chap 3: the plasma membrane Flashcards
what is the fluid mosaic model?
it describes the plasma membrane and how it looks.
what is it (fluid mosaic model) made of?
the fluid mosaic model, is also known as the phospholipid bilayer, is made of 2 layers of phosphate heads and 2 fatty tails.
what is the phosphate head?
the phosphate head is made of a glycerol and phosphate group. it is negatively charged, polar, and hydrophilic, meaning it loves water. This is why its facing the inside and the outside of the cell as in and out of the cell contain water, meaning it’s attracted to it.
what are fatty acid tails?
they are long chains of carbon and hydrogen. they are uncharged, hydrophobic and non polar (they don’t have a clear positive or negative end)
what increases/decreases membrane fluidity?
temperature
if its cold, they get close together, while if its hot, its too fluid and doesn’t hold it’s shape
cholesterol - it holds the phospholipids tother so they don’t seperate too far, or constricting together too much.
why don’t some substances readily diffuse across the plasma membrane? what are some examples and why?
only small, non polar, uncharged, and hydrophobic will freely diffuse through the plasma membrane. this is because other things will just bounce off of it. things such as ions, amino acids and proteins can’t pass through. these things can’t passively pass through the cell membrane because of size and polarity.
what is facilitated diffusion?
facilitated diffusion is when molecules can go through protein channels without the need for energy. This is going down/following the concentration gradient.
what is active transport?
active transport is when a molecule needs energy (ATP) to be moved across the cell membrane. this is because the molecule will be moving against the concentration gradient
what is bulk transport?
when large quantities/large molecules are move across the cell membrane named endocytosis and exocytosis.
what is endocytosis?
it is the process where the larger substance/s is taken into a cell.
1. the membrane will make a fold, concaving itself and filling the concave with the substances.
2. the membrane folds back on its self until it closes, trapping the substances in the membrane.
3. the vesicle is them pinched off the membrane, and transported.
what is exocytosis?
this is the process where larger substances are being taken out of a cell.
1. a vesicle carrying the substances wanting to be taken out is transported to the cell membrane
2. the membrane and the vesicle fuse
3. the substances are released from the vesicle to the outside of the cell.
what is osmosis?
a type of passive transport which is the movement of water in and out of a cell according to the concentration gradient. also known as tonicity
what is tonicity?
the ability of a solution to influence osmosis
what is hypertonicity?
when a cell loses a volume because of the solutes concentration outside of the cell is higher than outside of the cell. these means that the solute can’t pass through the membrane
what is hypotonic
when a cell gains volume because the solutes concentration inside of the cell is higher than inside of the cell. this means that the water will cross into the membrane to dilute it.
