2 lecture 4 Flashcards
what is a common feature of all cells
membranes are a common feature of all cells
what do membranes do
membranes serve as selective barriers– a barrier between the cell and the environment
what is the barrier for
a barrier between the cytoplasm and compartments inside cells
what properties do phospholipids have
phospholipids have polar and hydrophobic properties
remember that: phosphate head is polar, the tails are in the middle and not charged
does diffusion require ATP?
no
how does diffusion work
all molecules contain energy that makes them vibrate and bounce into each other
at the start, the molecules are packed into a small volume (high concentration)
at the end, they fill the available space (low concentration)
how do size and charge influence diffusion
charges molecules can get through the first layer but when it gets into the hydrophobic core it will stop, not be able to move anymore
as a consequence the size and charge have a huge effect on weather it can diffuse or not
ow do O2 and CO2 molecules pass through the plasma membrane?
passive transport
what is passive transport
diffusion from high to low concentration no energy input (ATP) is required
what is Osmosis
H2O across a membrane
is energy required for osmosis
no
how does osmosis work
the water molecules move from high to low concentration. more water = less salt
in the case of plants, when water moves out the cell wall maintains shape/size but the cell lacks turgor
what is facilitated diffusion
moving hydrophilic molecules across a membrane
how does facilitated diffusion work
proteins act as channels, allowing hydrophilic molecules to move through the hydrophobic core of the plasma membrane
how is ATP different than diffusion
the is different from diffusion… we are moving onto transport… the moment that you of against the gradient, you need energy/ATP in order to do it which is deferent than diffusion
what is the use of ATP
transport of a solute across a membrane against a concentration gradient
active transport is needed for what
active transport is needed to control the concentration of charged molecules and atoms (K+, Na+) this is very important for neurons
does active transport move big tings across a membrane
active transport also moves big things (too large for channels) across the plasma membrane
what is exocytosis
out of the cell (to the environment): exocytosis
what is endocytosis
into the cell (from the environment): endocytosis
when you take vitamin C supplements do you think the concentration is higher outside or inside of your cells?
outside— you just took a supplement so it is on the outside!
will vitamin C diffuse across a membrane like CO2 or O2? Hint: vitamin c is also called ascorbic acid
answer: very unlikely
