BS120: Lipids 1 Flashcards
Define lipids
lipids are heterogeneous class of naturally-occurring organic compounds that are insoluble in water but soluble in organic solvents.
What do lipids lack?
- a distinguising functional group
- a structural feature.
solubility of lipids
what is the solubility of lipids?
- relatively insoluble in polar solvents, like water
- freely soluble in nonpolar organic solvents (benzene, ether, chloroform)
- certain lipids exhibit an amphipathic character
solubility of lipids
How can certain lipids be amphipathic?
By possessing both hydrophilic and hydrophobic regions within the same molecule.
solubility of lipids
What does the amphipathic nature of lipids allow for?
It allows lipids to form essential structures, such as the cell membrane.
biological importance of lipids
What are the 8 functions of lipids?
with example of lipids that perform each function
- energy [triglycerides]
- structure [phospholipids & cholestrol]
- isolation [subcutaneous fat & the myelin sheath]
- protection [pads of fat]
- absorption [amphipathic lipids, ex. bile salts]
- transportation [lipoproteins]
- regulation [steroid hormones & prostaglandins]
- precursors [cholestrol]
How do lipids perform energy-related roles?
lipids are energy storage molecules, providing a supply of essential fatty acids.
- triglycerides store 9Kcal/g
How do lipids perform structure-related roles?
lipids are structural components of biomembranes.
- lipids like phospholipids & cholestrol regulate membrane permeability
How do lipids perform insultation-related roles?
- lipids, like those in subcutaneous fat, act as thermal insulators against loss of body heat
- lipids, like those in the myelin sheath, act as electric insulators in neurons.
How do lipids perform protection-related roles?
lipids, like pads of fat, protect internal organs by providing a “cushioning” effect.
How do lipids perform absorption-related roles?
lipids act as surfactants, detergents, & emulsifying agents. This makes them helpful in absorption of fat-soluble vitamins.
What are fat-soluble vitamins?
vitamins K, E, D, A
all these vitamins can be absorped by amphipathic lipids such as bile salts.
How do lipids perform transportation-related roles?
lipids, such as lipoproteins, transport other lipids.
How do lipids perform regulation-related roles?
lipids, like steroid hormones & prostaglandins, function as cell signaling molecules& metabolic regulators.
How can lipids act as precursors?
Lipids, namely cholestrol, are precursors of steroid hormones & vitamin D.
what is the symbol for fatty acids?
F.A.
What is the chemical formula of F.A.?
R-(CH2)n-COOH
What does the R stand for in the chemical formula of fatty acids?
R stands for hydrocarbon chain.
Define fatty acids
Aliphatic carboxylic acids.
- they are carboxylic acids with hydrocarbon chains
What are the components of F.A?
- head & tail
- head: hydrophilic, polar carboxyl
- tail: hydrophobic, nonpolar hydrocarbon chain (hydrophobic chain)
What is the solubility of fatty acids?
They are amphipathic in nature.
What do F.A.s form in water?
They form spherical clusters called micelles.
Why are micelles important?
Micelles are important for biological functions like the transport of insoluble lipids in the blood.
What are the qualities of the tail of fatty acids?
- nonpolar
- hydrocarbon chain
- always aliphatic, never aromatic
- most are even chains, few are odd
- most are linear chains, few are cyclic
- most are unbranched chains, few are branched
- can be saturated or unsaturated
What is the length of FA?
- Short-chain FA
- Medium-chain FA
- Long-chain FA
How many carbons are in a short-chain FA?
4 to 5 carbons
How many carbons are in a medium-chained FA?
6 to 11 carbons
How many carbons are in a long-chained FA?
12 to 26 carbons
how many carbons are in fatty acids that are considered short?
2 to 4 carbons (barely a chain)
What type of fatty acids is most abundant among plants & animals?
FAs with an even number of carbon atoms in a long, unbranched chain thats anywhere between 12 to 20 carbons long.
What are the 2 forms of fatty acids?
- esterified fatty acids
- unesterified fatty acids
Which type of fatty acid is a bound fatty acid?
esterified FAs.
