheral Proteins are just attached to the surface of the membrane.

Explain the difference between active and passive transport?
Transport is the way that substances move from one side of the membrane to the other. Passive transport doesn’t require energy from the cell. Forms of passive transport include: diffusion, osmosis, and facilitated diffusion. Active transport goes against the concentration gradient and therefore requires cell energy.

Facts
- Fluid mosaic model is the most common model of the membrane
- One of the most important characteristics of the membrane is that is hydrophobic and hydrophilic
- A membrane that is exposed to colder temperatures will have more unsaturated fatty acids because they are liquid at lower temperatures
- The membrane is selectively permeable
- Transport proteins can aid diffusion without using cell energy




This diagram shows the process of osmosis in which water moves from the side of a membrane with a lower concentration of solute to the side with the higher concentration of solute to balance out the concentrations. It can also be said that water moves from hypotonic solutions to hypertonic solutions. It does this until there is equilibrium (the same concentration on both sides) this is also called an isotonic solution.

Summary:
The membrane maintains fluidity because of the level on unsaturated fatty acids in the phospholipids as well as cholesterol keeping a stable temperature. Proteins also make up a large portion of the membrane they help the cell with transport, provides enzymes, creates signals, and is useful in allowing cells to recognize each other. The membrane is selectively permeable and small nonpolar molecules have the easiest time making it from one side to the other. Thing also cross through processes of diffusion or osmosis or active transport through energy release from the cell. Things can also be transported through endocytosis or exocytosis.