Cell Membranes Chapter 3.3

Phospholipid Made up of 3 things: Charged phosphate group Glycerol Two fatty acid chains

Phospholipid Bilayer Cell membrane (AKA plasma membrane) is the boundary between the inside and outside of a cell. It is made up of two layers of phospholipids.

The heads of the phospholipids are hydrophilic because they are polar The heads of the phospholipids are hydrophilic because they are polar. The insides and outsides of cells are filled with water, so this makes sense. The nonpolar tails turn away from the water and actually act as a barrier to water just freely moving in/out of cells. Remember! Hydrophobic = Water hating Hydrophilic = Water loving

Important Macromolecules Lipids: (other than the obvious phospholipids) Cholesterol strengthen cell membrane. Proteins: Cytoskeleton (interior of cell) Transporting materials (transport / channel proteins) Carbohydrates: Bond onto the outside of cells to act as identification tags for cell recognition purposes.

Fluid Mosaic Model Description of the cell that is both fluid (free moving) and has many parts. This model explains why it is considered to be “selectively permeable” or “semi-permeable” This allows some things, but not all, to pass through it.

Chemical Signals Receptors are proteins that detect signal molecules and performs actions in response. This is how cells communicate with the rest of your body. The molecules that attach to the receptors are called ligands. There are two kinds of receptors: Intracellular and membrane.

Diffusion and Osmosis Chapter 3.4

The Triangle of Love Your new best friend © Concentration Gradient: Number of solutes in relation to the solution itself. Passive (Down) No Energy Required HIGH LOW Active (Up) Energy Required!

Passive Transport The cell always has things moving in and out of it. If it always used energy to do this, it would need a lot of energy. Passive Transport Process of moving things in and out of a cell without using energy. Both osmosis and diffusion use this type of transport. Passive (Down)

Diffusion Movement of materials from high concentration areas to lower concentration areas. This means it moves DOWN the concentration gradient. This means substances will even out over time. Passive (Down)

Passive (Down)

Osmosis This is diffusion, but it only focuses on how water moves. Nothing else. Moves from area of higher concentration of water to area of lower concentration of water. So remember: water is usually the solvent. If you have a lot of a solute, then you will have less solvent. This is a higher concentration. Passive (Down)

Passive (Down)

Effects of osmosis Hypertonic Higher concentration of solute outside of cell means water will move out. Cell shrivels. (crenation) Isotonic Cell has same amount of water and solute, so equal exchange happens. Cell stays normal Hypotonic Higher concentration of solute inside of cell means water will move in. Cell bursts. (lysis)

Hypotonic vs. Hypertonic

Facilitated diffusion This is when a protein is used to help move things across the cell membrane. This does not use energy. Usually there are special proteins to help certain materials cross. Still moves from high to low concentration. Passive (Down)

Active Transport Chapter 3.5

Active Transport When materials are transported into an area of low concentration from an area of high concentration. This moves AGAINST or UP the concentration gradient. Energy is used in this process. (ATP is the energy source) This is occurring all over your body at great speed. Active (Up)

Endocytosis This is the process of a cell taking liquids or large molecules by engulfing them in a membrane. The cell membrane folds inward and forms a vesicle. Then the vesicle is connected to a lysosome to break down the new material. Endo = “within” “inner” or “absorbing” Active (Up)

Phagocytosis and Pinocytosis Phagocytosis: “eats” large molecules. Pinocytosis: “drink” smaller molecules. Important in the immune system and nerve signals. After the extracellular material is “hugged” and surrounded by the outcropping of membrane, it is pulled into the cell. (This is usually when digestive enzymes in lysosomes can do their job) Active (Up)

Active (Up)

Exocytosis The release of substances out of a cell by the combining of a vesicle and the cell membrane. It is the reverse of what you would see in endocytosis. Every muscle movement depends on these two processes. Exo = “outside” or “out of” Active (Up)