lipids

Question 1

What are the components of triglycerides?

Answer 1

• A glycerol molecule.
• 3 fatty acid chains.

Question 2

What are the components of phospholipids?

Answer 2

• A glycerol molecule.
• A phosphate group.
• Two fatty acid chains.

Question 3

How are triglycerides formed? What is produced as a by-product of this reaction?

Answer 3

• Triglycerides are formed via the condensation of one molecule of glycerol and 3 molecules of fatty acid (ie. three different condensation reactions occur.)
• 3 molecules of water are produced by this condensation reaction.

Question 4

Atoms involved in ester bond?

Answer 4

– COO

Question 5

Explain what happens to glycerol and fatty acids in a condensation reaction to make a triglyceride + 3 water molecules.

Answer 5

• Ester bond formed by condensation reaction between three OH groups on glycerol and the OH group of each fatty acid chain (releasing 3 molecules of water, leaving 3 ester bonds on triglyceride.)

Question 6

What are the 2 groups of lipids?

Answer 6

• Phospholipids.
• Triglycerides.

Question 7

What is the general formula of a fatty acid?

Answer 7

• (RCOOH)
• (R means varibale group - the number of carbons and hydrogens can change.)

() - extra for clarification

Question 8

FInish the sentence.

The R group of a fatty acid can be ……… or ……….

Answer 8

• Saturated
• Unsaturated.

Question 9

Definition of: saturated fatty acids.

Answer 9

• The hydrocarbon chain has only single bonds between carbons.

Question 10

Definition of: unsaturated fatty acids.

Answer 10

• The hydrocarbon chain consists of at least one double bond between carbons.

Question 11

In phospholipids, what are one of the fatty acids of the triglyceride substituted by.

Answer 11

• Substituted by a phosphate- containing group.

Question 12

Why do triglyceride’s structure help them store energy well?

Answer 12

• Due to the large ratio of energy-storing carbon-hydrogen bonds compared to the number of carbon atoms.
  (those carbon-hydrogen bonds store a lot of energy.)

() - extra info for clarification.

Question 13

What structure do triglyceride’s have that allow them to be a “metabolic water source?”

Answer 13

• Molecules have a high ratio of hydrogen to oxygen atoms - act as metabolic water source.
• Triglycerides can release water when oxidised (essential for animals in desert.)

Question 14

What is meant when we say triglycerides are non-polar molcules, how does this help them?

Answer 14

• Triglycerides non-polar (have no chargee) making them insoluble in water.
• A large amount can be stored/ won’t affect water potential. No osmosis of water into cell.

Question 15

Why is it useful that lipids have a relatively low mass?

Answer 15

• Helps with them being energy-storage molecules.
• A lot of molecules can be stored without increasing the mass/ preventing movement.

Question 16

True or False

Lipids have a relatively high mass.

Answer 16

• False.
• Lipids have a relatively low mass.

Question 17

True or False

Triglycerides are polar molecules.

Answer 17

• False.
• Triglycerides are non-polar molecules (helps them be insoluble in water.)

Question 18

Steps of emulsion test.

Answer 18

• Dissolve sample (oil/ fat) in ethanol and shake.
• Add distilled water and shake.
• Positive test: white emulsion/ cloudy-white if a lipid is present.

Question 19

How are phospholipids formed?

Answer 19

• Two fatty acid chains bond to the glycerol via two condensation reactions; resulting in 2 ester bonds formed.

Question 20

What type of head do phospholipids have? What does this mean? Why do phospholipids have this type of head?

Answer 20

• A hydrophillic “head.”
• The head is attracted to water.
• Due to the fact the phosphate- (containing) group is charged.

Question 21

What does hydrophillic mean?

Answer 21

• Section of a molecule which is attracted to water.

Question 22

Hydrophobic meaning.

Answer 22

• Section of molecule which is repelled by water (ie. moves away from water.)

Question 23

What is the property of the fatty acid chains/ the tails in phospholipids? What does this mean? Why do phospholipids have this type of tail?

Answer 23

• It is hydrophobic.
• It is repelled by water.
• Because the fatty acid chain is NOT charged.

Question 24

What are polar molecules?

Answer 24

• Molcules that have an overall charge (ie. each end of the molecule has its own charge.)

Question 25

Can fatty acids mix with lipids, how about phosphate groups?

Answer 25

- Phosphate groups --> repel lipids (charged.) - Fatty acids --> Mix/ interract with lipids.

Question 26

How do phospholipids position themselves in water?

Answer 26

- They form double-layer in water. - Heads facing outwards (towards water ie. water of cytoplasm/ water in tissue in membranes.) - Tails facing inwards (away from water/ shielded from the aqueous environment.)

Question 27

What is the double-layer that phospholipids form when they are in water called?

Answer 27

- Phospholipid bilayer.

Question 28

What is the property of the centre of the phosphlipid bilayer? How does this help?

Answer 28

- Hydrophobic (repels water) so that substances cannot easily pass through. - Creates a barrier between inside and outside of cell and allows for separation of solutions.

Question 29

What does hydrolysis of triglyceride produce?

Answer 29

- 1 molecule of glycerol. - 3 fatty acid chains.

Question 30

Why is it useful to have a hydrophillic phosphate head (attracted to water?)

Answer 30

- Helps hold the bilayer at the surface of the cell- surface membrane (because the phosphate head pulls away - attracting to water.)

Question 31

What is the name of this group (---- COOH) that is found in all fatty acids?

Answer 31

- Carboxyl group.

Question 32

What do we call fatty acid chains that contain 1 carbon-carbon double bond only?

Answer 32

- Mono- unsaturated chain.

Question 33

From diagrams, if there are no double bonds, how can you tell if fatty acid chain is saturated vs unsaturated?

Answer 33

- Unsaturated: will have a kink/ bend. - Saturated: will be straight

Question 34

# (past paper Q) Difference between triglyceride/ phospholipid.

Answer 34

- Phospholipid: fatty acid replaced by phosphate group.

Question 35

Similarities in structure of triglycerides and phospholipids.

Answer 35

- Both contain ester bonds. - Both contain glycerol. - Both contain fatty acids that can be saturated/ unsaturated. - Both are insoluble.