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The Structure and Function of Lipids

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The Structure and Function of Lipids


Ø Structure - hydrophobic

- Ester bonds

- Non polar


- Low density

- Insoluble in water but soluble in organic solvents

Ø Buoyancy and thermal & electrical insulation

Ø Phospholipid bilayer in cell membrane - hydrophobic/hydrophilic

Ø Protection in - kidneys

- Pathogens (Casparian strip)

Ø Honey comb

Ø Energy store - releases twice as much energy as carbohydrates per

Ø Hormones e.g. steroids

Ø Attraction - esters smell sweet this attracts pollinating insects to

Ø Waterproofing - hair

- Waxy cuticles

Write an essay about the structure and function of lipids in plants
and animals

Lipids contain carbon, hydrogen, and oxygen. Lipids are found in the
form of fats, oils, and waxes. Lipids are non polar and therefore
insoluble in water, however, they are soluble in organic solvents such
as ether. As they are non- polar it means that they have an even
distribution of charge along the molecule. As they are insoluble, they
join to form globules.

A triglyceride is a lipid formed from glycerol and three fatty acids
that are linked together by ester bonds. Each fatty acid molecule
consists of a carboxyl group -COOH. Triglycerides, which have an
unsaturated fatty acid, tend to be a liquid at room temperature and
are called oils. Those, which contain saturated fatty acid, tend to be
a solid at room temperature and are known as fats or waxes.
Triglycerides are a useful energy store in animals and plants as they
are insoluble in water as they are non -polar and can be stored inside
cells in the form of droplets. Lipids droplets are also found in
mitochondria as they have a relatively low density allowing them to
release twice as much energy per gram as carbohydrates.

Whales and other mammals, which live in water, have cells that contain
a lot of fat beneath their skin. These cells make up adipose tissue
whose function is not only to act as an energy store but also provides
the animal with buoyancy; therefore, it is important that lipids are
insoluble in water. Lipids also provide the animal with insulation.
This ensures that heat loss from the skin into the water is kept to a
minimal. Humans also have adipose tissue beneath their skin, which
also prevents heat loss, therefore it is important that lipids are
good heat insulators otherwise a lot of heat would be lost. Lipids
help to protect internal organs within the human body, such as the
kidneys, by providing a cushioning layer. This protects against
mechanical damage.

Waxes are esters of fatty acids and long chains of alcohols. The main
function of waxes and oils is to provide excellent waterproof layers.
For example, in plants the leaves are covered by waxy cuticles, which
prevent excess water loss or entry. In animals, such as ducks, oil is
found on their feathers to ensure excess water is not absorbed. In
vertebrates, a waxy layer is found on their skin and fur, which is
deposited on the outside of the cuticle in insects. Some bees are able
to synthesise their own wax, which is used to construct a honeycomb.

Phospholipids are lipids formed from glycerol, two fatty acids, and a
phosphate group. Phospholipids are found in the cell membrane. This
molecule has a hydrophobic and hydrophilic part. The hydrophobic fatty
acids part is not attracted to water and is therefore found on the
outside part of the cell membrane. The hydrophilic phosphate part is
attracted to water and is therefore found in the inner part. This
forms a phospholipid bilayer.

Glycolipids are made up of carbohydrates and lipids. The carbohydrate
component allows substances such as antibodies and hormones to
recognise it. As carbohydrates are soluble in water, they are able to
form hydrogen bonds with water, which increases the stability of the
membrane. The lipid component allows the glycolipid to become less
soluble this is found in the form of cholesterol. Excess cholesterol
is responsible for cardiovascular diseases such as heart attacks as
they cause a blocking in the coronary artery. Some hormones are also
made up of lipids and are known as steroids.

The ester bonds in lipids smell sweet this helps to attract bees to
plants, this helps pollination. Lipids are also found in hair to make
it waterproof it is able to do this, as lipids are insoluble in water.

It can be seen that lipids have many functions, which depend
enormously on its structure. It is important that they are both
saturated and unsaturated to ensure it carries out it function

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"The Structure and Function of Lipids." 20 Apr 2014

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