- This is what I learned about......
I learned that membranes are composed of mostly proteins and they control what is allowed in each cell. Phospholipids are hydrophobic at the tails and hydrophillic at the head. The hydrophobic and hydrophillic ends of the structure are fulfilled with the phoshpolipid bilayer. Inside membranes, proteins play a key role since their enzymes carry out important chemical reactions. They also transport substances such as water across the cell membrane. Lastly, i learned that proteins are what help essential molecules cross over into or exit out of a cell.
In section 6.3,I have learned that molecules spreading out to cover an even amount of space is called diffusion. When two substances are in equilibrium, there is the same number of molecules of each substance moving around. A selectively permeable membrane is different than a regular membrane because it only allows certain substances to pass over into its cell. Facilitated transport is when a transport protein opens up the membrane to help certain moleciles get through. This process used on water is called osmosis. It is important for an animals water balance to be isotonic so their red blood cells are shaped normal, not expanded or deflated. However, plant cells thrive on a hypotonic solution because their strong cell walls won't break. An active transport requires the cell to use enegry to move molecules through the membrane. When it comes to moving big molecules into and out of a cell, it requires vesicles to carry this substance around the cell rather than letting it float around freely. When a large molecule is entering a cell (creating a vesicle), it is called endocytosis. The opposite (vesicle forming into the phospholipd membrane again), the process is celled exocytosis.
- What I have found difficult about what I have studied is......
I found the structure of Phospholipids difficult to picture with there only being 2 fatty acids but still connected at the head? I know the picture at the bottom of the page shows it but i don't understand where and how the head connects to both tails. When do Phospholipid bilayers form? Or are they just always present? In membranes, I don't understand where exactly the proteins lie: do they lie within the structure of the phospholipids? When water is being transported through a cell's membrane, does it only have room to tranposrt through the phospholipids, or is their cytoplasm as well for the protein to easily move about.
In section 6.3, I don't understand when something is permeable; does that mean that the 2 substances stay separated like water and oil? I undestand a passive trasport doesn't allow the cell to use energy, but when and what part of a cell other than the membrane use energy? What is a solute concentration (used in hypertonic/hypotonic/isotonic solutions)?
The structure of any molecule is important by telling many of the properties of that special molecule. For example, phospholipids, their two tails and and one head structure determine their hydrophobic/hydrophillic preferences. The head of all phospholipids will be hydrophillic, loving water, and their two tails will each be hydrophobic, hating water. These two qualities are important when it comes to the structure of a phospholipid bilayer in the fact that numerous hydrophillic heads join to form the walls while double that numerous hydrophobic tails are able to stay attatched with the heads blocking out all the water. If this strucutre didnt call for hydrophillic and hydrophobic features, the bilayer couldnt have been created, causing cell membranes to be weak and have trouble limiting the molecules that come in and out of its cell.
