Page 15 - Cell biology PDG 2024

the production of subunits of the ribosomes. Therefore, nucleolus
plays an important role in protein synthesis and the production of
ribosomes in eukaryotic cells.
 Nucleoplasm: also known as karyoplasm. The nucleoplasm is a
type of protoplasm. The nucleoplasm includes the chromosomes
and nucleolus. Many substances such as nucleotides (necessary for
purposes such as DNA replication) and enzymes (which direct
activities that take place in the nucleus) are dissolved in the
nucleoplasm.
 Chromatin: nuclear DNA is not free linear strands; it is highly
condensed and wrapped around nuclear proteins (histones) in order
to fit inside the nucleus.

B) Ribosomes

They are the protein factories of the cell . It is largely made up of
specialized RNA known as ribosomal RNA (rRNA) as well as many
proteins .

The ribosomal proteins and rRNAs are arranged into two distinct
ribosomal pieces of different size, known generally as the large and small
subunit of the ribosome.

Ribosomes consist of two subunits that fit together and work as one to
translate the mRNA into a polypeptide chain during protein synthesis

The prokaryotic ribosome (70s) consists of 30s and 50s subunits while
the eukaryotic ribosome (80s) consists of 60s and 40s subunits.

C) Endoplasmic Reticulum (ER)

It appears as an interconnection of tubules that are connected to the
nuclear membrane in eukaryotic cells.

There are two types of ER based on the presence or absence of ribosomes
on them:

Rough ER (RER) with ribosomes attached on the cytosolic face of
Endoplasmic Reticulum and thus is involved in protein synthesis

Smooth ER (SER) which lacks ribosomes and has a function during lipid
synthesis.

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