Ribosomes are the translational apparatus of the cell with two major components the small ribosomal subunit which reads the RNA, and the large subunit which joins amino acids to form a polypeptide chain. Each subunit is composed of one or more rRNA molecules and a variety of proteins. It is devoid of any membrane.

6 Cell Organelles

• Nucleus. nucleus; animal cell.
• Ribosomes. Ribosomes are the protein factories of the cell.
• Endoplasmic reticulum. Ribosomes on the outer surface of the endoplasmic reticulum play an important role in protein synthesis within cells.
• Golgi apparatus. Golgi apparatus.
• Chloroplasts. chloroplast structure.
• Mitochondria.

The inner membrane is loaded with the proteins that make up the electron transport chain and help generate energy for the cell. The double membrane enclosures of mitochondria and chloroplasts are similar to certain modern-day prokaryotes and are thought to reflect these organelles’ evolutionary origins.

Most eukaryotic cells contain: Nucleus – which contains DNA and controls the synthesis of proteins. The nucleus contains a nucleolus, which is a dense body where ribosomes are made. The nucleus is surrounded by a double membrane, known as the nuclear envelope, with nuclear pores.

Several organelles of eukaryotic cells have a double membrane, Including chloroplasts and mitochondria, in which there are present an outer and an inner membrane, both which consists of lipid bilayers. So the difference between a lipid bilayer and a double membrane lies in the number of lipid bilayers present.

The lipid bilayer is the barrier that keeps ions, proteins and other molecules where they are needed and prevents them from diffusing into areas where they should not be.

The asymmetry of the cell membrane allows the membrane to be rigid and allows the cell to have a different intracellular environment from the existing extracellular environment.

In biology, membrane fluidity refers to the viscosity of the lipid bilayer of a cell membrane or a synthetic lipid membrane. Lipid packing can influence the fluidity of the membrane.

If saturated fatty acids are compressed by decreasing temperatures, they press in on each other, making a dense and fairly rigid membrane. If unsaturated fatty acids are compressed, the “kinks” in their tails push adjacent phospholipid molecules away, which helps maintain fluidity in the membrane.

Cholesterol, another lipid composed of four fused carbon rings, is found alongside phospholipids in the core of the membrane. Membrane proteins may extend partway into the plasma membrane, cross the membrane entirely, or be loosely attached to its inside or outside face.