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Biochemistry > Lipids and Membranes > Flashcards

Lipids and Membranes Flashcards

1
Q

What is a characteristic of lipids?

A

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

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2
Q

What are the major biological roles of lipids?

A
  1. 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
  2. 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
  3. 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
  4. Protective coating to prevent infection or excessive loss of H20 eg. waxes- sebum prevents bacteria from enetring
  5. Precursors of other substances- estrogen via progesterone
  6. Some vitamins and hormones
    * get synthesized on demand
    * hormones= cortesol and aldosterone
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3
Q

Why would you want to synthesize fat soluble vitamins on demand?

A

It can go right thru the membrane because they are non polar and hormone cant … in cell and still get the effect right away

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4
Q

Do hydrophobic hormones have an easy time transporting in blood?

A

No because blood is mostly polar (hydrophilic) so they require chaperones

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5
Q

Fatty acids

A

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

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6
Q

What are some generalizations about fatty acids

A
  1. 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
  2. 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
  3. 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
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7
Q

Name some common saturated Fatty acids

A

C2:0- acetic

C10:0 capric

C12:0 lauric

C:16: palmitic

C18:0 stearic

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8
Q

Name some common unsaturated fatty acids

A

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

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9
Q

What are some properties of fatty acids?

A
  1. pka of 4.5-5
  2. Melting point- increase with increasing chain length and decreases as number of double bonds increase
  3. 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
  4. Amphipathic
  5. Structure; formation of micelle- tail inside promoting hydrophobic interaction head is (-) polar interactio with aq
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10
Q

What are fatty acids components of?

A
  1. Membrane lipids- polar

2. Storage lipids- neutral

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11
Q

Describe storage lipids

A

neutral

the simplest lipids made out of fatty acids are triglyceride or triglycerides

-esters of glycerol with fatty acids

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12
Q

What are properties and functions of triglycerides?

A
  1. Melting point- same as fatty acids
  2. most abundant family of lipids- fats and oils
    - fats are less unsaturated oils are more
  3. 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
  4. Insulation
  5. Buoyancy
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13
Q

what is saponification

A
  • 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

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14
Q

What is the first class of membrane lipids?

A
  1. Gylcerophospholipids

- derivatives of phosphatidic acid

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15
Q

ethanolamine

A

CH2-CH2NH3+

ZWITTERIONIC

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16
Q

Choline-lecithin

A

CH2-CH2-N+(CH3)3

ZWITERIONIC

17
Q

serine

A

CH2-CH-NH3+
/
COO-

-1 CHARGE

18
Q

Phospholipids

A

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

19
Q
A

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

20
Q

lysophospholipids

A

is a phospholipid from which one of the fatty acyl chains has been removed

21
Q

What happens when a lysophospholipid is put inside of water?

A

it will form a micelle because of diameter

22
Q

What is the second class of membrane lipids

A
  1. 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
23
Q

Ceramide

A

when a fatty acid is attached to a sphingosine via an amide linkage

24
Q

What are the 3 subclasses of sphingolipids?

A
  1. Sphingomyelins
  2. Glycosphingolipids
  3. Gangliosides
25
Q

Sphingomyelins

A
  • 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

-

26
Q
A

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

27
Q

Glycosphingolipids

A

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
28
Q

Why are glycosphingolipids important?

A

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

29
Q

gangliosides

A

the most complex sphingolipids and are negatively charged

have oligosaccharides as their polar head groups containing one or more sialic acid at the termini

30
Q

sialic acid

A

cellular receptor used by influenza to absorb and penetrate cells of the respiratory tract

31
Q

Describe transport across the membrane

A
  • 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

32
Q

What is a transporter analogous to?

A

An enzyme it acts as a catalyst

allows the molecule to move faster with greater ease

33
Q

uniporter

A

transports one solute

34
Q

cotransporter

A

transports 2 solutes

35
Q

antiporter

A

solutes go in different directions

36
Q

symport

A

solutes go in same direction

37
Q

describe facilitated diffusion/passive transport

A

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

38
Q

Describe glucose permease

A

glut1

is a uniporter system
12 alpha helixes form a pore that transports glucose 50000 times faster than simple diffusion thru membrane

Biochemistry (4 decks)

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