membranes Flashcards
(29 cards)
which part of a phospholipid is hydrophobic and which is hydrophilic
hydrophobic tails (fatty acids)
hydrophylic heads (phosphate and glycerol)
what model was put forward to show the cell membrane
fluid mosaic model
what is the role of cholesterol
in warm conditions - holds lipids together so it doesn’t break down
in cold conditions - forces tails apart to maintain fluidity
what is the role of an intrinsic protein
to let large polar molecules through
3 types of intrinsic protein and their roles
- gated protein (opens and closes in different conditions)
- channel protein (hydrophylic - always open)
- carrier protein ( for active processes that require energy - active transport)
what is passive movement + 3 examples
doesn’t require energy
- simple diffusion
- facilitated diffusion
- osmosis
what is active movement + 2 examples
movement that requires energy
- active transport
- bulk transport
what does simple diffusion transport
- small non-polar molecules
- steriod hormones
- lipid soluble vitamins (A&D)
- small polar molecules e.g. water
factors affecting diffusion
- surface area
- pressure
- concentration
- temperature
what does facilitated diffusion transport
large polar molecules (e.g. glucose)
on a graph of rate of transport against solute, describe facilitated and simple diffusion patterns
- facilitated would increased but eventually level off due to there being a set number of proteins
- simple - increase until equilibrium is reached
what is bulk transport
the movement of large molecules of large quantities that you dont want interacting with the cell their made in e.g. viruses, lactic acid
what are intrinsic proteins and how do they stay in place
trans membrane proteins that are embedded through both layers of a membrane. They have amino acids with hydrophobic R groups on their external surfaces - which interact with the hydrophobic core of the membrane to keep them in place
role of carrier proteins
has an important role in both passive transport and active transport. - this involves the shape of the protein forming
what is the role of channel proteins
to provide a hydrophilic channel that allows passive movement of polar molecules and ions
role of glycoproteins
- cell adhesion
- receptors for chemical signals
- cell recognition (recognising another cell as foreign or familiar)
what molecules require bulk transport
large molecules such as enzymes, hormones and whole cells (e.g bacteria) as they’re too large to move through channel or carrier proteins - so are moved into and out of the cell by bulk transport
what is the tonoplast and the protoplast
tonoplast = membrane around vacuole
protoplast = cell membrane and contents
what happens when a cell becomes plasmolysed
when the protoplast shrinks away from the cell wall - because water leaves the cell as when there is a lower water potential outside so water moves out the cell via osmosis
flaccid and turgid meaning
turgid - when cell in dilute solution so water moves into the cell
flaccid - when the cell in concentrated solution so water moves out the cell
what is hypertonic solution
more solute concentration
lower water potential
what is a hypotonic solution
higher water potential outside cell,
lower solute concentration
what is isotonic
no net movement
what is a crenated and heamolysed red blood cell
crenated - water moves out so cell shrinks
heamolysed - water moves in
