Question

Describe the three major types of cellular organization in eukaryotic microbes.

Answer 1

1. Nucleus:

• True nucleus with nuclear membrane, nucleolus, chromosomes.'
• DNA replication occurs in chromosomes within the nucleus. DNA polymerase helps in polymerization of nucleotides to form DNA.
• Transcription occurs in nucleus followed by translation and modifications in cytoplasm.
• Three separate RNA polymerases:a. RNA pol I- synthesizes rRNA.b. RNA pol II- synthesizes mRNA.c. RNA pol II- synthesizes tRNA and other small RNAs.

2. Ribosome

• Molecular weight- 42000kD
• Sedimentation co-efficient-80s
• Subunits:
• larger subunit- 60s
• Smaller subunit- 40s
• rRNA (in larger subunit)-28s, 5.3s, 5s

3.

Endoplasmic reticulum

· Forms cellular skeletan and helps in compartmentalization of cell.

· De Novo biosynthesis of steroid, like cholesterol occurs in the smooth endoplasmic reticulum, as it contains the major enzymes required for the synthesis of membrane.

· The secretory pathway involves the movement and modification of proteins through specific membrane bound organelles and vesicles: like, from endoplasmic reticulum lumen, through transport vesicles, to cis-Golgi network, followed by trans-Golgi network.