Are unesterified FAs also bound?
no, they are free fatty acids
Where are esterified fatty acids found?
in natural fats & oils, in lipid classes like:
- TAG (triglycerides)
- PL (phospholipids)
- CE (cholesteryl esters)
these are all components of lipoproteins
where are unesterified fatty acids found?
They are in transport form found in plasma.
Which form of fatty acid is more common?
Esterified FAs; fatty acids mainly occur as esters
What are the 2 sources of fatty acids?
- lipolysis
- lipogenesis
What is lipolysis?
It is the breakdown of natural fats.
What is lipogenesis?
It is the de novo synthesis of fatty acids
How are free fatty acids derived?
They are derivides from the hydrolysis of:
1. animal fats
2. vegetable oils
3. phospholipids of biological membranes
What is Denovo synthesis?
It is the synthesis of fatty acids from other sources.
What is the function of free fatty acids?
FFAs play an important role in both the structure & function of cells.
contribute to:
1. structural integrity
2. energy metabolism
3. various physiological functions
What are the functions of fatty acids?
- source of energy by various tissues (heart & skeletal muscle)
- fatty acids are transported to the liver for further metabolism
- fatty acids are involved in: regulating inflammation, insulin sensitivity, & gene expression
- fatty acids can function as signalling molecules, influencing: inflammation, immune responses, & overall metabolic pathways.
what is the melting point of fatty acids?
- solid FAs: high mp
- liquid FAs: low mp
When is a fatty acid solid/ has a high mp?
When it is long & saturated
When is a FA liquid/ has a low mp?
when it is short & unsaturated?
So what is the relationship of all these factors in fatty acids?
- ↑ chain length & ↑ saturation = ↑ melting point = ↑ solidity & ↓ fluidity
- ↓ chain length & ↓ saturation = ↓ melting point = ↓ solidity & ↑ fluidity
mp increases as the no. of carbon chains…
increases
melting point increases as no. of double bonds…
decreases
the greater the degree of unsaturation…
the lower the melting point
……. fatty acids are solid
saturated
Unsaturated FAs have a …. mp than their saturated counterparts.
lower
…. fatty acids are liquid
unsaturated
What is an example of saturated fatty acids?
- adipose tissue
- butter
what is an example of unsaturated fatty acids?
- cell membrane
- olive oil
What do membrane lipids contain?
polyunsaturated fatty acids. (PUFA)
fatty acids
How are carbons numbered?
to designate the position of the double bonds (if present)
What are the 2 systems used to designate the position of double bonds?
- delta numbering system
- omega numbering system
What is the delta numbering system?
- aka C-system
- carbons are numbered beginning at first carbon
- the position of double bond is represented by the delta symbol, Δ, followed by a superscript number.
What is the first carbon called?
carboxyl carbon aka carboxyl terminus, i.e. delta carbon.
What is the omega numbering system?
- also called n-system
- carbons are numbered from the last carbon (terminal carbon)
Who is the omega numbering system mainly used by?
It is widely utilized by nutritionists.
What is another name for the last carbon?
methyl carbon aka omega carbon.
Where do the unsaturated fats belong?
Unsaturated fats naturally take place at the following series:
- ω -9
- ω -6
- ω -3
In this example, where is the double bond according to the delta & omega numbering systems?
- in delta: ∆ 9, meaning db is between C 9 & 10
- in omega: ω 7, meaning db is between carbons 7 & 8 in the omega system
what are the carbons adjacent to the carboxyl carbon referred to as?
the one directly next to the carboxyl carbon (so carbon 2) is the α carbon, while carbon 3 is the β carbon. (carbon 2 & 3 in delta system)
Where is the methyl carbon and what is it called?
It is at the distal end & is called the omega carbon.
How is the position of the double bond specified?
By a ∆ followed by a superscript number.
What is the short-handed formula of fatty acids?
It is the formula that gives information about the fatty acid like:
1. no. of carbons in FA
2. no. of double bonds in FA
3. position of double bonds in FA
What is the format of short-handed formula?
no. of C atoms : no. of bd (position of double bond)
What is the short-handed formula of this fatty acid using delta numbering system?
