Thursday, November 29, 2007

Movement Across the cell membrane

So in class we learned about diffusion, and the channels within the cell membrane. The definition of Diffusion is the movement of high to low concentration.

The cell membrane is a buffer zone between the internal cell, and the outside of the cell. Cells need to get material in, and wastes out. The cell membrane allows for things such as food, carbohydrates, sugars, proteins, amino acids, lipids, salts, oxygen, and water. The cells need to get wastes such as ammonia, salts, carbon dioxide, water, extra sugar, and other products out of the cell. They are stern. Stern but fair. They must be tough.

As you can see the membrane surrounds the cell, and makes sure only necessary materials get in and out.
Since the middle of the phospholipid bilayer is non polar, only other non-polar molecules can get through, such as Fats and other lipids. Water, other polar molecules, ions, and large molecules cant get though. It's like a hip Hollywood party. Only the coolest celebrities get access, Fats, and other lipids. Polar molecules, ions, and large molecules aren't "cool" enough to get into this party.
Protein Channels make a membrane semi-permeable. Certain channels allow certain membranes across into the cell.

This is just simple diffusion through a membrane channel. When a channel and a molecule are right for each other, the channel moves a specific molecule across the channel into the cell. This doesn't require any energy.
Sometimes high to low concentration just isn't the cool thing to do. Therefore molecules must succumb to peer pressure and go against the concentration gradient. The protein pump, changes its shape to transport the molecules from one side to another. What does this cost you may ask? ATP. Energy. you know.LARGE MOLECULES
Large molecules need loving to. You know what I'm saying. They can move in through vesicles, and vacuoles. There is endocytosis, and exocytosis.

Endocytosis has two parts.

-Phagocytosis is "cellular eating". I mean cells get hungry too. It is a process where cells absorb material ( molecules such as proteins) from the outside by engulfing it with the cell membrane. -pinocytosis is "cellular drinking". is a form of endocytosis in which small particles are brought into the cell suspended within small vesicles which subsequently fuse with lysosomes to hydrolyze, or to break down, the particles.
Exocytosis is the process in which a cell directs secretory vesicles to the cell membrane.
that should be sufficient


ryan g said...

Wow that was a great sherpa report...The best by far.
So I'm repelling down Mount Vesuvius when suddenly I slip, and I start to fall. Just falling, ahh ahh, I'll never forget the terror. When suddenly I realize "Hey, Hansel, haven't you been smoking Peyote for six straight days, and couldn't some of this maybe be in your head?" And it was..I've never even been to mount Vesuvius

mariah:) said...

ok im in high school and im doing a bio project and you guys really need a life not to be mean or any thing but you guys are faggets haha welp bye:)

Darwin Mandelorve said...

Hehe, I'm in honors freshman biology and this is nowhere near the detail we require for our test.

ffs, we get most of what we're doing right now from an AP bio book.