Cell Transport Mechanisms

membrane, osmosis, diffusion, active transport

Structure of the Cell Membrane affects transport of materials? (5)

polar molecules are charged, phospholipids contain a hydrophilic head, hydrophobic tail, the head faces outwards and interacts with aqueous environment, the tail inwards, therefore polar molecules are repelled before they can pass through the hydrophobic tails, so they must pass through carrier proteins instead

Importance of phospholipid with cell membrane? (3)

the phosphate head is hydrophilic, the fatty acid tails are hydrophobic. the phosphate interact with the aqueous environment. otherwise lipids will not form a bilayer. this creates a hydrophobic barrier.

Temperature and permeability/fluidity of membrane (3)

higher temperature results in higher membrane fluidity as the phospholipids are able to move more (have more KE). This increases the permeability. Above a certain temperature, proteins denature, causing the membrane to become even more fluid.

Why is membrane fluidity needed?

Because membranes control permeability. And control uptake of nutrients. because membranes need to be fluid for cell division

osmosis key words

water potential. Moves down water potential.

active transport definition (3)

movement of molecules against the concentration gradient, using atp, using carrier proteins

facilitated diffusion when

charged molecules, down the concentration gradient

why is osmotic potential hard to determine?

you cannot directly measure it, can only be measured via incipient plasmolysis

3 stages of plasmolysis

incipient, evident, final

Turgor pressure definition

Turgor pressure is the force of the cell membrane against the cell wall

water potential vs osmotic potential

water: likelihood of water moving out of a solution. osmotic: the measure of water moving out

describe the structure of a phospholipid

a hydrophilic phosphate head attached to a glycerol group attached to 2 hydrophobic fatty acid tails

water potential depends on…

the number of molecules rather than the concentration

diffusion definition

mvmt of molecules from high to low conc