Revision notes topic questions past papers

against heat loss (eg. blubber of whales)

Buoyancy

The low density of fat tissue increases the ability of animals to float more easily

Protection

The adipose tissue in mammals contains stored triglycerides and this tissue helps protect

organs from the risk of damage

Exam Tip

It is common to be asked why triglycerides are energy reserves (they store more energy per

gram due to their hydrocarbon chains).

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CIE AS Biology (9700) 2019-2021 Revision Notes

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2. Biological Molecules

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CIE AS Biology (9700) 2019-2021 Revision Notes

savemyexams.co.uk

2. Biological Molecules

YOUR NOTES

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CIE AS Biology (9700) 2019-2021 Resources

REVISION NOTES 

 

  TOPIC QUESTIONS 

 

  PAST PAPERS

Page 39

2.2.6 PHOSPHOLIPIDS

The Vital Role of Phospholipids

Structure

Phospholipids are a type of lipid, therefore they are formed from the monomer glycerol and

fatty acids

Unlike triglycerides, there are only two fatty acids bonded to a glycerol molecule in a

phospholipid as one has been replaced by a phosphate ion (PO

4

3-

)

As the phosphate is polar it is soluble in water (hydrophilic)

The fatty acid ‘tails’ are non-polar and therefore insoluble in water (hydrophobic)

Phospholipids are the major components of cell surface membranes. They have fatty acid

tails that are hydrophobic and a phosphate head, that is hydrophilic, attached to a