Lipids

Question 1

Triglycerides

Answer 1

Three fatty acids with an ester bond parallel to a glycerol molecule. This happens during a condensation reaction with water as a product.
-COOH- functional group

Question 2

Hydrocarbon tail of fatty acids

Answer 2

The hydrocarbon tails and hydrophobic which makes the lipids insoluble in water. (The hydrocarbon tail may vary)

Question 3

Saturated fats

Answer 3

If the chain contains single bonds (only between carbon molecules) in the chain and has a max number of carbon hydrogen bonds. (These layers pack closely together and make the molecule flat)

Question 4

Monounsaturated fats

Answer 4

One double bond between carbons in the hydrocarbon tail

Question 5

Polyunsaturated fats

Answer 5

Two or more double bonds between carbons in the hydrocarbon tail

Question 6

Phospholipid

Answer 6

A glycerol molecule with two fatty acid groups and one phosphate group.
The phosphate group is hydrophilic, there is a phospholipid bilayer in cell membranes

Question 7

Cholesterol

Answer 7

Has a hydrocarbon ring structure attached to a hydrocarbon tail.
The ring structure has a polar hydroxyl group attached.
In eukaryotic cells cholesterol strengthens the cell membrane by interacting with the phospholipid bilayer.
Small size and flat shape fits between phospholipid molecules, they bond to the hydrophobic tails packing them close together

Question 8

Emulsion test for lipids

Answer 8

1) shake the subject with ethanol for one minute And pour the solution into water
Lipid present- milky
Not present- clear

Question 9

Benedict’s test for reducing sugars

Answer 9

1) add Benedict’s reagent (blue) to a sample and heat in a boiling water bath.
Colour changes for blue to brick red
If RS present- closer to brick red
Not present- blue (no change)

Question 10

Benedict’s test non reducing sugars

Answer 10

If reducing is negative there still may be non reducing
1) get a new same of the solution and add dilute hydrochloric acid and boil for one minute.
2) allow the tube to cool then neutralise with sodium hydrogen carbonate.
4) leave in the bath for five minutes then observe the colour changes
(Same as reducing sugars, to brick red)