[Biology Class Notes] on Cytology Pdf

Cytology meaning is given as the study of cells as the fundamental units of living things. The very earliest phase of cytology starts with the English scientist named Robert Hooke’s microscopic investigations of cork in the year 1665. He noticed the dead cork cells and introduced the term “cell” to describe those.

There are many types of cytology such as urine cytology, sputum cytology, aspiration cytology, fluid cytology, brush cytology, imprint cytology, and more.

Origin of Cytology

In the 19th century, two Germans: the biologist Theodor Schwann (in 1839) and the botanist Matthias Schleiden (in 1838), were the first among to clearly state that cells are the fundamental particles of both animals and plants. The cell theory, in particular, has been amply verified and expanded by a number of observations and interpretations. In the year 1892, the German embryologist and anatomist named Oscar Hertwig suggested that organismic processes are the reflections of cellular processes; he, therefore, established cytology as a separate branch of the biology subject.

Research into the chromosomes’ activities led to the cytogenetic founding in the years 1902–04, when the American geneticist named Walter Sutton and the German zoologist named Theodor Boveri has demonstrated the connection between heredity and cell division. A few modern cytologists have adopted several methods of chemistry and physics to investigate cellular events.

Techniques

Modern cell biology study looks at various ways to culture and control cells outside of a living organism in order to learn more about physiology and human anatomy, as well as to improve medications. The techniques where the cells are studied have evolved. The advancements in techniques, microscopy, and technology have allowed some scientists to gain a better understanding of the function and structure of cells. 

Commonly, Several Techniques are used to Study cell Biology, and a few are Listed below:

It utilizes the rapidly growing cells on media that allows for an excess amount of a particular cell type and an efficient way to study the cells.

• Fluorescence Microscopy: 

Here, fluorescent markers like GFP are used to label a particular cell’s components. Afterwards, a certain light wavelength can be used to excite fluorescent markers, which then can be visualized.

• Phase-Contrast Microscopy: 

It uses the optical aspect of light to indicate the solid, liquid, and gas-phase changes as the differences in brightness.

By focusing snap and light shooting instances to form a 3-D image, this combines fluorescence microscopy with imaging.

Cell Classification and Composition

There exist two fundamental classifications of cells as given below:

• Prokaryotic cells

• Eukaryotic cells

The lack of a cell nucleus or other membrane-bound organelle separates prokaryotic cells from eukaryotic cells. Prokaryotic cells are the smallest type of life, being smaller than eukaryotic cells. Typically, the study of the eukaryotic cells is the major focus of cytologists, whereas the prokaryotic cells are given as the focus of microbiologists.

Prokaryotic Cells

Prokaryotic cells include Archaea and Bacteria and lack an enclosed cell nucleus. These both reproduce through binary fission. Bacteria, which is the most prominent type, have many various shapes, which include a primary rod and spherical-shaped. Bacteria are classed as either gram-negative or gram-positive based on the cell wall composition. The Bacterial structural features can be given as:

• Ribosomes: It is used for the RNA to protein translation.

• Flagella: It is a tail-like structure that helps the cell to move.

• Nucleoid: It is the area designated to hold all the genetic material in the circular structure.

Eukaryotic Cells

Eukaryotic cells can either be unicellular or multicellular and include plant, animal, protozoa, and fungi cells, where all contain organelles with different sizes and shapes. These specific cells are composed of the organelles given below:

Nucleus

Nucleus functions as a genome and the genetic information storage for the cell, comprising all the DNA organized in the chromosome form. It is surrounded by the nuclear envelope that includes the nuclear pores allowing for protein transportation between the inside and outside of the nucleus. Also, this is the site for replication of DNA and transcription of DNA to RNA as well. Thereafter, the RNA can be modified and transported out to the cytosol to be translated to the protein.

Nucleolus

The nucleolus structure is within the nucleus, usually spherical and dense in shape. It is also the site of ribosomal RNA (which is rRNA) synthesis needed for ribosomal assembly.

Processes

Cell Metabolism

Cell metabolism is quite necessary for the production of cell energy and thus its survival and includes several pathways. Whereas, for cellular respiration, once glucose is available, glycolysis takes place within the cell’s cytosol to form pyruvate. Pyruvate undergoes decarboxylation by using the multi-enzyme complex to produce acetyl CoA, which can readily be used in the TCA cycle to form FADH2 and NADH. These specific products are involved in the electron transport chain to form a proton gradient ultimately across the inner mitochondrial membrane.

Cell Communication and Signaling

Cell communication is very important for cell regulation and for cells to process information from the environment and respond accordingly. Communication can take place through direct cell contact or paracrine, autocrine, and endocrine signaling. Direct cell-cell contact is when a receptor on a cell binds a molecule attached to the membrane of the other cell. Endocrine signaling takes place through the molecules secreted into the bloodstream.