Lipids and Membranes Flashcards
What is a characteristic of lipids?
they are insoluble in water and soluble in non- polar solvents
*hydrophobic but can in certain parts engage with polar bc they might have a OH group or fatty acids
What are the major biological roles of lipids?
- Components of membranes
* allows for selective permeability because of their hydrophobic nature they can control what gets in and out of the cell
* most of the waste is polar so it allows for cell to be highly regulated environment - Storage form of carbon and energy
*fats store 2x more energy than sugars- this is more efficient and thats why store additional energy as lipids
*highly reduced lots of H= electron
high electrons mean high NADH and FADH2 = high ATP yield in ETC - Insulation barriers to avoid thermal electrical and physical shock
* trap heat= we are endothermic so we have to regulate our body temperature
if we didn’t use fats for insulating we couldn’t maintain energy for other things because we would have to use energy for muscle contractions to gain heat to get body temperature back
*electrical insulation of neuron- myelin is hydrophobic which allows for movement of ions only when you want rapid transmission
*destroyed in ppl who have multiple sclerosis - Protective coating to prevent infection or excessive loss of H20 eg. waxes- sebum prevents bacteria from enetring
- Precursors of other substances- estrogen via progesterone
- Some vitamins and hormones
* get synthesized on demand
* hormones= cortesol and aldosterone
Why would you want to synthesize fat soluble vitamins on demand?
It can go right thru the membrane because they are non polar and hormone cant … in cell and still get the effect right away
Do hydrophobic hormones have an easy time transporting in blood?
No because blood is mostly polar (hydrophilic) so they require chaperones
Fatty acids
are amphipathic long chain aliphatic(not aromatic, linear) carboxylic acid
-long chain saturated no double bonds/kinks) are least soluble in water
released from fat upon hydrolysis
- not often found in cells in free form but instead are combined in complex lipids
What are some generalizations about fatty acids
- Most are monocarboxylic acids with linear(unbranched) hydrocarbon chains and have an even number of C atoms C12 to C24
shorter longer odd numbered or cyclic do occur but are less frequent - Unsaturated fatty acids (one or more C-C double bonds) are also common
most common are C18 and C20
when 2 or more double bonds exist they are separated by single methylene bridge - All naturally occuring fatty acids the double bonds are in cis configuration
trans fatty acids produced by hydrogenation process in food have been linked to heart disease
Name some common saturated Fatty acids
C2:0- acetic
C10:0 capric
C12:0 lauric
C:16: palmitic
C18:0 stearic
Name some common unsaturated fatty acids
delta 9 C16:1- palmitoleic
delta 9 C18:1-oleic
delta 9,12 C18:2- linoleic
delta 6,9,12 C18:3- y-lionelic
delta 9,12,15 C18:3- a-linoleic
What are some properties of fatty acids?
- pka of 4.5-5
- Melting point- increase with increasing chain length and decreases as number of double bonds increase
- solubility
- fatty acids are soluble up to C6 and then only in non polar solvents
- up to C6 they wont cause decrease in entropy
C6 tail is so hydrophobic it makes more sense to put it in non polar solvent - Amphipathic
- Structure; formation of micelle- tail inside promoting hydrophobic interaction head is (-) polar interactio with aq
What are fatty acids components of?
- Membrane lipids- polar
2. Storage lipids- neutral
Describe storage lipids
neutral
the simplest lipids made out of fatty acids are triglyceride or triglycerides
-esters of glycerol with fatty acids
What are properties and functions of triglycerides?
- Melting point- same as fatty acids
- most abundant family of lipids- fats and oils
- fats are less unsaturated oils are more - energy storage, fat cells (adipocytes), oil seeds(canola, sunflower)
Since the C is more reduced than in carbs fats have 2x more energy per unit mass
*fats are heavily reduced lots of electrons bound on carbon backbone - Insulation
- Buoyancy
what is saponification
- soap making
fatty acid products form micelles in H20 which can carry oil in their interiors and still be soluble in H20 this is how soap works to remove grease dirts
intestinal lipases catalyze enzymatic hydrolysis of TAGs
What is the first class of membrane lipids?
