bio exam 2 ch. 5

• Common: to all cells
• Separates: cell contents from environment (holds things in)
• Phospholipid bilayer: barrier of hydrophobic and hydrophilic things

endo and exoytosis

• •Lipid component (phospholipid bi-layer)
• •Protein molecules (within the bi-layer)–Integral proteins: proteins partially or wholly embedded in the membrane itself
• –Peripheral proteins: do not go all the way through the bi-layer; is only on the outer layers
• •Cholesterol–Affects the fluidity of the membrane; lies underneath the membrane giving it support and structure

• Channel Proteins: allow passage of particular molecules or ions via a channel (line tunnels in the membrane) passive; no energy required
• Carrier Proteins: actively carries a molecule thru the membrane energy required; or changes the molecule’s shape; passive, no energy required
• Cell Recognition Proteins: mostly glycoproteins (have a carbohydrate chain attached to it) identification friend or foe Ex. Histocompatibility complex

• Receptor Proteins: lock/ key mechanism. only a molecule with the right physical shape can fit in them; like a lock and key
• Enzymatic Proteins: catalyze specific reactions (facilitate reactions) in the picture, the protein makes a reaction where the brown thing turns to the purple triangle
• Junction Proteins: holds cells together; form junctions between cells  (between phospholipid bi-layers of those cells; see picture on 14. phospholipid bi-layers shown are of two different cells)

• 1. binding of the signaling molecule
• 2. transduction of the signal
• 3. response of the cell depending on what type of protein is targeted

selectively permeable; small non-charged molecules move freely across the membrane flowing down a concentration gradient

the way these molecules move across the plasma membrane

• movement of molecules from a higher to lower concentration; down their concentration gradient; until equilibrium is achieved (passive)
• Diffusion works as a transport mechanism as long as the substance to be transported is small, and the concentration gradient is favorable (high to low concentration).

when molecules move against concentration gradient. requires energy

bulk transport: a way that large particles enter or exit a cell

exocytosis: moving a particle outside of the cell

endocytosis: move a particle into the cell

• phagocytosis- large solid material gets engulfed and surrounded by vesicles
• pinocytosis- liquid or very small particles
• receptor-mediated endocytosis: pinocytosis using receptor proteins to recognize compatible molecules and bring them into the cell

• diffusion and facilitated transport: passive
• active and bulk transport: active

a solute and a solvent

liquid

dissolved solid

movement of water across a semi-permeable membrane from high to low concentration

pressure that develops due to osmosis

• osmosis is the movement of water across a semi-permeable membrane
• diffusion is movement of molecules down a concentration gradient

The strength of solution is defined as the amount of solute in grams present in one liter

• no net gain or loss of water by the cell
• solute and water concentration equal on both sides of the membrane

• Hypo- less than (low salt/no salt)
• solution with a lower concentration of solute outside the cell than inside the cell
• cells placed in a hypotonic solution will swell
• fish in fresh water (has to pee because cells are always swelling with water)

• hyper- more than (lots of salt)
• solution with a higher percentage of solute outside the cell than inside the cell
• cells placed in hypertonic solution will shrink
• fish in salt water (has to drink because cells are always shrinking)

when animal cells are placed in a hypertonic solution (shrink)

when plant cells are placed in hypertonic solution (shrink)

bursting of blood cells

when a plant cell swells due to a hypotonic solution

• how molecules are rapidly transported across the plasma membrane
• passive; following concentration gradient from high to low concentration

• movement against concentration gradient  from low to high concentration
• requires energy
• facilitated by carrier proteins called pumps

how the concentration gradient is maintained; two proteins that work together

the protein is moving one molecule in one direction and another molecule in a different direction

• adhesion junction
• tight junction
• gap junction

adhesive proteins connect two cells

tight junctions between cells form an impermeable barrier because their adjacent plasma membranes are joined and don't allow molecules to pass

allow communication between two cells because adjacent plasma membrane channels are joined

numerous narrow, membrane-lined channels that pass through the cell wall