Cell Boundaries Keeping the world out of our cell

What are the boundaries? 2 TYPES- cell membrane & cell wall All cells are surrounded by a thin, flexible barrier known as the cell membrane. Many cells also produce a strong supporting layer around the membrane known as a cell wall.

Cell Membrane What does it do??? –The cell membrane regulates what comes in and out of the cell. The composition of nearly all cell membranes is a double-layered sheet called a lipid bilayer. –Its made of lipids and it has two layers (bilayer) Called SELECTIVELY PERMEABLE This means some things come in and other things are kept out. Usually bigger substances have to enter through a special protein doorway

This is a lipid bilayer

Cell Wall Why do we need a wall in the first place? –The main function of the cell wall is to provide support and protection for the cell. Hmmm… Cell walls are found in plants, algae, fungi, and many prokaryotes. The cell wall lies outside the cell membrane. Most cell walls are porous enough to allow water, oxygen, carbon dioxide, and certain other substances to pass through easily

Cellular Transport Moving things on a cellular level

Passive Transport Two types –Diffusion –Osmosis How is that possible? The cell membrane regulates movement of dissolved molecules from the liquid on one side of the membrane to the liquid on the other side.

Diffusion Particles move from an area of HIGH concentration to LOW concentration –This process is called diffusion. –When the concentration of the solute is the same throughout a system, the system has reached equilibrium (aka equal level) AND DON’T FORGET NO ENERGY IS USED!!!

Diffusion at its best…. Remember High Concentration to Low Concentration

Facilitated Diffusion DIFFUSION with HELP Cell membranes have protein channels that act as carriers, making it easy for BIG molecules to cross. Hundreds of different protein channels have been found that allow particular substances to cross different membranes.

Osmosis Osmosis is the diffusion of water (HIGH to LOW) through a selectively permeable membrane.

Hypo vs. Hyper Water tends to diffuse from a highly concentrated region to a less concentrated region. If you compare two solutions, the more concentrated solution is hypertonic (“above strength”). The more dilute solution is hypotonic (“below strength”).

Isotonic Oh the bliss… When concentrations of solutions are the same on both sides of a membrane, the solutions are isotonic (“same strength”). But always remember…is the water or the particles what’s moving??? THE WATER

Active Transport Sometimes cells move materials in the opposite direction from which the materials would normally move (low to high) This process is known as active transport. Active transport requires energy.

Endocytosis and Exocytosis – Endocytosis process of taking material into the cell by means of infoldings, or pockets, of the cell membrane. –TWO KINDS- Phagocytosis and Pinocytosis »Phagocytosis- surround and package »Pinocytosis- surround and pinch off –Exocytosis Forces contents out of the cell