Lipids

General formula for fatty acids

CnH2n+1COOH

When fatty acids are not attached to other molecules they are called

Free fatty acid

Why are fatty acids considered to be amphipathic compounds

They have a hydrophilic carboxylic group and hydrophobic aliphatic tail

Which part of fatty acid is hydrophilic?

COOH ; carboxylic group

Which part of the fatty acid is hydrophobic?

Aliphatic tail

What number (even / odd) straight chain fatty acids are found abundantly in plant and animals

Even number straight chains

Example of fatty acid with 16 carbons

Palmitic acid

Example of fatty acid with 18 carbon is

Stearic acid

What possess the ability to synthesize odd- and branched-chain fatty acids?

Bacteria

Why ruminant animal fat contains odd-numbered fatty acids(15)

Due to the action of bacterial in the rumen

What are saturated fatty acids?

Saturated fatty acids are fatty acids where there hydrocarbon chain contains no double bonds.

Butyric (n-butanoic) can be found in

Butter

Caproic (n-hexanoic) can be found in ?

Coconut

Palm oils

Caprylic (n-octanoic)

Coconut

Palm oil

Capric (n-decanoic)

Coconut

Palm oil

Lauric (n-dodecanoic)

Laurel oil

Spermaceti

Myristic (n-tetradecanoic)

Butter

Fats

Palmitic (n-hexadecanoic)

Palm tree

Animal

Plant fats

Stearic (n-octadecanoic)

Animal

Plant fats

Arachidic (n-eicosanoic) 20 carbons

Groundnut oil

Behenic (n-docosanoic)

Groundnut oil

Lignoceric (n-tetracosanoic)

Groundnut oil

Rapeseed oils

Cerotic (n-hexacosanoic)

Wool fat

What are unsaturated fatty acids?

Fatty acids that contain double bonds in there hydrocarbon chains

What is a unsaturated fatty acid with one carbon carbon double boned called?

Monoethanoid acids

What is an unsaturated fatty acid with two carbon carbon double boned called?

Diethanoid acids

What is an unsaturated fatty acid with three carbon carbon double boned called?

Triethanoid acid

What are essential fatty acid?

They are fatty acid the body is unable to synthesis but is necessary for the human diet. As it helps with memory, helps with skin, help to reduces cardiac problem and builds immunity

Where do fatty acids bend?

They bend at the carbon carbon double bond

Why are linoleic acid and linolenic acid considered essential fatty acids

Because they are unable to be synthesis by the body. The body contain the enzyme 4,5,6,9 desaturase meaning they are unable to form double bonds any other place other than carbon 4,5,6 and 9. In linoleic there is a carbon carbon double bond at carbon 12 which the enzyme is unable to form a double bond there. In linolenic acid there is a carbon carbon double bond at carbon 12 and carbon 15; where the enzyme is unable to form a bond there.

Linolenic acid is what type of omega acid?

Omega 3 fatty acid

Linoleic acid is what type of omega fatty acid

Omega 6 fatty acid

Many naturally occurring fatty acids contain

2-3 double bonds in the cis position

Why do carbon chain of saturated fatty acids tend to be fully extended?

To minimize the repulsion between neighboring methylene groups

What type of fatty acids are solid ?

Saturated fatty acids because they do not have any bend in there chain and are tightly packed together, hence having stronger Van der Waals attractions compared to unsaturated fatty acids

Why do unsaturated fatty acid have a lower melting and boiling point than saturated fatty acids?

Unsaturated fatty acids are not tightly packed together, they have double bonds in there chain that causes rigid bends in the chain that interferes with the packing causing weaker Van der Waals forces of attraction between molecules.

Unsaturated fatty acids appears as _____ at room temperature?

Liquid

Where are saturated fatty acid found?

In animals

Where are unsaturated fatty acid found?

In plants

Where are saturated fatty acids stored?

Liver

Bone

Where are unsaturated fatty acid stored?

Seed

Fruits

Effect of oxidative rancidity on saturated fatty acid

Observed less frequency

Effect of oxidative rancidity on unsaturated fatty acid

Observed more frequently

Fatty acids are important sources of ?

Fuel

When metabolized what do fatty acids yield?

Large quantities of ATP

What organs in the body does fatty acids fuel?

Heart

Skeletal muscle

Where are enzymes responsible for desaturating fatty acids found?

In the endoplasmic reticulum

How does desaturase enzyme work?

