3.5 Lipids

Question 1

What is a triglyceride and what does it consist of?

Answer 1

• Type of lipid used as an energy store in animals, plants, and some bacteria
• Consists of glycerol backbone attached to 3 fatty acid tails.

Question 2

What features of triglycerides allow them store energy efficiently

Answer 2

• Long hydrocarbon tails - many carbon-hydrogen bonds can be broken to release energy
• Low mass to energy ratio - lots of energy can be stored in a small volume
• Insoluble - they do not affect the water potential of cells as they are large and non-polar
• High ratio of H to Oxygen atoms - triglycerides will release when oxidised

Question 3

What group of molecules to fatty acids belong to and what do they consist of

Answer 3

carboxylic acid - carboxyl group + hydrocarbon chain attached

Question 4

What happens when the hydroxyl group in the fatty acid and glycerol react

Answer 4

• Formation of 3 water molecules
• ester bonds between gylcerol + fatty acids

Question 5

What is another word for the condensation reaction between glyercol + fatty acids

Answer 5

Esterification

Question 6

What is the name given to a fatty acid chain with no double bond present between the carbon atoms

Answer 6

unsaturated

Question 7

What is the name given to a fatty acid chain with ONE double bond present between the carbon atoms

Answer 7

Monosaturated

Question 8

What is the name given to a fatty acid chain with TWO OR MORE double bond present between the carbon atoms

Answer 8

Polysaturated

Question 9

What does the presence of carbon double bond cause the fatty acid to do

Answer 9

Kink/bend, therefore cannot pack closely together

Question 10

Define structure of phospholipid

Answer 10

-Modified triglyceride
- contains element phosphorus
- One of fatty acid chain in triglyceride molecule replaced with phosphate group
-Non-polar tail, polar/charged head

Question 11

Where are phospholipids found?

Answer 11

Cytoplasm of every cell

Question 12

Why are phosphates soluble in water?

Answer 12

Phosphate ions have extra electrons and so are negatively charged

Question 13

Non-polar

Answer 13

• Not charged so repelled by water
• Mix readily with fat
• Hydrophobic

Question 14

Charged/polar

Answer 14

• Attracted to water
• Hydrophillic

Question 15

How do Phospholipids interact with water and what name are they given because of this

Answer 15

• Form a layer in water with heads in water and tail sticking out
• surface acting agents/surfactants

Question 16

Biological role of lipids

Answer 16

• membrane formation and creation of hydrophobic barriers
• hormone production
• electrical insulation necessary for impulse transmission
  -waterproofing

Question 17

Roles of lipids as long-term energy stores:

Answer 17

• thermal insulation to reduce heat loss
• cushioning to protect organs
  -buoyancy for aquatic animals