AP BIOLOGY

Detailed explanation-1: -(a) Ribosomes are larger than that of cytoplasmic ribosomes. (b) Two membranes have their own specific enzymes. (c) Matrix has single stranded, circular, naked DNA molecule.

Detailed explanation-2: -Mitochondrial ribosomes that more closely resemble prokaryotic ribosomes than cytoplasmic ribosomes of the cells in which they are found, though they are even smaller (55S) and have fewer proteins than bacterial ribosomes.

Detailed explanation-3: -For protein-synthesizing activity with a natural mRNA, mitochondrial ribosomes use tRNA from any cell compartment and are partly active with supernatant enzymes from cytoplasm. Cytoplasmic ribosomes are partly active with enzymes and tRNA from mitochondria or chloroplasts.

Detailed explanation-4: -Mammalian mitoribosomes have small 28S and large 39S subunits, together forming a 55S mitoribosome. Plant mitoribosomes have small 33S and large 50S subunits, together forming a 78S mitoribosome.

Detailed explanation-5: -Mammalian mitochondrial ribosomes contain smaller RNAs than do bacterial ribosomes and they also lack the 5S component found in most other ribosomes. The 12S RNA in the small subunit of human mitochondrial ribosomes is only 954 nucleotides long (323 kDa). As such, it is about 40% shorter than bacterial 16S RNA.