Anatomy & Physiology Lecture Notes - Ch. 3 cells - part 2

1. Name the three basic parts of a cell and describe the functions of each.

2. Why do phospholipids organize into a bilayer – tail-to-tail – in a watery environment?

Hypertonic, isotonic, or hypotonic?1. What type of fluid might be infused into

the bloodstream of a patient who needs fluid drawn out from swollen tissues?

2. What type of fluid might be used (carefully) to rehydrate the tissues of extremely dehydrated patients?

3. In a U-tube separated by a selectively permeable membrane, there is .2 M glucose in Side A, and .4 M glucose in Side B. Side A is ____ compared to Side B, and Side B is ____ compared to Side A.

4. If the membrane in #3 is only permeable to water, what will happen?

Part 2: Membrane Transport

Interstitial fluidInterstitial fluid: Fluid outside cells Rich, nutritious “soup” – amino acids,

sugars, fatty acids, vitamins, hormones, salts, wastes

Selective PermeabilitySelective Permeability: Plasma membrane only allows some

substances to enter cell Nutrients in, wastes out By passivepassive or activeactive transport

No energy (ATP) needed Molecules move down concentration down concentration

gradientgradient from HIGH LOW concentration

Types: diffusion, filtration

Nonpolar & lipid-soluble Nonpolar & lipid-soluble substancessubstances diffuse directly through lipid bilayer

Eg. O2, CO2, fat-soluble vitamins

Transport proteins Transport proteins (carrier or channel proteins) assist molecules across membrane

Eg. glucose, amino acids, H2O, ions

Water-filled channels Eg. ions

Binds to molecule, changes shape, ferries it across membrane

Eg. glucose transporter

Diffusion of H2O Aquaporins: Aquaporins: channel proteins for H2O

passage

Ability of solution to change shape or tone of cells by changing water volume

IsotonicIsotonic = equal concentration solutes HypertonicHypertonic = higher conc. of solutes HypotonicHypotonic = lower conc. of solutes

Energy (ATP) is needed!! Move molecules against concentration against concentration

gradientgradient from LOW HIGH concentration

Types: Primary and Secondary

Directly uses ATPATP to drive transport

Eg. Ca2+ pump, H+ pump, Na+-K+ pump

Sodium-Potassium PumpSodium-Potassium Pump

Move more than 1 substance at a time SymportSymport: 2 substances moved in same direction AntiportAntiport: 2 substances cross in opposite

directions Eg. cotransport of sugars, animo acids, ions

Fluid & large particles transported across membranes in vesiclesvesicles (sacs)

ExocytosisExocytosis: “out of cell” – eject substances

EndocytosisEndocytosis: “within the cell”- ingest substances

PhagocytosisPhagocytosis: (cell eating) – engulf large or solid materialeg. WBC engulf

bacteria

PinocytosisPinocytosis: (cell drinking) – fluid w/dissolved moleculesEg. intestinal

cells

Receptor-Receptor-mediated mediated endocytosisendocytosis: concentrate specific substances (ligandsligands) that bind to receptor receptor proteinsproteinsEg. insulin, iron,

cholesterol