Lipids

Question 1

What are the characteristics of lipids?

Answer 1

• They contain carbon, hydrogen and oxygen.
• Proportion of oxygen to carbon and hydrogen is smaller than in carbohydrates
• Insoluble in water
• They are soluble in organic solvents such as alcohol and acetone.

Question 2

What are triglycerides?

Answer 2

Lips that have one molecule of glycerol with three fatty acids attached to it.

Question 3

What reaction forms triglycerides?

Answer 3

Condensation Reactions.

Question 4

How are triglycerides formed?

Answer 4

• Fatty acid joins a glycerol molecule, an ester bond is formed and a molecule of water is released.
• Reaction occurs twice more to form a triglyceride.

Question 5

What bonds do the fatty acids form?

Answer 5

Each fatty acid forms an ester bond with glycerol in a condensation reaction.

Question 6

What is the role of phospholipids in the cell membrane?

Answer 6

Phospholipids in the cell membrane serve the following purposes:
They contribute to
• The Flexibility of the Cell Membrane.
• Transfer of lipid soluble substances across them.

Question 7

What are some key roles of phospholipids?

Answer 7

• Source Of Energy
• Waterproofing
• Protection
• Insulation

Question 8

How do phospholipids serve as a source of energy?

Answer 8

• When oxidised, lipids provide twice the energy as the same amount of carbohydrates.
• Release Water

Question 9

How do phospholipids serve as protection?

Answer 9

Fat is stored around delicate organs, this provides a layer of protection.

Question 10

How do phospholipids serve as a source of insulation ?

Answer 10

• Fats are bad conductors of heat, can be stored under the body surface to retain body heat.

Question 11

What role do phospholipids serve in nerve cells?

Answer 11

• Act as electrical insulators in the myelin sheath around nerve cells.

Question 12

What reaction breaks down triglycerides?

Answer 12

Hydrolysis

Question 13

What are the products of hydrolysis of triglycerides?

Answer 13

• Three Fatty Acids

* Glycerol

Question 14

What are phospholipids?

Answer 14

Phospholipids are membranes which consist of glycerol, two fatty acids and a phosphate group.

Question 15

What causes variation in the triglycerides?

Answer 15

• Differences in the triglycerides come from variations in the fatty acids, as all glycerol molecules in triglycerides are the same.

Question 16

What are the two types of fatty acids?

Answer 16

• Saturated

* Unsaturated

Question 17

How do saturated fatty acids differ to unsaturated fatty acids?

Answer 17

• Saturated fatty acids don’t have any double bonds between their carbon atoms.
• Unsaturated fatty acids have at least one double bond between carbon atoms

Question 18

What are triglycerides used for?

Answer 18

Energy Storage

Question 19

How are triglycerides suited to carrying out their function?

Answer 19

• Triglycerides a high ratio of carbon hydrogen atoms to carbon atoms, making them a good energy source ( Carbon hydrogen stores energy ).
• Triglycerides have a low mass to energy ratio, making them very good at storage, because much can be stored in a small space.
• Insoluble, so they do not affect water potential, and cause water to enter the cells by osmosis.
• Long hydrocarbon tails contain lots of chemical energy, when broken down they release a lot of energy.
• High ratio of hydrogen to oxygen atoms, they release water when oxidised, and therefore are an excellent source of water.

Question 20

What are the two parts that make up a phospholipid?

Answer 20

• Hydrophillic Head

* Hydrophobic Tail

Question 21

What are polar molecules?

Answer 21

Molecules that have two ends that behave differently.

Question 22

What function do phospholipids serve in the cell membrane?

Answer 22

They make up the bi-layer of cell membranes.

Question 23

How are phospholipids adapted to their purpose?

Answer 23

• Heads are hydrophilic, and tails are hydrophobic, so they form a double layer, with their heads facing out towards the water.
• Centre of bi-layer is hydrophobic, so water soluble substances cannot pass easily through it, membrane therefore acts as a barrier.
• They can form glycolipids by combining with carbohydrates inside the cell surface membrane.

Question 24

What is the test for lipids?

Answer 24

Emulsion Test.

Question 25

What is the process of the emulsion test?

Answer 25

* Shake the test substance with ethanol for a minute so that it dissolves, then pour the water solution into water. * Lipids will show up as a milky emulsion. * The more lipid there is, the more noticeable the milky colour will be.

Question 26

How do phospholipids differ to triglycerides?

Answer 26

One of the fatty acid molecules is replaced by a phosphate group.

Question 27

What parts of the phospholipid are hydrophillic, and hydrophobic?

Answer 27

* Phosphate group is hydrophilic. | * Tails are hydrophobic.