Tag: biology

Howard and Pelc divided cell cycle in four stage. The cell cycle is an ordered set of events, culminating in cell growth and division into two daughter cells. Non-dividing cells not considered to be in the cell cycle. The stages  are G$ _1$-S-G$ _2$-M. The G$ _1$ stage stands for "GAP 1". The S stage stands for "Synthesis". This is the stage when DNA replication occurs. The G$ _2$ stage stands for "GAP 2". The M stage stands for "mitosis", and is when and cytoplasmic division occur.

Sphaerosomes are single half unit membrane covered small spherical organelles which synthesize and store fats. The cell wall of bacteria is made up of glycocalyx (carbohydrate and amino acids). Chloroplasts are eukaryotic plant cell organelles which have an internal thylakoid membrane system. The thylakoid membranes carry out the light reactions part of photosynthesis. The chromosomes of a eukaryotic cells are called its karyotype. The diagrammatic representation of a cells karyotype is called an idiogram.

Cell wall was discovered by Robert Hooke, in 1665, when he saw an empty box like compartments in a very thin slice of cork under his microscope. He wrote a book Micrographia and coined the term Cellula which was later on changed into cells. Robert Hooke thought cells to be passages for conducting fluids. Actually, he had observed compartments made up of the cell wall and not true living cells.