Question

1. You need to design a drug that kills bacteria without harming human cells. Name 2 cell structures (Cell composition/ parts) that you would consider a potential "targets" for your drug. Briefly explain why you chose each structure.

2. based on your knowledge of certain type(s) organic molecules, why do you think cells have to be maintained at a constant temperature and pH.

3. Give two different examples of using cell wall structure to tell different organism apart.

Answer 1

1.One target can be cell wall of bacteria made up of peptidoglycan.

Peptidoglycan is itself made up of amino sugars and short peptides. Human cells do not make or need peptidoglycan.

Penicillin, one of the first antibiotics to be used widely, prevents the final cross-linking step, or transpeptidation, in assembly of this macromolecule, peptidoglycan. It kills bacteria but don't harm human cell.

Another target can be 30s ribosomal subunit in the process of protein synthesis in bacteria. Antibiotic named tetracycline inhibits bacterial growth by stopping protein synthesis. Both bacteria and humans carry out protein synthesis on structures called ribosomes. Tetracycline can cross the membranes of bacteria and accumulate in high concentrations in the cytoplasm. Tetracycline then binds to a single site on the ribosome-the 30S (smaller) ribosomal subunit--and blocks a key RNA interaction, which shuts off the lengthening protein chain. In human cells, however, tetracycline does not accumulate in sufficient concentrations to stop protein synthesis.

2.Cell organelles must be maintained at an appropriate pH in order to get the optimal function of each of the organelle . Again most of the enzymes can do their job only at a certain level of pH. Cells secrete acids and bases to maintain the proper pH for enzymes to work properly.

Body temperature must be controlled within a very narrow range so that the body can function properly. In particular, enzymes in a body's cells must have the correct temperature to be able to catalyse the chemical reactions to maintain our metabolism.

3.Examples are mentioned below.

i) Fungal cell wall is made up of chitin generally.

ii) Plant cell wall is made up of cellulose, hemi-cellulose, pectin.