lipids to be able to identify the elements which make up lipidsidentify the elements which make up...

LIPIDSLIPIDS

To be able to To be able to • Identify the elements which make up Identify the elements which make up

lipids lipids • Explain that glycerol and fatty acids Explain that glycerol and fatty acids

combine by condensation to produce combine by condensation to produce triglycerides.triglycerides.

• Demonstrate why the R group of a fatty Demonstrate why the R group of a fatty acid may be saturated or unsaturated.acid may be saturated or unsaturated.

• Explain how phospholipids are formedExplain how phospholipids are formed

LIPIDSLIPIDS

• What are lipids?What are lipids?

• Why are they useful?Why are they useful?

• What is their biological use?What is their biological use?

• What elements make up lipids?What elements make up lipids?

TRIGLYCERIDESTRIGLYCERIDES

• The most common type of lipids are the The most common type of lipids are the triglycerides also known as fats and triglycerides also known as fats and oils, or TRIGLYCERIDESoils, or TRIGLYCERIDES

• Triglycerides are made from a Triglycerides are made from a combination of three fatty acid combination of three fatty acid molecules and one glycerol molecule molecules and one glycerol molecule by a condensation reaction.by a condensation reaction.

GlycerolGlycerol

Fat

ty A

cid

F

atty

Aci

d

Fat

ty A

cid

F

atty

Aci

d

Fat

ty A

cid

F

atty

Aci

d

The glycerol molecule in any triglyceride is The glycerol molecule in any triglyceride is always the same. It is the fatty acids that varyalways the same. It is the fatty acids that vary

GlycerolGlycerol is a small, is a small, 3-carbon molecule 3-carbon molecule with three alcohol with three alcohol groups. groups.

HH HH HH

OHOH OHOH OHOH

CCCCCCHH HH

Fatty acidsFatty acids are long molecules with a are long molecules with a polar, hydrophilic end and a non-polar, hydrophilic end and a non-polar, hydrophobic "tail". polar, hydrophobic "tail".

HH HH HH

HH HH HH

CCCCCCHH

HH HH

HH HH

CCCC CCOO

OHOH

Methyl Methyl GroupGroup

Hydrocarbon ChainHydrocarbon Chain

(14-22 carbon atoms)(14-22 carbon atoms)Carboxyl Carboxyl

GroupGroup

The hydrocarbon chain can be The hydrocarbon chain can be from 14 to 22 CHfrom 14 to 22 CH22 units long, but it units long, but it

is always an even number is always an even number because of the way fatty acids are because of the way fatty acids are made..made..

The hydrocarbon chain is The hydrocarbon chain is sometimes called an R group, so sometimes called an R group, so the formula of a fatty acid can be the formula of a fatty acid can be written as R-COO-written as R-COO-

General formulaGeneral formula

CHCH33 – (CH – (CH22))nn - COOH - COOH

Saturated fatty acidsSaturated fatty acids

• Saturated fatty acids only have C-C Saturated fatty acids only have C-C bondsbonds

• Each carbon in the chain is joined by a Each carbon in the chain is joined by a single bondsingle bond

• Each carbon is Each carbon is SATURATEDSATURATED with with hydrogenhydrogen

• These fatty acids form straight chains, These fatty acids form straight chains, and have a high melting points.and have a high melting points.

COOCOO--

Unsaturated fatty acidsUnsaturated fatty acids• Unsaturated fatty acids only at least Unsaturated fatty acids only at least

one C=C double bondone C=C double bond• Polyunsaturates have more than one Polyunsaturates have more than one

double bond double bond

• These fatty acids form bent chains, and These fatty acids form bent chains, and have a low melting point.have a low melting point.

