Name any three sub-units of carbohydrates.

Here's the breakdown of your questions:

1.

a) Three sub-units of carbohydrates are:

1. Glucose
2. Fructose
3. Galactose

b) The positive colour for a reducing sugar test (e.g., Benedict's test) is a brick-red precipitate.

c)

(i) The word equation for the digestion of fats is:

$$\text{Fats} + \text{Water} \xrightarrow{\text{Lipase}} \text{Fatty acids} + \text{Glycerol}$$

(ii) To perform the emulsion test for fats:

1. Place a small amount of the food sample into a test tube.
2. Add about $2~\text{cm}^3$ of ethanol to the test tube and shake vigorously to dissolve any fats.
3. Carefully pour the ethanol solution into another test tube containing about $2~\text{cm}^3$ of distilled water.
4. If fats are present, a cloudy white emulsion will form. If no fat is present, the solution will remain clear.

d) One use of fats in living organisms is for energy storage. Fats store more than twice the energy per gram compared to carbohydrates or proteins.

2.

a)

• A solution is a homogeneous mixture composed of two or more substances, where one substance (the solute) is uniformly dispersed and dissolved in another substance (the solvent).
• Plasmolysis is the process in plant cells where the protoplast (the cell membrane and its contents) shrinks and pulls away from the cell wall due to the loss of water through osmosis when the cell is placed in a hypertonic (more concentrated) solution.

b)

(i) The biological process being investigated is osmosis.

(ii) After several hours, the level of the liquid in the glass tube will rise above A. This is because the solution inside the thistle funnel is more concentrated than the distilled water in the beaker. Water molecules will move by osmosis from the region of higher water potential (distilled water in the beaker) across the partially permeable membrane into the region of lower water potential (the solution inside the thistle funnel), causing the volume of liquid in the tube to increase.