BIO 141 - ch 7 - Membranes

• semi permeable, some things get through some don’t, it protects the cell because of its control. allows for the storage of energy by moving things from one side to the other - transfer of energy

• allows for molecules [enzymes, cytochromes] to be close to each other

• phospholipids - polar and non polar

membrane

• function

• importance of location

• what’s it made of

have a hydrophilic head [outside] and hydro phobic tail [inside]

they are arranged in a bilayer with the phillic heads facing out and the phobic heads on the inside

Describe the properties of phospholipids and their arrangement in cellular membranes.

they split the membrane down the middle of the phospholipid bilayer and are proteins embedded directly within the core of the membrane rather than just sitting of the surface

Explain what freeze-fracture techniques reveal about the involvement of proteins in membranes.

fluid properties have more spacing between the hydrophilic heads

they have unsaturated hydrocarbon tails -double bonds

this makes it easier for things to pass through the membrane

Describe the fluid properties of the cell membrane and explain how membrane fluidity is influenced by membrane composition.

carbohydrates are located exclusively on the extracellular side

Describe how proteins and carbohydrates are spatially arranged in cell membranes and how they contribute to membrane function.

concentration gradients - molecules want to move from high to low concentrations

• ex. more Na is outside the cell so they will go in and more K is in the cell so they will go out

transport proteins regulate what can go in and out of the cell

protein channels are specific to what ions can pass through

Describe factors that affect the selective permeability of membranes.

they are located spanning across the membrane

• integral proteins span across the membrane or peripheral proteins attach to the surface

they function as channels or carriers to help specific molecules, ions, and water cross the hydrophobic barrier

Describe the locations and functions of transport proteins.

it is the movement of particles from a high concentration to low

takes no energy

the driving force is the concentration gradient

Define diffusion. Explain what is the driving force behind diffusion.

it is regulated by the concentration gradient

have channels specific to what can pass through

it is basically diffusion with some help

no energy

Explain what regulates the rate of passive transport.

molecules naturally store energy when moved by a concentration, which is released as they flow down their gradient to perform work

Explain why a concentration gradient across a membrane represents potential energy.

hypotonic

• animal = lysed - over filled

• plant = turgid - normal

• more water less solute inside cell

isotonic

• animal = normal

• plant = flaccid - under filled

hypertonic

• animal = shriveled

• plant - plasmolyzed

• more solute less water inside cell

Distinguish between hypertonic, hypotonic, and isotonic solutions.

its the diffusion of water across a selectively permiable membrane

water moves from an area of lower solute concentration [higher water] to an area of higher solute concentration [ lower water ]

Define osmosis and predict the direction of water movement based on differences in solute concentrations.

They go across the membrane

take a certain amount of proteins across and need ATP to be phosphorylated in order to change cell shape and move contents across membrane.

Explain how transport proteins are structurally organized.

facilitated is like diffusion with some help

the ions are still moving with their concentration gradient - so its passive

the channel is specific to what can pass through

some are carrier proteins that change their shape to help the movement of a solute

[there are two types a channel type and a switch type]

Explain how transport proteins facilitate diffusion.

it requires energy because it moves substances against their concentration gradient

when ATP comes along it phosphorylates the protein - allowing it to shift

when K comes the protein dephosphorylates

• for example the Na/K pump when Na attaches to the protein ATP phosphorylates, attaching a P to the protein and giving it the energy to shift and release the Na to the other side.

• then K comes and attached to the pump, it can use the P again to drive the K into the cell then

Explain how active transport differs from diffusion

ion pumps [like the Na / K pump or proton pump] use ATP to actively transport ions across the membrane against their gradient, creating unequal distribution of charge and concentration

Explain what mechanism can generate a membrane potential or electrochemical gradient

in a proton pump energy is needed to get H from inside the cell [in tje cytoplasm] to outside the cell [extracellular]

once the H build up it can diffuse back into the cell and sucruse can use the H to move with it

it is using an exergonic motion to drive and endergonic

Describe the process of co-transport

dont

• diffusion

• facilitated diffusion

do

• active transport

• endo/exocytosis

what membrane processes need energy vs which dont

1. facilitated diffusion

2. diffusion

3. .

4. diffusion

5. aquaporins

6. facilitated diffusion

how do each of these move through proteins - what method of travel

1. carb

2. lipid

3. protein

4. gasses

5. water

6. ions