Tag: cell and cell organelles

Chloroplasts have internal membranes called thylakoids suspended in ground substance called stroma. The thylakoids are of two types : appressed and non-appressed. The appressed membranes are stacked like a pile of coins called grana. The thylakoid membranes enclose small chambers. This thylakoid membrane system is absent in mitochondria. In mitochondria, the inner mitochondrial membrane is folded into cristae.

Internally, the chloroplast has two main components; the thylakoid lamellae and stroma. The stroma contains enzymes of Calvin cycle and carries out the dark reaction. The light reaction is carried out by thylakoid lamellae arranged as grana. Carotenes and chlorophyll pigments are present in the grana. These pigments are involved in capturing light energy for the light reaction. The inner space of mitochondria is filled with mitochondrial matrix.

A eukaryotic cell has DNA in nucleus as well as cell organelles like mitochondria and chloroplasts. The DNA in cell organelles resembles prokaryotic DNA. The organelle DNA is present as a circular molecule while the DNA in nucleus is organised as linear structures.

DNA is a long polymer made from repeating units called as nucleotides. DNA is found in mitochondria, plastid & nucleolus. Eukaryotic organisms like animals, plants, fungi, and protists store most of their DNA inside the cell nucleus and some of their DNA in organelles, such as mitochondria or chloroplasts. In contrast, prokaryotes like bacteria and archaea store their DNA only in the cytoplasm. 

Extrachromosomal DNA is found in chloroplast and mitochondria. Extrachromosomal DNA is any DNA that is found outside of the nucleus of a cell. It is also referred to as extranuclear DNA  or cytoplasmic DNA. Most DNA in an individual genome is found in chromosomes. Extrachromosomal DNA is often used in research of replication because it is easy to identify and isolate.

Extrachromosomal DNA is any DNA that is found outside of the nucleus of a cell. It is also referred to as extranuclear DNA or cytoplasmic DNA. This extra chromosomal DNA is present in both mitochondria and chloroplast. Chloroplast and mitochondria are present in the plant cell but chloroplast is absent in the animal cell. They both are present in eukaryotic cells.

Option b is incorrect because a  thylakoid is a membrane-bound compartment inside chloroplasts and cyanobacteria and not present in the mitochondrion. They are the site of the light-dependent reactions of photosynthesis. Thylakoids consist of a thylakoid membrane surrounding a thylakoid lumen. Chloroplast thylakoids frequently form stacks of disks referred to as grana. Grana are connected by intergranal or stroma thylakoids, which join granum stacks together as a single functional compartment.

According to the endosymbiotic theory about origin of chloroplast and mitochondria, both of these cell organelles were independent organisms that became lodged inside a eukaryotic cell during evolution.