Lipids

what elements do lipids contain

cabon, hydrogen, oxygen

what are the two types of lipids

triglycerides and phospholipids

why are lipids not polymers

because they are made up of different molecules joined together

describe triglyceride molecules

• have 3 fatty acids joined to one glycerol molecule

• joined in three condensation reactions with the loss of three water molecules

What forms an ester bond

A condensation reaction between a glycerol and fatty acids (R-COOH)

How many ester bonds does one triglyceride molecule have

3 ester bonds

• Properties of lipids

• Insoluble in water

• Solid or liquid at room temperature

• Soluble in organic solvent eg alcohol

Roles of lipids

• Energy stores( x2 as much energy as mass of carbohydrate)

• Water proofing

• Good insulators

What’s the general formula of fatty acid

R-COOH

R stands for a long hydrocarbon chain and COOH is a carboxylic acid group

What are the two types of fatty acids

Saturated and unsaturated

What’s the difference between a Saturated and unsaturated fatty acid

Saturated: no double bonds between carbon atoms

Unsaturated: on or more double bonds between carbon atoms

How can lipids be hydrolysed into fatty acids and glycerol

• heating up with acid or alkali

• Using the enzyme lipase at it’s optimum temp and ph

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Roles and properties of triglycerides

• non-polar molecules and insoluble in water (osmotically inactive as they are ideal for storage)

• high ratio of hydrogen to oxygen atoms, releasing water when respired

• possess a high proportion of carbon-hydrogen bonds so that they release twice as much energy as carbohydrates during aerobic respiration

what are phospholipids?

lipids containing a phosphate group

describe phospholipid molecules

• consists of one glycerol, two fatty acids and a phosphate group joined by a condensation reaction.

• have a polar hydrophilic head (attracts water) containing the phosphate group and a non-polar hydrophobic tail (repels water) consisting of long fatty acids chains

word formula for phospholipid and triglyceride

• glycerol+ 2 fatty acids + phosphate= phospholipid + 3 water

• glycerol+ 3 fatty acids = triglyceride +3 water

similarities of triglycerides and phospholipids

• are insoluble in water

• contain glycerol

• contain ester bonds

• both insoluble in water

differences of triglycerides and phospholipids

• both have same elements but phospholipids contains one extra element which is P (phosphate)

• triglycerides have 3 fatty acids whereas phospholipid has 2 fatty acids

• triglycerides are non-polar and hydrophobic whereas phospholipids are polar and have a hydrophilic and hydrophobic region

why do phospholipids form a bilayer

due to the hydrophilic heads being attracted to the water on either side and hydrophobic tails being repelled by water so they face each other