bio e

chapter 7

Plasma Membrane

the boundary that separates a living cell from its surroundings

fluid mosaic model

what is used to describe the structural functions of the cell membrane

unsaturated fats

health fats

liquid at room temperature

saturated fats

unhealthy fats

solid at room temperature

Phospholipids

• are amphipathic

• head (round part) is hydrophilic

• tail (fatty bottom) is hydrophobic

high permeability

gases have high permeability; they are very small uncharged molecules

• CO2 (carbon dioxide)

• N2 (nitrogen)

• O2 (oxygen)

• ethanol

moderate permeability

allows for this to pass through the artificial bilayer at a neither fast or slow rate

water (H2O) and urea (H2NCONH) have moderate permeability

low permeability

does not allow for fluids or minerals to pass through the artificial bilayer easily

polar organic molecules (sugars) have low permeability

very low permeability

does not let fluids or minerals to pass through (artificial bilayer) easily

• ions (Na+, K+, Mg2+, Ca2+, Cl+

• charged polar molecules

• macromolecules (amino acids, ATP, proteins, polysaccharides, nucleic acids; DNA and RNA)

Phospholipids

saturated hydrocarbon tails

increases the viscosity (thickness)

their shape is tightly packed, leaving minimal space between the molecules

unsaturated hydrocarbon tails

have double bonds

promotes more fluidity

plasma cell membrane

regulates and allows certain things to come in and out

is a fluid mosaic model (functionally)

it’s is selectively permeable (structurally)

amphipathic

having both hydrophobic and hydrophilic parts; having both polar and nonpolar parts;

Passive Transport

diffusion of a substance across a membrane with out energy investment

• EX: CHANNEL PROTEINS

diffusion and osmosis

both are passive transport since no energy is required by cells to make it happen

what does passive transport do

diffuses substances DOWN their concentration gradient

• solute will move from the side that has more to the side with less

isotonic solution

a solution that has the same solute concentration as the inside cell

• no water movement

hypertonic solution

a solute concentration that is higher than that inside cell

• cell loses water

hypotonic concentration

a solute concentration is less than that inside cell

• cell gains water

Transport Proteins

allows for hydrophilic substances to pass through the membrane

• some allow passive transport; some do active transport

Channel Proteins

• transports molecules and ions faster than carrier proteins

• have a hydrophilic channel that certain molecules and ions can pass through and use as a tunnel

Carrier Proteins

• requires energy to transport molecules

• binds to molecules or ions on one side of the membrane and releases it on the other side of the membrane (does not provide a tunnel for transport)

Active Transport

• moves substances AGAINST their concentration gradients and requires energy (ATP)

  • EX: CARRIER PROTEINS