2.2.7 lipids 2: phospholipids & cholesterol Flashcards
phospholipid structure
- same as triglycerides
- except, 1 of fatty acids is replaced by phosphate group
how does an ester bond form between the phosphate group & the glycerol
condensation reaction between
- an OH group on a phosphoric acid molecule (H3PO4)
&
- 1 of 3 -OH groups on glycerol
what charge is the phosphate group when in water
negative charge - making it polar
are the fatty acid tails polar
no
is the phosphate head hydrophilic or hydrophobic
hydrophilic
is the fatty acid tail hydrophilic or hydrophobic
hydrophobic
what is the phosphate molecule
amphipathic
amphipathic
(molecule esp. protein) has hydrophilic & hydrophobic parts
properties in water of phospholipids that are amphipathic
- may form layer on surface of water –> heads in water & tails sticking out
- may form micelles = tiny balls w/ tails ticked inside & heads pointing outwards
why are amphipathic phospholipids excellent at forming membranes (around cells/organelles)
- inside/outside membrane = aqueous solution
- phospholipids form bilayer –> 2 rows
- tails point inwards & heads point outwards
what are the individual phospholipids able to do within the bilayer to provide stability
- free to move
- will not move into any position where hydrophobic tails exposed to water = stability in membrane
property of the phospholipid bilayer as a membrane to allow it to function properly
- selectively permeable
^^ only possible for small/non-polar molecules to move through tails in bilayer eg. oxygen/carbon dioxide - allows membrane to control what goes in/out of cell & allows it to function properly
what type of molecule is cholesterol
steroid alcohol
what’s a steroid alcohol
type of lipid which isn’t made from glycerol/fatty acids
structure of cholesterol
consists of 4 carbon-based rings/isoprene units
characteristics of cholesterol
- small & hydrophobic molecule
- can sit in middle of hydrophobic part of bilayer
how does cholesterol support to phospholipid bilayer/the membrane
regulates fluidity –> prevents it becoming too fluid/stiff
cholesterol production (plants/animals) - how does it differ?
animals = mainly made in liver
plants = have cholesterol derivative in membranes called stigmasterol
how is stigmasterol different from cholesterol
has double bond between C 22 & C 23
which steroid hormones are made from cholesterol
- testosterone
- oestrogen
- vitamin D
(as they’re made from cholesterol) what does it allow the steroid hormones to do regarding the membrane
(as small & hydrophobic) they’re able to pass through the hydrophobic part of the cell membrane/any membranes in cell
when can some steroid hormones be converted into animal hormones
on ingestion & absorption