- Gylcerophospholipids
- derivatives of phosphatidic acid
ethanolamine
CH2-CH2NH3+
ZWITTERIONIC
Choline-lecithin
CH2-CH2-N+(CH3)3
ZWITERIONIC
serine
CH2-CH-NH3+
/
COO-
-1 CHARGE
Phospholipids
are amphipathic so they form bilayers due to the hydrophobic effect and this allows them to assemble membranes
results in the molecule having a polar head and non polar tail
*NAtural behaviour is bilayer not micelle
a) micelle- individual units are wedge shaped cross section of head greater than that of chain)
* diameter of head is wider than diameter of single tail
* fatty acids detergents lysophospholipids
b)bilayer- diameter of head is comparable to diameter of tail
c)vesicle liposome
- if enough they naturally close up
used for delivery of Mrna vaccine
lysophospholipids
is a phospholipid from which one of the fatty acyl chains has been removed
What happens when a lysophospholipid is put inside of water?
it will form a micelle because of diameter
What is the second class of membrane lipids
- Sphingolipids
- important in membranes of plants and animals
- particularly in brain and peripheral nervous system
- not glycerol derivatives but derivatives of sphingosine (replaces glycerol) with one fatty acid tail
Ceramide
when a fatty acid is attached to a sphingosine via an amide linkage
What are the 3 subclasses of sphingolipids?
- Sphingomyelins
- Glycosphingolipids
- Gangliosides
Sphingomyelins
- the head group is phosphocholine
- no net charge on head group
- have same properties as phosphatidylocholine
- found in plasma membrane of animals especially in myelin
- provides insulation hydrophobic exterior, which protects against ion movement so you can control where ions can move so you can quickly propagate a electrical signal to be able to send messages to nervous system- saltatory propogation signals are jumping from where myelin is not present
-
people who have mS the sphingomyelins have been destroyed because of autoimmune activity dont have insulation have signal interference and inefficiency when you try to send signals in brain
Glycosphingolipids
neutral- no charge
cerebrosides- head group is one sugar unit linked to ceramide
globosides- head group is more than one sugar no charge
- found on the outer face of the plasma membrane and important in cell to cell recognition
-human blood group determinants
O,A,B and blood group antigens are glycosphingolipids with different complex carbs head groups
Why are glycosphingolipids important?
ex if you give inappropriate blood to a person the carbs wont match what they are used to and immune response activates destroying cells so you have to make sure the carbs match
gangliosides
the most complex sphingolipids and are negatively charged
have oligosaccharides as their polar head groups containing one or more sialic acid at the termini
sialic acid
cellular receptor used by influenza to absorb and penetrate cells of the respiratory tract
Describe transport across the membrane
- only a few non polar molecules can dissolved in the lipid bilayer and cross the membrane unassisted
ex- o2 n2 Co2 CH4 some drugs - they will need to shed their water shell and pass directly thru need to be small enough so they aren’t disruptive
polar molecules shed their water shel and them use transporter
MOST use protein mediated process
What is a transporter analogous to?
An enzyme it acts as a catalyst
allows the molecule to move faster with greater ease
uniporter
transports one solute
cotransporter
transports 2 solutes
antiporter
solutes go in different directions
symport
solutes go in same direction
describe facilitated diffusion/passive transport
uses transporter or permease protein- lower activation energy of transport
going down the concentration gradient from high concentration to low concentration
*cannot accumulate the transported molecules beyond equ’ position
once you have an = concentration on both sides transport stops
- doesn’t require energy but releases it
ex- glucose permease
chloride bicarbonate exchanger
Describe glucose permease
glut1
is a uniporter system
12 alpha helixes form a pore that transports glucose 50000 times faster than simple diffusion thru membrane
