Lipids: Structure & Function

Question 1

Lipids as energy stores

Answer 1

• Long hydrocarbon chains
• When triglycerides are oxidised in cellular respiration the bonds are broken which release energy to produce ATP
• Hydrophobic so do not cause osmotic uptake of water in cells, so more can be stored
• Plants store them as oils in seeds and fruits
• Oxidation of C-H bonds released lots of water molecules (can be used by desert animals)

Question 2

Lipids as insulators

Answer 2

• Myelin sheath around axons
• Increases speed of transmission of nerve impulses
• Fat below skin keeps mammals warm

Question 3

Lipids in buoyancy

Answer 3

• Low density of fat tissue increases ability for animals to float more easily

Question 4

Lipids as protection

Answer 4

• Fat below skin prevents organs from being damaged as easily
• Cushions impacts

Question 5

Phospholipids structure and function

Answer 5

• Hydrophobic core of fatty acid tails
• Hydrophilic phosphate heads form H bonds with water
• Allows compartmentalisation
• If there are lots of saturated fatty acid tails then membranes are less fluid

Question 6

Cholesterol structure and function

Answer 6

• In phospholipid bilayer
• Affects fluidity of membrane by disrupting close packing
• Acts as barrier between phospholipids preventing water soluble molecules from diffusing through membrane
• Also used to produce steroid-based hormones