(i) Nucleus controls the functions of a cell. (ii) Cell membrane is like a policeman which does not allow everything and anything into and out of the cell.

nucleus

The nucleus is the control center of the cell that contains the chromosomes with their genetic material, DNA. The nucleus controls all cellular functions.

the powerhouses

A variety of genes are involved in the control of cell growth and division. Tight regulation of this process ensures that a dividing cell’s DNA is copied properly, any errors in the DNA are repaired, and each daughter cell receives a full set of chromosomes. …

Free and membrane-bound ribosomes produce different proteins. Whereas membrane-bound ribosomes produce proteins that are exported from the cell to be used elsewhere, free ribosomes produce proteins used inside the cell itself.

Ribosomes are made up of ribosomal proteins and ribosomal RNA (rRNA). In prokaryotes, ribosomes are roughly 40 percent protein and 60 percent rRNA. In eukaryotes, ribosomes are about half protein and half rRNA.

Proteins called reticulons and DP1/Yop1p play an important role in this stabilization. These proteins are integral membrane proteins that form oligomers to shape the lipid bilayer. In addition, they also use a structural motif that gets inserted into one leaflet of the membrane and increases its curvature.

There are two types of ribosomes, free and fixed (also known as membrane bound). They are identical in structure but differ in locations within the cell. Free ribosomes are located in the cytosol and are able to move throughout the cell, whereas fixed ribosomes are attached to the rER.

Ribosomes have two main functions — decoding the message and the formation of peptide bonds. These two activities reside in two large ribonucleoprotein particles (RNPs) of unequal size, the ribosomal subunits. Each subunit is made of one or more ribosomal RNAs (rRNAs) and many ribosomal proteins (r-proteins).

A ribosome itself looks like a little hamburger bun. It’s made of two subunits: a big one (the top bun) and a small one (the bottom bun). Eukaryotic ribosomes are found floating freely in the cytoplasm or attached to the rough endoplasmic reticulum (RER or rough ER for short).

The ‘S’ in the equation is Svedberg units which is a measure of how fast the particle sediments in an ultra-centrifuge. While the larger subunit sediments at 50S and the smaller at 30S together they sediment at 70S. Hence 50S+30S=70S and not 80S.

sedimentation rate

Eukaryotic ribosomes are also known as 80S ribosomes, referring to their sedimentation coefficients in Svedberg units, because they sediment faster than the prokaryotic (70S) ribosomes.

It’s called so, because it’s a tribute to Theodor Svedberg, winner of the Nobel Prize for Chemistry in 1926. Now back to our question, the extra 10S is the overlapping part of the subunits, hence, 50S+30S= 80S-10S= 70S.

It was expected that organellar ribosomes would be 70S particles, reminiscent of their ancestral prokaryotic origins. However, human (mammalian) mito- chondria contain 55S ribosomes (3).

Difference # 70S Ribosomes: 70S ribosomes are found both in prokaryotes and eukaryotes. 2. The ribosomes are found freely inside the cytoplasm of prokaryotes and matrix of plastids and mitochondria of eukaryotes.

All prokaryotes have 70S (where S=Svedberg units) ribosomes while eukaryotes contain larger 80S ribosomes in their cytosol. The 70S ribosome is made up of a 50S and 30S subunits. Ribosomes play a key role in the catalysis of two important and crucial biological processes. peptidyl transfer and peptidyl hydrolysis.

Eukaryotic ribosomes are also known as 80S ribosomes, referring to their sedimentation coefficients in Svedberg units, because they sediment faster than the prokaryotic (70S) ribosomes. Both subunits contain dozens of ribosomal proteins arranged on a scaffold composed of ribosomal RNA (rRNA).

Mitochondria and Chloroplasts both have 70s Ribosome, since they are evolved from prokaryotic bacteria and developed a symbiotic relationship with the cell.