COOCOO--CCCCCCCCCCCCCCCCHH

HH HH HH HH HH HH HH HH

HH HH HH HH HH HH

Formation of triglyceridesFormation of triglycerides

• One molecule of glycerol joins together One molecule of glycerol joins together with three fatty acid molecules to form with three fatty acid molecules to form a a triglyceride triglyceride molecule, in another molecule, in another condensation polymerisation reaction:condensation polymerisation reaction:

HOHO

HH

HOHO

HH

HOHO

HH

CC

CC

CC

HH

HH

CCCCCCHH

HH HH HH HH HH HH

HH HH HH HH HH HH

CC CC CC CCOO

OHOH

==

CCCCCCHH

HH HH HH HH HH HH

HH HH HH HH HH HH

CC CC CC CCOO

OHOH

==

CCCCCCHH

HH HH HH HH HH HH

HH HH HH HH HH HH

CC CC CC CCOO

OHOH

==

HH22OO

HH22OO

HH22OO

HOHO

HH

HOHO

HH

HOHO

HH

CC

CC

CC

HH

HH




3H3H22OO

OOHH

HH

HH

CC

CC

CC

HH

HH

CHCH33 – (CH – (CH22))nn - C - COO=

OOCHCH33 – (CH – (CH22))nn - C - COO=


ESTER BONDSESTER BONDS

•Phospholipids have a similar Phospholipids have a similar structure to triglycerides, but with a structure to triglycerides, but with a phosphate group in place of one phosphate group in place of one fatty acid chain. fatty acid chain. •There may also be other groups There may also be other groups attached to the phosphate. attached to the phosphate.

PhospholipidsPhospholipids

Phospholipids have a polar hydrophilic Phospholipids have a polar hydrophilic "head" (the negatively-charged phosphate "head" (the negatively-charged phosphate group) and two non-polar hydrophobic group) and two non-polar hydrophobic "tails" (the fatty acid chains)."tails" (the fatty acid chains).

HH

HH

HH

CC

CC

CC

HH

HH



OO

OO--

OO--

OOPP ==

This mixture of properties is This mixture of properties is fundamental to biology, for fundamental to biology, for phospholipids are the main phospholipids are the main components of cell membranes.components of cell membranes.

water

SteroidsSteroidsSteroids are small hydrophobic molecules Steroids are small hydrophobic molecules found mainly in animals. They include: found mainly in animals. They include: •CholesterolCholesterol, which is found in animals cell , which is found in animals cell membranes to increase stiffnessmembranes to increase stiffness•Bile saltsBile salts, which help to emulsify dietary , which help to emulsify dietary fatsfats•Steroid hormones such as testosterone, Steroid hormones such as testosterone, oestrogen, progesterone and cortisoloestrogen, progesterone and cortisol•Vitamin D, which aids CaVitamin D, which aids Ca2+2+ uptake by uptake by bones.bones.

• Why is it wrong to call lipids ‘fats’?Why is it wrong to call lipids ‘fats’?• Because saturated lipids are mainly animal fats but Because saturated lipids are mainly animal fats but

unsaturated lipids are called oilsunsaturated lipids are called oils• What is the name given to the type of bond that joins What is the name given to the type of bond that joins

fatty acids and glycerol in a lipid molecule?fatty acids and glycerol in a lipid molecule?• Ester bondEster bond• Why are lipids insoluble in water?Why are lipids insoluble in water?• Because they have a hydrophobic tail that repels Because they have a hydrophobic tail that repels

water and this causes the molecules to clump water and this causes the molecules to clump together to reduce the surface area in contact with together to reduce the surface area in contact with water.water.

• Describe the difference between a triglyceride and a Describe the difference between a triglyceride and a phospholipid. How do these differences affect the phospholipid. How do these differences affect the properties of the molecule?properties of the molecule?

• A phosphate group replaces one of the fatty acid A phosphate group replaces one of the fatty acid moleculesmolecules

• The phosphate group is ionised which makes it The phosphate group is ionised which makes it attract water molecules. This end is therefore attract water molecules. This end is therefore hydrophilic as opposed to the fatty acid group which hydrophilic as opposed to the fatty acid group which is hydrophobicis hydrophobic

lipids to be able to identify the elements which make up lipidsidentify the elements which make up...

Documents