Give definitions of the following
(i) Endoplasmic Reticulum (ii) Ribosomes (iii) Nucleus (iv) Mitochondria

Endoplasmic Reticulum

Endoplasmic reticulum (ER), in biology, a continuous membrane system that forms a series of flattened sacs within the cytoplasm of eukaryotic cells and serves multiple functions, being important particularly in the synthesis, folding, modification, and transport of proteins.

Ribosomes

A sphere-shaped structure within the cytoplasm of a cell that is composed of RNA and protein and is the site of protein synthesis. Ribosomes are free in the cytoplasm and often attached to the membrane of the endoplasmic reticulum. Ribosomes exist in both eukaryotic and prokaryotic cells.

Nucleus

The nucleus is an organelle found in eukaryotic cells. Inside its fully enclosed nuclear membrane, it contains the majority of the cell's genetic material. This material is organized as DNA molecules, along with a variety of proteins, to form chromosomes.

The Image below shows parts of a Nucleus

Mitochondria

Mitochondria are known as the powerhouses of the cell. They are organelles that act like a digestive system that takes in nutrients, breaks them down, and creates energy-rich molecules for the cell. The biochemical processes of the cell are known as cellular respiration.

The Image below shows Mitochondrion