Figure 17 shows colonies of bacteria growing on an agar plate - Edexcel - GCSE Biology - Question 9 - 2023 - Paper 1

Antibiotics are effective against bacterial infections because they specifically target mechanisms and structures unique to bacteria. This can include:

1. Cell Wall Synthesis: Many antibiotics disrupt the formation of the bacterial cell wall, leading to cell lysis and death.
2. Protein Synthesis: Antibiotics can interfere with bacterial protein synthesis by targeting ribosomal function, which is essential for bacterial growth and replication.

This selective toxicity means that while antibiotics kill or inhibit bacteria, they typically do not harm human cells.

To calculate the magnification of the drawing, we use the formula:

$\text{Magnification} = \frac{\text{length of the drawing}}{\text{actual length}}$

In this case, the length of the drawing is 80 mm, and the actual length of the bacterium is 0.005 mm. Therefore,

$\text{Magnification} = \frac{80 \text{ mm}}{0.005 \text{ mm}} = 16000$

Thus, the magnification of the drawing is 16000.

Bacterial cells and plant cells share some similarities but also have key differences:

Similarities:

• Both cell types are fundamental units of life and contain genetic material.
• They both have cytoplasm, where cellular processes occur, and ribosomes for protein synthesis.

Differences:

1. Cell Wall Composition:

   • Bacterial Cells: Have a peptidoglycan cell wall which provides structure and protection.
   • Plant Cells: Have a cellulose cell wall that gives rigidity and shape.

2. Nucleus:

   • Bacterial Cells: Do not have a true nucleus; their genetic material is located in the nucleoid region.
   • Plant Cells: Contain a well-defined nucleus enclosed within a nuclear membrane.

3. Size:

   • Bacterial Cells: Generally much smaller (0.1 - 10 micrometers).
   • Plant Cells: Typically larger (10 - 100 micrometers).

4. Organelles:

   • Bacterial Cells: Lack membrane-bound organelles.
   • Plant Cells: Have various organelles, including chloroplasts for photosynthesis and mitochondria for energy production.

These differences reflect their distinct roles in ecosystems and their methods of obtaining nutrients.