AP BIO chapter 7

plasma membrane

boundry that separates the living cell from its surroundings

selective permiablility

allows some substances to pass easier than others

trait of the plasma membrane

phospholipids

most abundant lipids in the PM

are amphipathic molecule (hydrophilic head and phobic tail)

phospholipid bilayer 

acts as a stable boundary between 2 watery compartments 

fluid mosaic model

membrane is a fluid structure with a mosic of different proteins embedded in it

proteins are not randomly distributed

as temp cools. membranes

switch from fluid to solid

the temp that a membrane solidifies depends

on its type of lipids 

membranes with more unsaturated fatty acids

more fluid than ones with more saturated fatty acids

to work right membranes must

be fluid

cholesteral in membranes

at warm temps restrains movement of phosphlipids and at cool temps it maintains fluiity

ti adapt to different environmental conditions organisms

change their lipid composition

proteins determine

most of the membrane specific functions

hydrophobic regions of a integral protein consist of

struches of nonolar amino acid coiled into alpha helices

6 major functions of membrane proteins

1. transport

2. enzymatic activity

3. signal transduction (cell phone)

4. cell cell recognition (cell tells the cell what it is)

5. intercellular joining (joining space between cells (glue)

6. attachment to the cytoskeleton and ECM

cells recognize each other by

by binding to molecules on the surface of the extracellular surface

inside and out faces of the membrane called

cytoplasm and extracellular

a cell must

exhange materials with its surroundings (controlled by the PM)

hydrophobic tails of phospholipids form a

nonpolar interior that can easily dissolve as pass through rapidly (hydrocarbons and co2)

dont cross the membrane easily

hydrophilic molecules (na+ and ca+)

transport proteins 

allow passage of hydrophilic substances across membrane 

are specific for the substance it moves 

channel proteins

have hydrophilic chalnnel used as a tunnel

aquporins

facilitate the passage of water

carrier proteins 

bind to molecules and change shape to shuttle them across the membrane

diffusion

the tendency for molecules to spread out evenly into abalible space

at dynamic equilibrium

as many molecules cross the membrane in one direction as in the other

substances diffuse

down their concentration gradient

diffusion of a substance across a biological membrane is

passive transport because it dosnt’t use energy to make it hapepn

osmosis

diffusion of water across a selective permiable membrane

water diffuses across a membrane from the region of

lower solute concentration to higher solute concentration until it is = on both sides

tonicity

maintain their water balance which depends on the solute concentration, and can either cause cells to gain or lose water

isotonic solution

solute concentration is = inside and outside the cell

hypertonic solution

solute concentration is higher outside the cell

water moves out of the cell causing it to shrink

hypotonic solution

solute concentration is lower outside the cell

water moves in the cell cause it to swell

osmoregulation

controlling water and solute consentration to maintain homeostasis

cell wall help

maintain water balance

plant cells in hypotonic solution

swells until wall oposes uptake and turns turgid or firm

in hypertonic environment plant cells

lose water membrane pulls away cause the plant to wilt

facilitated diffusion transport protens

speed the passive movement of molecules across the plasma membrane

transport proteins include

channel proteins: provide corridors that allow a specific molecule or ion to cross the membrane

ion channels: facilitate the diffusion of ions gated channels open or close in response to a stimulus

carrier proteins: undergo a subtle change in shape that translocates the solute binding site across the membrane

membrane potential

the voltage difference across a membrane measured in mV

ions have a 

electrochemical gradient because they have a charge

electronegative pumps

pumps that are going to move ions (go against concentration gradient using ATP)

sodium potassium pump

protein changes shape (conformation change)

3 na+ gets in

phosphate group from ATP attaches to the pump

na+ goes outside the cell

2 k+ go in and phosphate groups leaves so the shape changes back

k+ goes indise  the cell

proton pump (plants and bacteria)

must use ATP

pumping H+ out so the interior gets more negative

cotransport

• using proton pump with the h+ outside

• open door to go down the gradient

• meanwhile sucrose (goes up the gradient) piggy back off and go in the cell

bulk transport

bring in or let out big things (like large molecules or proteins)

extocytosis

• type of release of large materials out of the cell

• vesicles leaving the golgi, fuse to the cell membrane and release the contents to the outside (insulin, nerve cells for nurotransmitters, plant cells)

• secratory cell (secreation)

endocytosis

• bring things in the cell

1. phagocytosis - bing in solid (eating)

2. pinocytosis - bring in liquid (drinking)

3. Receptor-mediated endocytosis (helped by receptors)