Question

(1). Please discuss the similarity and differences of mitochondria and chloroplasts.

(2). What are the structure and function of a ribosome? Where are ribosomes produced and assembled?

(3). What are the differences of microfilaments, intermediate filaments and microtubules ? What are the consequences that caused by their malfunctioning?

Answer 1

Q1) Similarities and differences of mitochondria and chloroplasts.

Similarities   - A double membrane surrounding the organelles.

- Purportedly prokaryotic origins according to the endosymbiotic theory which suggests that mitochondria and chloroplast were once prokaryotic bacteria engulfed by endocytosis in early eukaryotes.

- Their own circular DNA which codes for certain enzymes required for the chemical reactions that take place in these organelles.

- Their own 70S ribosomes made up of 50S and 30S subunits to translate proteins.

- Both organelles have chemical cycles in which the initial acceptor is regenerated at the end of the cycle. In mitochondria, the Krebs cycle occurs after which oxaloacetate is regenerated at the end of the reaction. In chloroplasts, the Calvin cycle occurs in which ribulose bisphosphate (RuBP) is regenerated at the end of the reaction.

Differences:- - Mitochondria are involved in cellular respiration whereas chloroplasts are involved in photosynthesis. Thus, the overall chemical reactions for the processes occurring in them are different and reversed.

- Electron transport chains: The final electron acceptor in mitochondria is oxygen, whereas the final electron acceptor in chloroplasts is NADP.

- Mitochondria function under both light and dark conditions. Chloroplasts, on the other hand, do need light to function.

- Chloroplasts contain pigments such as chlorophyll a, chlorophyll b and carotenoids. Mitochondria do not contain any such pigments.

- The types of electron acceptors present in mitochondria and chloroplast vary. While mitochondria contain NAD and FAD, chloroplasts contain NADP.

- Mitochondria function under both light and dark conditions. Chloroplasts, on the other hand, do need light to function.