18 : 2 (∆ 9,12)
What is the short-handed formula of this fatty acid using omega numbering system?
18: 2 (ω 6,9)
What is the system for fatty acid nomenclature?
The Genevan Naming System names the hydrocarbon chain & replaces e with anoic acid acid.
Saturated vs. unsaturated fatty acids naming?
- Saturated fatty acids end in anoic
ex. pentanoic acids - unsaturated fatty acids end in enoic
ex. pentenoic acid
What is the formula of the fatty acid below?
Genevan name: octa dec tri enoic acid
delta numbering system: 18:3 (∆9,12,15)
omega numbering system: 18:3 (ω3,6,9)
How are fatty acids classified?
according to their hydrophobic chain.
1. straight chain fatty acids
2. cyclic fatty acids
3. branched chain fatty acids
4. substituted fatty acids
What are straight chain fatty acids?
- aka linear fatty acids
- straight fatty acids are more common
- natural fats are usually straight & their derivatives are even
How are straight FAs sub-classified?
- saturated FAs
- unsaturated FAs
What are cyclic chain FAs?
- FAs that bear cyclic groups
- less abundant than straight FAs
where are cyclic FAs found?
in some bacteria & seeds lipids.
What is an example of a cyclic FA?
hydnocarpic acid
What are branched chain FAs?
- FAs bearing a carbon branch
- less abundant than straight FAs
examples of branched chain FAs?
- isobutyric acid
- isovaleric acid
what are substituted chain FAs?
- FA bearing a substituent group
- less abundant than straight FAs
- have 1 or more hydrogens that have been changed into another group
what are examples of substitued chain FAs?
- lactic acid of blood
- ricinoleic acid of castor oil
- cerebonic, nervonic, & oxy-nervonic acids of brain glycolipids
What is the short-hand formula of nervonic acids?
(24:1, n-9)
nervonic acids are mainly found in white matter of animal brains & myelin sheaths of peripheral nerve fibres that are enriched by sphingolipids.
What are the 2 sub-classifications of fatty acids?
- saturated fatty acids
- unsaturated fatty acids
What are the properties of saturated fatty acids (SFA)?
- only have single bonds
- contain NO double bonds
- solid at room temperature
- straight chains
what are the properties of unsaturated fatty acids (UFA)?
- have double bonds
- contain one or more double bonds
- liquid at room temperature
- cis (bent) and trans (straight)
What is unique about unsaturated FAs?
unlike saturated fatty acids, the kink/ bend in the chain of unsaturated FAs prevents from packing together closely and results in:
- weaker intermolecular forces
- lower melting points
- increase in fluidity of biological membranes
What are the subclassifications of saturated FAs?
- even saturated chain FA
- odd saturated chain FA
What are even saturated chain FA?
carry an even number of carbons
What are odd saturated chain FA?
carry an odd number of carbons
What are the 2 examples of odd sat. chain FA?
with short-hand formula
- propionic acid 3:0
- valeric acid 5:0
What are the even sat. chain FA?
in order of no.
- acetic acid [2:0]
- butyric acid [4:0]
- caproic acid [6:0]
- caprylic acid [8:0]
- capric acid [10]
- lauric acid [12:0]
- myristic acid 14:0
- palmitic acid 16:0
- stearic acid 18:0
- arachidic acid 20:0
- behenic acid 22:0
- lignoceric acid 24:0
12:0
lauric acid
6:0
caproic acid
20:0
arachidic acid
What is the most abundant saturated fatty acids?
in the body, the most abundant saturated fatty acids are:
1. palmitic acid [16:0]
2. stearic acid [18:0]
where are the FAs with 4-10 carbons found in significant quantities?
milk
What are primarily composed of fatty acids with at least 16 carbons?
structural lipids & TAG (triglycerides)
unsaturated fatty acids
What are methylene interruptions?
When a fatty acid has more than 1 double bond.
How do methylene interruptions occur?
when the double bonds are separated by a methyl group
What is key to polyunsaturated fatty acids?
They are never conjugated
What is an example of a methylene interruption?
-CH=CH-CH2-CH=CH-
What are the 2 configuarions of double bonds in fatty acids?
