▶️ Answer/Explanation
6(a)(i) Genus: Lactobacillus
Explanation: In binomial nomenclature, the first name is the Genus (capitalized) and the second is the species.
6(a)(ii) Usefulness: Rapid reproduction rate; ability to make complex molecules (e.g., enzymes/acids).
Explanation: Bacteria are ideal for biotechnology because they grow extremely fast under the right conditions and have simple genetic structures that allow them to produce specific chemicals, like lactic acid, which thickens milk into yoghurt.
6(b)(i) Calculation:
Mass of protein in $200\text{ g}$ of yoghurt: $7\text{ g}$ ($3.5\text{ g} \times 2$)
Mass of additional protein needed: $38\text{ g}$ ($45\text{ g} – 7\text{ g}$)
Explanation: Since the table provides data for $100\text{ g}$, we double the protein for $200\text{ g}$. Subtracting what was already eaten from the goal of $45\text{ g}$ gives the remaining requirement.
6(b)(ii) Importance of fats: Source/store of energy; insulation; protection of vital organs.
Explanation: Fats provide a concentrated energy source ($37\text{ kJ/g}$). They also form a layer of adipose tissue that keeps us warm and cushions internal organs from physical damage.
6(b)(iii) Source of fibre: Whole grain products, fruit, vegetables, beans, or nuts.
Explanation: Fibre (cellulose) comes from plant cell walls, which is why it is found in plant-based foods rather than animal products like yoghurt.
6(c)(i) Equation: $\text{glucose} \rightarrow \text{alcohol (ethanol)} + \text{carbon dioxide}$
Explanation: In the absence of oxygen, yeast breaks down sugar into ethanol and $CO_2$. This is also known as fermentation.
6(c)(ii) Role in bread: Carbon dioxide gas is produced which gets trapped in the dough, making it rise.
Explanation: The $CO_2$ bubbles expand during baking, creating the light, airy texture of bread. The alcohol produced usually evaporates during the baking process.
6(c)(iii) Other use: Production of biofuel (ethanol).
Explanation: Yeast is used on an industrial scale to ferment plant sugars into ethanol, which is used as a renewable alternative to fossil fuels.