osmosis, passive, and active transport

Turgid

plant cells swell in a hypotonic solution

isotonic

when a cell is put into the solution, the water levels inside and outside the cell are the same

Flaccid

a plant cell at homeostasis in a isotonic solution

Fluid Mosaic Model

membrane is held together by weak hydrophobic interactions and can therefore move and shift

Glycoprotein

carbohydrates bonded to proteins

Hypertonic

cells lose water, shrivel

solution has a higher solute concentration

Hypotonic

cells gain water, swell

solution has a higher water concentration

Cholesterol

helps maintain fluidity at high and low temperatures

high- reduces movement

low- reduces tight packing of phospholipids

Lysis

animal cell swelling and exploding after being put in a hypotonic solution

Plasmolysis

plant cells shriveled after being put in a hypertonic solution

Glycolipid

carbohydrates bonded to lipids

osmoregulation

cells must be able to regulate their solute concentrations and maintain water balance

Tonicity

the ability of an extracellular solution to cause a cell to gain or loose water

Water potential

a physical property that predicts the direction water will flow

Mosaic

comprised of many macromolecules

Integral proteins

proteins that are embedded into the lipid layer

Peripheral proteins

proteins that are not embedded into the lipid bilayer

- loosely bonded to the surface

Membrane carbohydrates

important for cell-to-cell recognition

Pumps

maintain membrane potential

- sodium potassium pump (3Na out, 2K in)

Membrane potential

unequal concentrations of ions across the membrane results in an electrical charge (electrochemical gradient)

Proton pump

integral protein membrane that builds up a proton gradient across the membrane

- pumps H+ put of the cell

Cotransport

the coupling of a favorable movement of one substance with an unfavorable movement of another substance

- uses the energy stored in electrochemical gradients (generated by pumps) to move substances against their concentration gradient

- favorable movement: downhill diffusion

- unfavorable movement: uphill transport

Cotransport is used for

plants use it for sugars and amino acids

- sucrose and H+

- sucrose can travel into a plant cell against its concentration gradient ONLY if it is coupled with H+ that is diffusing down its electrochemical gradient

Exocytosis

the secretion of molecules via vesicles that fuse to the plasma membrane

- vesicles can fuse to the membrane by forming a bilayer

- once fused the contents of the vesicle are released to the extracellular fluid

- ex: nerve cells releasing neurotransmitters

Endocytosis

the uptake of molecules from vesicles fused from the plasma membrane

- phagocytosis

- pinocytosis

- receptor mediated

Phagocytosis

when a cell engulfs particles to be later digested by lysosomes

- cell surrounds particles into a food vacuole

- food vacuole fuses with lysosomes to be digested

Pinocytosis

nonspecific uptake of extracellular fluid containing dissolved molecules

- cell takes in dissolved molecules in a protein coated vesicle

- protein coat helps to mediate the transport of molecules

Receptor mediated endocytosis

specific uptake of molecules via solute binding to receptors on the plasma membrane

- allows cell to take up large quantities of a specific substance

- when solutes bind to receptors they cluster in a coated vesicle to be taken into the cell

Easy passage through membrane

small, nonpolar, hydrophobic molecules

- ex: hydrocarbons, CO2, O2, N2

Difficult passage through membrane

hydrophilic, polar molecules, large molecules, and ions

- ex: sugars, water

Passive transport

transport of a molecule that does not require energy, molecule is moving WITH electrochemical gradient

- ex: diffusion, osmosis, facilitated diffusion

Diffusion

spontaneous process resulting from the constant motion of molecules

- substances go from high to low concentrations

- move down concentration gradient

- different rates of diffusion for different molecules

Osmosis

the diffusion of water down its concentration gradient across a selectively permeable membrane

- can be thought of as diffusion of water from areas of low solute to areas of high solute

Facilitated diffusion

diffusion of molecules through the membrane via transport proteins

- increases rate of diffusion for small ions, water, and carbs

- can either go through a channel or carrier protein

Channel proteins

provides a channel for molecules and ions to pass

- hydrophilic

- many gated channels, only allow passage when there is a stimulus

Aquaporins

specific channel protein for water

Carrier proteins

undergo conformational changes for substances to pass