- Cis configuration
- Trans configuration
What do the configurations of a double bond in FAs result in?
geometric isomerism
Which configuration is more common?
Cis config.
Where are the hydrogen bonds in cis config.?
hydrogens are on the same side of the double bond
where are the hydrogens in a trans config.?
on opposite sides of the double bond
what does a cis config cause?
results in a bend (kink) in the fatty acid.
What is the kink angle in cis config.?
120 degrees
What is the kink angle in trans config.?
None, there is no kink in FA.
i.e. trans FA is straight/linear
Which fatty acids are healthy?
cis fatty acids.
What is an example of unhealthy fat?
hydrogenated fats, like margine. Those have a trans config. unsat. fatty acid
Which config. of unsat. fatty acids is more common?
the cis isomer predominates.
- is is also more naturally occurring in foods
what does 1 cis double bond look like?
they form an L-shape
What does more than one cis double bond look like?
the double bond folds back into a U-shape.
How are unsaturated chain fatty acids classified?
- MUFA (monosaturated FA)
- PUFA (polyunsaturated FA)
What are the properties of MUFA?
- monoenoic
- carry 1 (single) double bond
what are the properties of polyunsaturated fatty acids? (PUFA)
- polyenoic
- consists of 2 or more (several) bonds
What is the shorthand formula for palmitoleic acid?
with omega position of db
- 16:1 ∆ 9
- ω 7
What are 2 examples of MUFA?
- palmitoleic acid
- oleic acid
What is the shorthand formula for oleic acid?
- 18:1 ∆ 9
- ω 9
What are the properties of oleic acid?
with formula
- 18 carbon atoms & 1 db
- formula is CH3-(CH2)7-CH=CH-(CH2)7-COOH
- oleic acid is the most common fatty acid in human tissue
- found in olive oil, many nuts, & seeds
- formed in the body from stearic acid
- oleic acids are L-shaped
Why is olive oil healthy?
Because it lowers the risk of cardiovascular disease & inflammation
- contains oleic acid, a MUFA derived from SFA stearic acid.
What are examples of PUFA?
UFA with more than one db
- linoleic acid
- α-linolenic acid
- arachidonic acid
- EPA
- DHA
What is the shorthand for each PUFA mentioned?
with omega
- 18:2 ∆ 9,12 [ω6]
- 18:3 ∆ 9,12,15 [ω3]
- 20:4 ∆ 5,8,11,14 [ω6]
- 20:5 ∆5,8,11,14,17 [ω3]
- 22:6 ∆4,7,10,13,16,19 [ω3]
What type of acid is a linoleic acid?
with properties
It is a dienoic acid, having 2 double bonds.
- present in soybean, sunflower, & groundnut oil.
What type of acid is linolenic acid?
It is a trienoic acid, meaning it has 3 double bonds.
- present in linseed oil
What type of acid is arachidonic acid?
Tetraenoic acid, meaning it has 4 double bonds.
- present in groundnuts & cell membrane
- it is a precursor for prostaglandins
True/False: humans do not synthesize most of the fats from other fats & fat substitutes
False; the human body can synthesize most fats from other fats/ fat substitutes
Which fats are essential fatty acids?
PUFA: poly unsaturated fats, specifically:
- linoleic & alpha-linolenic acids
What are the 2 classifcations of essential fatty acids?
- omega-3
- omege-6
Why are these essential fatty acids?
Omega-3 & Omega-6 Fatty acids are precursors to Eicosanoids, which are critical in:
- inflammatory responses
- (other) physiological functions
Where are omega 3 fatty acids found?
- fatty fishes: salmon, sardines, tuna, cod liver oil
- eggs
- flaxseeds
- greeny leafy vegetable
- walnuts
- soyabean
Where are omega-6 fatty acids found?
- fish
- egg
- meat
- poultry
- corn
- nuts
- soyabean oils
- oil seeds
What is the omega series of natural unsaturated fats?
ω-9, ω-6 and ω-3 series
What are the overall top 3 most abundant fatty acids?
- palmitic acid
- stearic acid
- oleic
