The Plasma Membrane is selectively permeable:

1. Nonpolar molecules, such as hydrocarbons, carbon dioxide, and oxygen, are all hydrophobic. These can dissolve in the lipid bilayer and cross. 2. Ions and polar molecules cannot pass through 3. Water can pass slowly 4. Charged atoms or molecules are less likely to penetrate

The Plasma Membrane is Fluid:

1. Individual phospholipids and unanchored proteins can move through the membrane 2. Saturated Fatty acids make the membrane less fluid than unsaturated fatty acids. 3. Warm temperatures make the membrane more fluid than cold temperatures. 4. Lipid composition of the ER membrane, Golgi, and plasma membrane is all distinct. Composition affects fluidity, thickness, and shape of membrane.

The Plasma Membrane has a double membrane/bilayer:

Due to the chemistry of phospholipids, the tails of phospholipids do not want to interact with water. The tails will arrange themselves to be out of contact with water, while the heads are in contact.

The Plasma Membrane has a fluid mosaic model:

1. The currently accepted model of the arrangement of molecules in the plasma membrane. 2. The membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids. 3. Includes integral proteins, glycolipids, peripheral proteins, glycoproteins, cholesterol, and the cytoskeleton.

What are the 4 components of the cell membrane?

1. Phospholipid Bilayer: flexible matrix, barrier to permeability 2. Transmembrane proteins: integral membrane proteins. 3. Interior protein network: peripheral or intracellular membrane proteins. 4. Cell-surface markers: glycoproteins and glycolipids.

Amphipathic molecules:

1. Heads that are polar and hydrophilic 2. Two fatty acid tails that are hydrophobic 3. Constantly moving sideways within the membrane. Adjacent phospholipids switch positions about 10^7 times per second.

The 2 fatty acid tails in amphipathic molecules can be:

1. saturated (single bond) or unsaturated (double bond) 2. varies in length depending on needs of the cell 3. varies in temperature in which the membrane solidifies.

Integral Proteins:

1. Penetrate the hydrophobic interior of the lipid bilayer. 2. Can span the entire membrane or only partway.

Transmembrane proteins:

1. A type of integral protein 2. Spans the entire scope of membrane 3. portion which spans the membrane must be hydrophobic, the portion that extends past is hydrophilic.

Transport proteins:

1. Type of transmembrane protein 2. Specific for the substance it translocates

Channel Proteins:

1. Type of Transport protein 2. have a hydrophilic center that allows things to pass through.

Aquaporins:

1. Type of Channel protein 2. facilitate the movement of water into or out of a cell

Carrier Proteins:

1. Type of Transport protein 2. Hold onto their passengers and change shape in a way that shuttles them across the membrane

Peripheral Proteins:

1. not embedded in the lipid layer, instead they are loosely bound.

Proteins:

1. There are thousands of proteins on the membrane 2. Proteins on the membrane side can be held in place via the cytoskeleton 3. Proteins on the outside of the cell may attach to the ECM 4. The protein content of the outside of the cell will differ between cells and will differ in time on the cell. 5. The membrane proteins have many different jobs 6. some proteins move/drift in the membrane

Jobs of membrane proteins:

1. Transport: transport items in and out of the cell 2. Enzymatic activity: perform enzymatic actions within the cell 3. Cell surface receptors: receive chemical signal messages 4. cell-cell recognition: glycoproteins serve as identification tags to be recognized 5. cell-cell adhesion/intercellular joining: hook together to keep cells bound together, ex: desmosomes 6. attachment to the cytoskeleton and the ECM 7. Affect membrane structure

Cholesterol:

1. small, but strong lipid 2. wedged between phospholipid molecules 3. has different effects on membrane fluidity at different temperatures. high=less fluid, low=more fluid.

Transport across membranes:

1. major barrier to crossing the biological membrane is the hydrophobic interior. a. nonpolar molecules move until concentration is equal b. limited permeability to small, polar molecules c. VERY limited permeability to larger polar molecules and ions.

What is concentration gradient?

When there are more molecules of something in a place than in another place

What is Passive transport?

Movement of molecules through the membrane in which 1. no energy is required 2. molecules move in response to the concentration gradient

What is diffusion?

net movement of molecules from a region of high concentration to a region of low concentration.

What is a solute?

a substance dissolved in another substance

What is a solvent?

the substance into which the solutes are dissolved

What is osmosis?

when water diffuses across a membrane toward a higher solute concentration Water is the solvent and the dissolved substances are the solute.

What is a Hypertonic solution?

there is a higher concentration of solutes outside of the cell than inside the cell. There is a smaller concentration of water molecules outside than inside the cell. The cell will shrink. EX: salt water

What is a hypotonic solution?

There is a lower concentration of solutes outside of the cell than inside the cell. There is a higher concentration of water outside of the cell than inside the cell. The cell will explode. EX: pure water

What is an isotonic solution?

The concentration of solutes is the same inside and outside of the cell. EX: IV fluids

Maintaining Osmotic balance:

1. Some cells use extrusion, in which water is ejected through contractile vacuoles 2. Isosmotic regulation involves keeping cells isotonic with their environment a. Marine organisms adjust internal concentration to match sea water b. Terrestrial animals circulate isotonic fluid 3. Plants use turgor pressure to push the cell membrane against the cell wall and keep the cell rigid

What is Facilitated Diffusion?

When items move down their concentration gradient. However, because of their size, there must be a method to move the items through the tiny pores in the membrane. 1. No energy is required

What is Active Transport?

When items move up their concentration gradient 1. Energy is required 2. Transport proteins are required, highly selective carrier proteins

What is a uniporter carrier protein?

move one molecule at a time

What is a symporter carrier protein?

move two molecules in the same direction

What is an antiporter carrier protein?

move two molecules in opposite directions

What is bulk transport?

moving really large objects into the cell 1. requires energy

What is Endocytosis?

movement of substances into the cell

What is phagocytosis?

when the cell takes in a particulate matter

What is Pinocytosis?

when the cell takes in only liquid

What is receptor-mediated endocytosis?

when specific molecules are taken in after they bind to a receptor EX: hypercholesterolemia, the LDL receptors lack tails

What is exocytosis?

the movement of substances out of the cell 1. discharge of materials 2. used in plants to export cell wall material 3. used in animals to secrete hormones, neurotransmitters, and digestive enzymes.