🧫 Cytoplasm (Protoplasm / Cytosol)

What is Cytoplasm (Protoplasm / Cytosol)?

A semifluid substance inside the cell membrane.

What is the composition of cytoplasm?

Composed of ~80\% water, plus enzymes, ions, amino acids, and other molecules.

What are the main functions of cytoplasm?

Serves as the main site for biochemical and synthetic activities (e.g., metabolism, biosynthesis).

What analogy helps understand the function of cytoplasm?

The “workshop” of the cell where all reactions happen.

Where are ribosomes located?

Found free in the cytoplasm or attached to the inner cell membrane.

What is the function of ribosomes?

Sites of protein synthesis.

What is the composition of ribosomes?

~40\% protein + ~60\% ribosomal RNA (rRNA).

What are the subunits of a prokaryotic ribosome and their total Svedberg unit?

Made of two subunits: 30S (small subunit) and 50S (large subunit). Together form the 70S ribosome (S = Svedberg unit, based on sedimentation rate in centrifugation, not additive).

What are Polysomes (polyribosomes)?

Chains of ribosomes working together to translate a single mRNA molecule, making multiple copies of a protein at once.

Why is the difference between prokaryotic and eukaryotic ribosomes significant?

Prokaryotic ribosomes (70S) differ from eukaryotic ribosomes (80S), which is why certain antibiotics (like tetracycline, streptomycin) can target bacterial ribosomes without harming human cells.