Lipids

Question 1

What are the 2 groups of lipids

Answer 1

Triglycerides and phospholipids

Question 2

How are triglycerides formed

Answer 2

By the condensation of one molecule of glycerol and 3 fatty acid molecules which removes 3 water molecules to form ester bonds

Question 3

Why are triglycerides not polymers

Answer 3

Because they arnt made of the same monomers

Question 4

What do fatty acid chains consist of

Answer 4

Hydrocarbon chain and a carboxylique acid group
They vary in length and can be referred to as “R”

Question 5

What can the entire fatty acid be referred to as

Answer 5

RCOOH

Question 6

What happens during the formation of triglycerides

Answer 6

3 fatty acids join to the glycerol molecule via condensation reaction
Each time an ester bond is produced
A water molecule is a by product of each reaction. This means for every triglyceride molecule produced 3 water molecule are produced

Question 7

What is a saturated fatty acid

Answer 7

Don’t have any double bonds between carbon atoms in the hydrocarbons chaisn

Question 8

What is an unsaturated fatty acid

Answer 8

Have double bonds between carbon atoms in the hydrocarbon chain

Question 9

What are the properties of triglycerides

Answer 9

Long hydrocarbon fatty acid chains- contain lots of stored chemical energy which is used as an energy storage molecule
Hydrophobic fatty acid tails- insoluble in water and doesn’t affect water potential of a cell and won’t dissolve when in contact with water

Question 10

What does hydrophobic mean

Answer 10

Repeals water which makes lipids insoluble in water

Question 11

What are the fatty acid tails

Answer 11

Hydrophobic so They face inwards shielding themselves from water with their glycerol heads

Question 12

What is the difference between phospholipids and tryglicerides

Answer 12

One of the fatty acids is replaced by a phosphate group so the glycerol combined with 2 fatty acids and 1 phosphate groip

Question 13

What does a phosphate group have

Answer 13

Phosphate group has negative charge (polar) whereas the fatty acid tails don’t have a charge (non polar)
This allows the phospholipids to form a bolster in water

Question 14

How are phospholipids arranged

Answer 14

The hydrophobic fatty acid tails are arranged in the middle away from water and the hydrophilic phosphate heads are arranged onthe outside in contact with water

Question 15

Describe and explain how the phospholipids are arranged in a cell membrane

Answer 15

In a cell surface membrane phospholipids form a bilayer. The phosphate heads face outside the cell in contact with water because they are hydrophilic. The fatty acid tails face inwards away from the water because they are hydrophobic

Question 16

What is the functions of phospholipids

Answer 16

Hydrophoci fatty acid tails and hydrophilic phosphate heads. This will form a phospholipid bilayer with hydrophobic fatty acid tails pointing in away from the water and hydrophilic phosphate heads pointing towards the water. This is useful because it forms cell membranes and the hydrophobic fatty acid centre means that water soluble molecules can’t easily pass across the membranes

Question 17

What is the name of the test for lipids

Answer 17

The emulsion test

Question 18

What is the method for the emulsion test

Answer 18

Add 2 cm ethanol and shake (dissolves the lipids)
Then add water drop wise and shake
If lipids are present a white emulsion will be visible

Question 19

How can you evaluate conclusions in graphs

Answer 19

Advantages- shows a correlation and relationship
Disadvantages- can be due to another factor
Only one investigation so many not be representative
Could be a time issue or due to weather
Only on one farm