Adding cis double bonds

How is the body abl to convert Stearic acid to oleic acid

When the enzyme 4,5,6,9 desaturase inserts a double bond but is incapable of inserting further double bonds.

How can unsaturated fatty acids from vegetable oil have their double bond removed?

By adding hydrogen (Hydrogenation)

What are hydrogenated fat?

Saturated fat even though derived from vegetable oil.

What happens when unsaturated fatty acids react with gaseous hydrogen?

Forms saturated fatty acid

What reagent or agents are need for the hydrogenation of unsaturated fatty acids?

Hydrogen gas

Catalyst : nickel, Pt

What is partial hydrogenation?

When a little of hydrogen gas is used to convert some of the carbon carbon double bonds to single bonds but not all. The unsaturated bonds that remain that were normally in the cis position are changed to the trans position.

Partial hydrogenation forms what type of compounds?

Semi solid trans unsaturated compounds

Complete hydrogenation of unsaturated fatty acids forms what type of compounds?

Solid saturated compounds

What is hydrogenation of fatty acids used for?

Manufacture of:

Candles

Vegetable shortening

Margarines

Trans fat have what type of shape?

More linear shape

Why do trans fat have a linear shape?

Because trans compounds are able to interlock, hence are able to be tightly packed together.

Benefit of trans fat

Give products longer shelf life

Negative impact of trans fat

Raises bad cholesterol (low density lipoprotein)

Why is complete hydrogenation of fatty acid avoided?

Because saturated fatty acids are hard and brittle

What is halogenation of unsaturated fatty acid?

Halogens can be added to unsaturated fatty acids at room temperature

Oxidation of unsaturated fatty acid can form?

Two aldehyde

If unsaturated fatty acid is exposed to excess oxygen what is formed?

Two carboxylic acids

What happens to unsaturated fatty acid when comes in contact with KMnO4 under mild conditions?

The glycols are formed at the sites of double bonds

What happens to unsaturated fatty acid when comes in contact with KMnO4 under vigorous conditions?

The reagent cleaves the molecules at the double bond and oxidizes the terminal portions to the carboxyl groups.

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Hence two carboxylic acids are made.

What is the oxidative rancidity of highly unsaturated oils?

Highly unsaturated oils are spontaneously oxidized by atmospheric oxygen and ordinary temperatures.

Example of an oil that is less susceptible to oxidative rancidity

Olive oil

Example of an oil that is more susceptible to oxidative rancidity

Flax seed oil

Is oxidative rancidity of fatty acids a slow or fast reaction

Slow reaction

Oxidative rancidity of unsaturated oils causes or forms?

Short chain fatty acids and aldehyde resulting in a rancid odor or taste to the fats.

Function of lipids

Store energy

Function of lipids

Acts as food storage

Are lipids soluble or insoluble?

Insoluble

Function of lipids

Membranes structure involvement

Function of lipids

High insulating capacity

Function of lipids(phospholipids)

Absorption and transport of fatty acids

Function of lipids (Cholesterol)

Play a role in hormone synthesis

Function of lipids (Vitamin A, D,E,K)

Carriers of fat soluble vitamins

Function of lipids (Squalamine - steroid found in sharks)

Antibiotic agent

Function of lipids

Aid to waterproof the body

Classification of Lipids

1. Simple lipids

2. Compound lipids

3. Derived lipids

Another name for simple lipids

Homolipids

Another name of compound lipids

Heterolipids

Example of homolipids

Triacylglycerol

Oils

Waxes

Example of heterolipids

Phospholipids

Glycolipids

What are derived lipids?

Lipids formed or derived from simple and compound lipids

Example of derived lipids

Steroids

Eicosanoids

Fat soluble vitamins

Saponifiable lipids

Formation of soaps, must have linkage present

For soponifcation of lipids to take place you need?

Sodium hydroxide

What is the most abundant of all lipids

Triacylglycerol

What makes up 98% of total dietary lipids?

Triacylglycerol

The remaining 2% of dietary lipids are?

Phospholipids

Cholesterol

Triacylglycerol Is the major component of what?

Fat storage in plant and animal cells mainly in adipocytes

Why are Triacylglycerol much better adapted than glycogen to serve as a storage form of energy?

They are longer to digest and have a greater satiety value

Are Triacylglycerol Polar or non polar?

Non polar

Are Triacylglycerol Soluble to insoluble in water?

Insoluble

Are Triacylglycerol less dense or more dense than water?

Less dense they float

How are Triacylglycerol formed?

Via esterification. Reaction between an alcohol glycerol and a tricarboxylic acid.