ap bio 2.4-2.9 membranes, transport, and osmosis

amphipathic

polar/hydrophilic on one side and nonpolar/hydrophobic on other

functions of plasma membrane

-outlines cells borders

-determines how it interacts with env

-carries markers allowing for recognition of pathogens

properties of plasma membrane

-receive signals for effectors and growth factors

-flexible so things can fit through

-semipermeable

fluid mosaic model

phospholipids reorganize themselves like fluid

what type of phospholipids are more flexible in membrane

unsaturated fatty acids

carbs in plasma membrane (10% of mass)

-only on exterior surface

-glycolipids and glycoproteins

-used as cell markers for communication

lipids in plasma membrane (40% mass)

-phospholipids and cholesterol

role of cholesterol in membrane

buffers fluidity agaisnt temp changes

-in warm temperatures, molecules want to spread apart and cholesterol keeps them connected

-in cold temperatures molecules want to stay close and cholesterol helps separate it

amount of proteins in membrane

50% of mass

integral proteins

attach completely into membrane

r groups on membrane region are nonpolar

r groups that protrude and contact extracellular fluid are polar

peripheral proteins

either attached to integral proteins or phospholipids

what kind of molecules CANT pass through the cell membrane because of the nonpolar lipid intermembrane

large nonpolar, or polar molecules

ex glucose and amino acids

passive transport

movement down concentration gradient (high to low concentration)

no energy needed

natural

simple diffusion

small uncharged molecules can easily pass through

(nonpolar and lipid soluble)

how does steepness of the concentration gradient impact diffusion

steeper/bigger difference means diffusion will happen faster

how does mass of molecule impact diffusion

bigger molecules are slower at passing through the membrane

how does temp impact diffusion

hotter means more energy so faster

how does solvent density impact diffusion

higher density means slower diffusion

facilitated diffusion

still part of passive so no energy

uses transport protein: channel or carrier

channel proteins

aquaporin for water

ion channel for ions

gated ion channel only allows to pass sometimes

carrier proteins

changes shape to move the molecule down membrane (bound molecules)

active transport

always facilitated but uses energy

moves against concentration gradient

electrochemical gradient

combined conc gradient + electrical charge that affect ion movement

electrical gradient

difference of charge across plasma membrane in volts

cell has negative charge compared to outside

pumps

use of ATP to move substances against gradient

primary active transport

direct use of ATP to move ions across membrane and create charge difference

secondary active transport

no direct atp use

uses energy stored in electrochemical gradient

proton pumps

sends H+ ions outside to create difference in charges

can create higher acidity which is specific to certain proteins

uniporter

carrier protein for active transport

goes down one way

symporter

carrier protein for active transport

sends two things down same way

antiporter

carrier protein for active transport

sends two things down in opposite directions

sodium potassium pump

NA+ -K+ ATPase

found in all animal cells

pumps 3K+ in and 2NA+ out for each ATP

pumps high concentrations of sodium outside the cell

activated when phosphate is taken from ATP

maintains high concentration of sodium outside neurons and potassium inside neurons

endocytosis

active transport moves large particles or other cells into cell

membrane pinches off and creates new vesicle

phagocytosis

takes in large particles by endocytosis

pinocytosis

takes in extracellular fluid by endocytosis

exocytosis

expels material by vesicle fusing with plasma membrane

osmosis

diffusion of water molecules according to concentration gradient

can be simple (but takes long)

usually facilitated with aquaporin

ways that water moves

high water concentration to low water concentration

low solute concentration to high water concentration

high pressure to low pressure

tonicity

extracellular solution changes cell volume by affecting osmosis

osmolarity

total solute concentration

osmoregulation

ability of cells to regulate solute concentration and maintain cell balance

hypertonic solution

higher osmolarity

higher solute

water moves towards hypertonic side

if outside cell, cell will shrivel from water loss

plasmolysis

occurs in hypertonic solutions

vacuole shrinks and plasma membrane moves away from walls

hypotonic

lower osmolarity/lower solute

water moves AWAY from

water will move into cell and lyse

isotonic

net water movement of 0 bc moves in and out at same time

optimal condition for plant cells

hypotonic solution, cell wall prevents lyses

what happens to plants in isotonic conditions

vacuole doesnt exert enough pressure so they wilt

what happens to plants in hypertonic solutions

cells will shrivl and die due to plasmolysis

water potential

measures potential energy of water in pressure units

predicts direction of flow

how does water move based on potential

high water potential to low water potential

ion constant to know for solute potential formula

glucose=1

NaCl=2